OpenSimplexNoise

'/*
' * OpenSimplex Noise in FreeBASIC.
' * by Kurt Spencer
' *
' * v1.1 (October 5, 2014)
' * - Added 2D and 4D implementations.
' * - Proper gradient sets for all dimensions, from a
' *   dimensionally-generalizable scheme with an actual
' *   rhyme and reason behind it.
' * - Removed default permutation array in favor of
' *   default seed.
' * - Changed seed-based constructor to be independent
' *   of any particular randomization library, so results
' *   will be the same when ported to other languages.
' */

type OpenSimplexNoise extends INoise
    Public:
    Declare Constructor()
    Declare Constructor(seed As LongInt)
    Declare Destructor()
    Declare Function noise(x As Double ,y As double) As Double
    Declare Function noise(x As Double ,y As Double, z As double) As Double
    Declare Function noise(x As Double ,y As double, z As Double, w As Double) As Double
    Private:
    Declare Function fastfloor(x As double) As Integer
    Declare Function extrapolate2(xsb As Integer, ysb As Integer, dx As Double, dy As Double) As Double
    Declare Function extrapolate3(xsb As Integer, ysb As Integer, zsb As Integer, dx As Double, dy As Double, dz As Double)As Double
    Declare Function extrapolate4(xsb As integer, ysb As Integer, zsb As Integer, wsb As Integer, dx As Double, dy As Double, dz As Double, dw As Double)As Double

    dim as double STRETCH_CONSTANT_2D = -0.211324865405187    ''(1/sqr(2+1)-1)/2
    dim As double SQUISH_CONSTANT_2D = 0.366025403784439      ''(sqr(2+1)-1)/2
    dim As double STRETCH_CONSTANT_3D = -1.0 / 6.0              ''(1/sqr(3+1)-1)/3
    dim As double SQUISH_CONSTANT_3D = 1.0 / 3.0                ''(sqr(3+1)-1)/3
    dim As double STRETCH_CONSTANT_4D = -0.138196601125011    ''(1/sqr(4+1)-1)/4
    dim As double SQUISH_CONSTANT_4D = 0.309016994374947      ''(sqr(4+1)-1)/4

    dim As double NORM_CONSTANT_2D = 47
    dim As double NORM_CONSTANT_3D = 103
    dim As double NORM_CONSTANT_4D = 30

    dim as uLongint DEFAULT_SEED = 0

    Dim As Short Ptr perm
    Dim As Short ptr permGradIndex3D

    ''Gradients for 2D. They approximate the directions to the
    ''vertices of an octagon from the center.
    Dim As byte gradients2D(8,2) = {_
    {5,  2},   {2,  5},_
    {-5,  2},   {-2,  5},_
    {5, -2},    {2, -5},_
    {-5, -2},   {-2, -5} _
    }

    ''Gradients for 3D. They approximate the directions to the
    ''vertices of a rhombicuboctahedron from the center, skewed so
    ''that the triangular and square facets can be inscribed inside
    ''circles of the same radius.
    Dim As byte gradients3D(24,3) = {_
    {-11,  4,  4},    { -4,  11,  4},   { -4,  4,  11},_
    {11,  4,  4},     { 4,  11,  4},    { 4,  4,  11},_
    {-11, -4,  4},    { -4, -11,  4},   { -4, -4,  11},_
    {11, -4,  4},      {4, -11,  4},     {4, -4,  11},_
    {-11,  4, -4},    { -4,  11, -4},   {-4,  4, -11},_
    {11,  4, -4},      {4,  11, -4},    { 4,  4, -11},_
    {-11, -4, -4},    {-4, -11, -4},    {-4, -4, -11},_
    {11, -4, -4},      {4, -11, -4},    { 4, -4, -11} _
    }

    ''Gradients for 4D. They approximate the directions to the
    ''vertices of a disprismatotesseractihexadecachoron from the center,
    ''skewed so that the tetrahedral and cubic facets can be inscribed inside
    ''spheres of the same radius.
    Dim As Byte gradients4D(64,4) = {_
    {3,  1,  1,  1},     { 1,  3,  1,  1},     { 1,  1,  3,  1},     { 1,  1,  1,  3},_
    {-3,  1,  1,  1},    { -1,  3,  1,  1},    { -1,  1,  3,  1},    { -1,  1,  1,  3},_
    {3, -1,  1,  1},     { 1, -3,  1,  1},     { 1, -1,  3,  1},     { 1, -1,  1,  3},_
    {-3, -1,  1,  1},    { -1, -3,  1,  1},    { -1, -1,  3,  1},    { -1, -1,  1,  3},_
    {3,  1, -1,  1},     { 1,  3, -1,  1},     { 1,  1, -3,  1},     { 1,  1, -1,  3},_
    {-3,  1, -1,  1},    { -1,  3, -1,  1},    { -1,  1, -3,  1},    { -1,  1, -1,  3},_
    {3, -1, -1,  1},     { 1, -3, -1,  1},     { 1, -1, -3,  1},     { 1, -1, -1,  3},_
    {-3, -1, -1,  1},    { -1, -3, -1,  1},    { -1, -1, -3,  1},    { -1, -1, -1,  3},_
    {3,  1,  1, -1},      {1,  3,  1, -1},     { 1,  1,  3, -1},     { 1,  1,  1, -3},_
    {-3,  1,  1, -1},     {-1,  3,  1, -1},    { -1,  1,  3, -1},    { -1,  1,  1, -3},_
    {3, -1,  1, -1},      {1, -3,  1, -1},     { 1, -1,  3, -1},     { 1, -1,  1, -3},_
    {-3, -1,  1, -1},     {-1, -3,  1, -1},    { -1, -1,  3, -1},    { -1, -1,  1, -3},_
    {3,  1, -1, -1},      {1,  3, -1, -1},     { 1,  1, -3, -1},     { 1,  1, -1, -3},_
    {-3,  1, -1, -1},    { -1,  3, -1, -1},    { -1,  1, -3, -1},    { -1,  1, -1, -3},_
    {3, -1, -1, -1},     { 1, -3, -1, -1},     { 1, -1, -3, -1},     { 1, -1, -1, -3}, _
    {-3, -1, -1, -1},     {-1, -3, -1, -1},    { -1, -1, -3, -1},    { -1, -1, -1, -3} _
    }
End type


Constructor OpenSimplexNoise()
Dim seed As ULongInt=DEFAULT_SEED
perm = new Short[256]
permGradIndex3D = new Short[256]
Dim As Short Ptr source = new Short[256]
for i As Integer=0 To 255
    source[i] = i
next
seed = seed * 6364136223846793005ull + 1442695040888963407ull
seed = seed * 6364136223846793005ull + 1442695040888963407ull
seed = seed * 6364136223846793005ull + 1442695040888963407ull
for i As Integer=255 To 0 Step -1
    seed = seed * 6364136223846793005ull + 1442695040888963407ull
    Dim As integer r = Int((seed + 31) Mod (i + 1))
    if (r < 0) Then
        r += (i + 1)
    EndIf
    perm[i] = source[r]
    permGradIndex3D[i] = Cast(Short,((perm[i] Mod (24)) ))
    source[r] = source[i]
Next
Delete [] source
source=0
End Constructor

''Initializes the class using a permutation array generated from a 64-bit seed.
''Generates a proper permutation (i.e. doesn't merely perform N successive pair swaps on a base array)
''Uses a simple 64-bit LCG.
Constructor OpenSimplexNoise(seed As LongInt)
perm = new short[256]
permGradIndex3D = new short[256]
Dim As Short Ptr source = new short[256]
for i As UInteger=0 To 255
    source[i] = i
next
seed = seed * 6364136223846793005ull + 1442695040888963407ull
seed = seed * 6364136223846793005ull + 1442695040888963407ull
seed = seed * 6364136223846793005ull + 1442695040888963407ull
for i As Integer=255 To 0 Step -1
    seed = seed * 6364136223846793005ull + 1442695040888963407ull
    Dim As integer r = Int((seed + 31) Mod (i + 1))
    if (r < 0) Then
        r += (i + 1)
    EndIf
    perm[i] = source[r]
    permGradIndex3D[i] = cast(short,((perm[i] Mod (24)) ))
    source[r] = source[i]
Next
Delete [] source
source=0
End Constructor
Destructor OpenSimplexNoise()
Delete [] perm
perm=0
Delete [] permGradIndex3D
permGradIndex3D=0
End Destructor
Function OpenSimplexNoise.fastfloor(x As double) As Integer
    return IIf(x>=0,Int(x) , Int(x-1))
End Function
Function OpenSimplexNoise.extrapolate2(xsb As Integer, ysb As Integer, dx As Double, dy As Double) As Double
    Dim As integer index = perm[(perm[xsb and &hFF] + ysb) and &hFF] Mod 8
    return gradients2D(index,0) * dx + gradients2D(index,1) * dy
End Function

Function OpenSimplexNoise.extrapolate3(xsb As Integer, ysb As Integer, zsb As Integer, dx As Double, dy As Double, dz As Double)As Double
    Dim As integer index = permGradIndex3D[(perm[(perm[xsb And &hFF] + ysb) And &hFF] + zsb) And &hFF] Mod 24
    return gradients3D(index,0) * dx + gradients3D(index,1) * dy + gradients3D(index, 2) * dz
End Function

Function OpenSimplexNoise.extrapolate4(xsb As integer, ysb As Integer, zsb As Integer, wsb As Integer, dx As Double, dy As Double, dz As Double, dw As Double)As Double
    Dim As integer index = perm[(perm[(perm[(perm[xsb And &hFF] + ysb) And &hFF] + zsb) and &hFF] + wsb) And &hFF] Mod 64
    return gradients4D(index,0) * dx + gradients4D(index , 1) * dy + gradients4D(index , 2) * dz + gradients4D(index , 3) * dw
End function

''2D OpenSimplex Noise.
function  OpenSimplexNoise.noise(x As Double ,y As double) As Double

    ''Place input coordinates onto grid.
    Dim As Double stretchOffset = (x + y) * STRETCH_CONSTANT_2D
    Dim As Double xs = x + stretchOffset
    Dim As Double ys = y + stretchOffset

    ''Floor to get grid coordinates of rhombus (stretched square) super-cell origin.
    Dim As Integer xsb = fastFloor(xs)
    Dim As Integer ysb = fastFloor(ys)

    ''Skew out to get actual coordinates of rhombus origin. We'll need these later.
    Dim As Double squishOffset = (xsb + ysb) * SQUISH_CONSTANT_2D
    Dim As Double xb = xsb + squishOffset
    Dim As Double yb = ysb + squishOffset

    ''Compute grid coordinates relative to rhombus origin.
    Dim As Double xins = xs - xsb
    Dim As Double yins = ys - ysb

    ''Sum those together to get a value that determines which region we're in.
    Dim As Double inSum = xins + yins

    ''Positions relative to origin point.
    Dim As Double dx0 = x - xb
    Dim As Double dy0 = y - yb

    ''We'll be defining these inside the next block and using them afterwards.
    Dim As Double dx_ext, dy_ext
    Dim As Integer xsv_ext, ysv_ext

    Dim As Double value = 0

    ''Contribution (1,0)
    Dim As Double dx1 = dx0 - 1.0 - SQUISH_CONSTANT_2D
    Dim As Double dy1 = dy0 - 0.0 - SQUISH_CONSTANT_2D
    Dim As Double attn1 = 2.0 - (dx1 * dx1) - (dy1 * dy1)
    if (attn1 > 0.0) Then
        attn1 *= attn1
        value += (attn1 * attn1) * extrapolate2(xsb + 1, ysb + 0, dx1, dy1)
    EndIf

    ''Contribution (0,1)
    Dim As Double dx2 = dx0 - 0.0 - SQUISH_CONSTANT_2D
    Dim As Double dy2 = dy0 - 1.0 - SQUISH_CONSTANT_2D
    Dim As Double attn2 = 2.0 - dx2 * dx2 - dy2 * dy2
    if (attn2 > 0) Then
        attn2 *= attn2
        value += (attn2 * attn2) * extrapolate2(xsb + 0, ysb + 1, dx2, dy2)
    endif

    if (inSum <= 1.0) then ''We're inside the triangle (2-Simplex) at (0,0)
        Dim As Double zins = 1.0 - inSum
        if ((zins > xins) or (zins > yins)) then ''(0,0) is one of the closest two triangular vertices
            if (xins > yins) Then
                xsv_ext = xsb + 1.0
                ysv_ext = ysb - 1.0
                dx_ext = dx0 - 1.0
                dy_ext = dy0 + 1.0
            else
                xsv_ext = xsb - 1.0
                ysv_ext = ysb + 1.0
                dx_ext = dx0 + 1.0
                dy_ext = dy0 - 1.0
            EndIf
        Else ''(1,0) and (0,1) are the closest two vertices.
            xsv_ext = xsb + 1.0
            ysv_ext = ysb + 1.0
            dx_ext = dx0 - 1.0 - 2.0 * SQUISH_CONSTANT_2D
            dy_ext = dy0 - 1.0 - 2.0 * SQUISH_CONSTANT_2D
        EndIf
    else ''We're inside the triangle (2-Simplex) at (1,1)
        Dim As Double zins = 2.0 - inSum
        if ((zins < xins) or (zins < yins)) Then ''(0,0) is one of the closest two triangular vertices
            if (xins > yins) Then
                xsv_ext = xsb + 2.0
                ysv_ext = ysb + 0.0
                dx_ext = dx0 - 2.0 - 2.0 * SQUISH_CONSTANT_2D
                dy_ext = dy0 + 0.0 - 2.0 * SQUISH_CONSTANT_2D
            Else
                xsv_ext = xsb + 0.0
                ysv_ext = ysb + 2.0
                dx_ext = dx0 + 0.0 - 2.0 * SQUISH_CONSTANT_2D
                dy_ext = dy0 - 2.0 - 2.0 * SQUISH_CONSTANT_2D
            endif
        else  ''(1,0) and (0,1) are the closest two vertices.
            dx_ext = dx0
            dy_ext = dy0
            xsv_ext = xsb
            ysv_ext = ysb
        EndIf
        xsb += 1.0
        ysb += 1.0
        dx0 = dx0 - 1.0 - 2.0 * SQUISH_CONSTANT_2D
        dy0 = dy0 - 1.0 - 2.0 * SQUISH_CONSTANT_2D
    EndIf

    ''Contribution (0,0) or (1,1)
    Dim As Double attn0 = 2.0 - dx0 * dx0 - dy0 * dy0
    if (attn0 > 0.0) Then
        attn0 *= attn0
        value += (attn0 * attn0) * extrapolate2(xsb, ysb, dx0, dy0)
    EndIf

    ''Extra Vertex
    Dim As Double attn_ext = 2.0 - dx_ext * dx_ext - dy_ext * dy_ext
    if (attn_ext > 0.0)Then
        attn_ext *= attn_ext
        value += (attn_ext * attn_ext) * extrapolate2(xsv_ext, ysv_ext, dx_ext, dy_ext)
    endif
    value/=NORM_CONSTANT_2D
    return value
End Function

''3D OpenSimplex Noise.
Function OpenSimplexNoise.noise(x As Double ,y As Double, z As double) As Double

    ''Place input coordinates on simplectic honeycomb.
    Dim As Double stretchOffset = (x + y + z) * STRETCH_CONSTANT_3D
    Dim As Double xs = x + stretchOffset
    Dim As Double ys = y + stretchOffset
    Dim As Double zs = z + stretchOffset

    ''Floor to get simplectic honeycomb coordinates of rhombohedron (stretched cube) super-cell origin.
    Dim As integer xsb = fastFloor(xs)
    Dim As Integer ysb = fastFloor(ys)
    Dim As Integer zsb = fastFloor(zs)

    ''Skew out to get actual coordinates of rhombohedron origin. We'll need these later.
    Dim As Double squishOffset = (xsb + ysb + zsb) * SQUISH_CONSTANT_3D
    Dim As Double xb = xsb + squishOffset
    Dim As Double yb = ysb + squishOffset
    Dim As Double zb = zsb + squishOffset

    ''Compute simplectic honeycomb coordinates relative to rhombohedral origin.
    Dim As Double xins = xs - xsb
    Dim As Double yins = ys - ysb
    Dim As Double zins = zs - zsb

    ''Sum those together to get a value that determines which region we're in.
    Dim As Double inSum = xins + yins + zins

    ''Positions relative to origin point.
    Dim As Double dx0 = x - xb
    Dim As Double dy0 = y - yb
    Dim As Double dz0 = z - zb

    ''We'll be defining these inside the next block and using them afterwards.
    Dim As Double dx_ext0, dy_ext0, dz_ext0
    Dim As Double dx_ext1, dy_ext1, dz_ext1
    Dim As Integer xsv_ext0, ysv_ext0, zsv_ext0
    Dim As Integer xsv_ext1, ysv_ext1, zsv_ext1

    Dim As Double value = 0
    if (inSum <= 1) Then ''We're inside the tetrahedron (3-Simplex) at (0,0,0)

        ''Determine which two of (0,0,1), (0,1,0), (1,0,0) are closest.
        Dim As Byte aPoint = &h01
        Dim As Double aScore = xins
        Dim As Byte bPoint = &h02
        Dim As Double bScore = yins
        if (aScore >= bScore And zins > bScore) Then
            bScore = zins
            bPoint = &h04
        elseif (aScore < bScore and zins > aScore) Then
            aScore = zins
            aPoint = &h04
        endif

        ''Now we determine the two lattice points not part of the tetrahedron that may contribute.
        ''This depends on the closest two tetrahedral vertices, including (0,0,0)
        Dim As Double wins = 1 - inSum
        if (wins > aScore Or wins > bScore) Then ''(0,0,0) is one of the closest two tetrahedral vertices.
            Dim As Byte c = iif(bScore > aScore , bPoint , aPoint) ''Our other closest vertex is the closest out of a and b.

            if ((c and &h01) = 0) Then
                xsv_ext0 = xsb - 1
                xsv_ext1 = xsb
                dx_ext0 = dx0 + 1
                dx_ext1 = dx0
            Else
                xsv_ext0 = xsv_ext1 = xsb + 1
                dx_ext0 = dx_ext1 = dx0 - 1
            endif

            if ((c and &h02) = 0) Then
                ysv_ext0 = ysv_ext1 = ysb
                dy_ext0 = dy_ext1 = dy0
                if ((c and &h01) = 0) Then
                    ysv_ext1 -= 1
                    dy_ext1 += 1
                Else
                    ysv_ext0 -= 1
                    dy_ext0 += 1
                endif
            Else
                ysv_ext0 = ysv_ext1 = ysb + 1
                dy_ext0 = dy_ext1 = dy0 - 1
            EndIf

            if ((c and &h04) = 0) then
                zsv_ext0 = zsb
                zsv_ext1 = zsb - 1
                dz_ext0 = dz0
                dz_ext1 = dz0 + 1
            Else
                zsv_ext0 = zsv_ext1 = zsb + 1
                dz_ext0 = dz_ext1 = dz0 - 1
            EndIf
        Else ''(0,0,0) is not one of the closest two tetrahedral vertices.
            Dim As Byte c = aPoint And bPoint'cast(Byte,(aPoint or bPoint)) ''Our two extra vertices are determined by the closest two.

            if ((c and &h01) = 0) Then
                xsv_ext0 = xsb
                xsv_ext1 = xsb - 1
                dx_ext0 = dx0 - 2 * SQUISH_CONSTANT_3D
                dx_ext1 = dx0 + 1 - SQUISH_CONSTANT_3D
            Else
                xsv_ext0 = xsv_ext1 = xsb + 1
                dx_ext0 = dx0 - 1 - 2 * SQUISH_CONSTANT_3D
                dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_3D
            EndIf

            if ((c and &h02) = 0) Then
                ysv_ext0 = ysb
                ysv_ext1 = ysb - 1
                dy_ext0 = dy0 - 2 * SQUISH_CONSTANT_3D
                dy_ext1 = dy0 + 1 - SQUISH_CONSTANT_3D
            Else
                ysv_ext0 = ysv_ext1 = ysb + 1
                dy_ext0 = dy0 - 1 - 2 * SQUISH_CONSTANT_3D
                dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_3D
            EndIf

            if ((c and &h04) = 0) Then
                zsv_ext0 = zsb
                zsv_ext1 = zsb - 1
                dz_ext0 = dz0 - 2 * SQUISH_CONSTANT_3D
                dz_ext1 = dz0 + 1 - SQUISH_CONSTANT_3D
            Else
                zsv_ext0 = zsv_ext1 = zsb + 1
                dz_ext0 = dz0 - 1 - 2 * SQUISH_CONSTANT_3D
                dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_3D
            endif
        endif

        ''Contribution (0,0,0)
        Dim As Double attn0 = 2 - dx0 * dx0 - dy0 * dy0 - dz0 * dz0
        if (attn0 > 0) Then
            attn0 *= attn0
            value += attn0 * attn0 * extrapolate3(xsb + 0, ysb + 0, zsb + 0, dx0, dy0, dz0)
        endif

        ''Contribution (1,0,0)
        Dim As Double dx1 = dx0 - 1 - SQUISH_CONSTANT_3D
        Dim As Double dy1 = dy0 - 0 - SQUISH_CONSTANT_3D
        Dim As Double dz1 = dz0 - 0 - SQUISH_CONSTANT_3D
        Dim As Double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1
        if (attn1 > 0) Then
            attn1 *= attn1
            value += attn1 * attn1 * extrapolate3(xsb + 1, ysb + 0, zsb + 0, dx1, dy1, dz1)
        EndIf

        ''Contribution (0,1,0)
        Dim As Double dx2 = dx0 - 0 - SQUISH_CONSTANT_3D
        Dim As Double dy2 = dy0 - 1 - SQUISH_CONSTANT_3D
        Dim As Double dz2 = dz1
        Dim As Double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2
        if (attn2 > 0) Then
            attn2 *= attn2
            value += attn2 * attn2 * extrapolate3(xsb + 0, ysb + 1, zsb + 0, dx2, dy2, dz2)
        EndIf

        ''Contribution (0,0,1)
        Dim As Double dx3 = dx2
        Dim As Double dy3 = dy1
        Dim As Double dz3 = dz0 - 1 - SQUISH_CONSTANT_3D
        Dim As Double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3
        if (attn3 > 0) Then
            attn3 *= attn3
            value += attn3 * attn3 * extrapolate3(xsb + 0, ysb + 0, zsb + 1, dx3, dy3, dz3)
        EndIf
    ElseIf (inSum >= 2) Then ''We're inside the tetrahedron (3-Simplex) at (1,1,1)

        ''Determine which two tetrahedral vertices are the closest, out of (1,1,0), (1,0,1), (0,1,1) but not (1,1,1).
        Dim As Byte aPoint = &h06
        Dim As Double aScore = xins
        Dim As Byte bPoint = &h05
        Dim As Double bScore = yins
        if (aScore <= bScore And zins < bScore) Then
            bScore = zins
            bPoint = &h03
        elseif (aScore > bScore And zins < aScore) Then
            aScore = zins
            aPoint = &h03
        endif

        ''Now we determine the two lattice points not part of the tetrahedron that may contribute.
        ''This depends on the closest two tetrahedral vertices, including (1,1,1)
        Dim As Double wins = 3 - inSum
        if (wins < aScore Or wins < bScore) Then ''(1,1,1) is one of the closest two tetrahedral vertices.
            Dim As uByte c = iif(bScore < aScore , bPoint , aPoint) ''Our other closest vertex is the closest out of a and b.

            if ((c and &h01) <> 0) then
                xsv_ext0 = xsb + 2
                xsv_ext1 = xsb + 1
                dx_ext0 = dx0 - 2 - 3 * SQUISH_CONSTANT_3D
                dx_ext1 = dx0 - 1 - 3 * SQUISH_CONSTANT_3D
            Else
                xsv_ext0 = xsv_ext1 = xsb
                dx_ext0 = dx_ext1 = dx0 - 3 * SQUISH_CONSTANT_3D
            EndIf

            if ((c and &h02) <> 0) Then
                ysv_ext0 = ysv_ext1 = ysb + 1
                dy_ext0 = dy_ext1 = dy0 - 1 - 3 * SQUISH_CONSTANT_3D
                if ((c and &h01) <> 0) Then
                    ysv_ext1 += 1
                    dy_ext1 -= 1
                Else
                    ysv_ext0 += 1
                    dy_ext0 -= 1
                EndIf
            Else
                ysv_ext0 = ysv_ext1 = ysb
                dy_ext0 = dy_ext1 = dy0 - 3 * SQUISH_CONSTANT_3D
            endif

            if ((c and &h04) <> 0) Then
                zsv_ext0 = zsb + 1
                zsv_ext1 = zsb + 2
                dz_ext0 = dz0 - 1 - 3 * SQUISH_CONSTANT_3D
                dz_ext1 = dz0 - 2 - 3 * SQUISH_CONSTANT_3D
            Else
                zsv_ext0 = zsv_ext1 = zsb
                dz_ext0 = dz_ext1 = dz0 - 3 * SQUISH_CONSTANT_3D
            EndIf
        Else ''(1,1,1) is not one of the closest two tetrahedral vertices.
            Dim As Byte c = aPoint And bPoint'cast(byte,(aPoint And bPoint)) ''Our two extra vertices are determined by the closest two.

            if ((c and &h01) <> 0) Then
                xsv_ext0 = xsb + 1
                xsv_ext1 = xsb + 2
                dx_ext0 = dx0 - 1 - SQUISH_CONSTANT_3D
                dx_ext1 = dx0 - 2 - 2 * SQUISH_CONSTANT_3D
            Else
                xsv_ext0 = xsv_ext1 = xsb
                dx_ext0 = dx0 - SQUISH_CONSTANT_3D
                dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_3D
            EndIf

            if ((c and &h02) <> 0) Then
                ysv_ext0 = ysb + 1
                ysv_ext1 = ysb + 2
                dy_ext0 = dy0 - 1 - SQUISH_CONSTANT_3D
                dy_ext1 = dy0 - 2 - 2 * SQUISH_CONSTANT_3D
            Else
                ysv_ext0 = ysv_ext1 = ysb
                dy_ext0 = dy0 - SQUISH_CONSTANT_3D
                dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_3D
            EndIf

            if ((c and &h04) <> 0) Then
                zsv_ext0 = zsb + 1
                zsv_ext1 = zsb + 2
                dz_ext0 = dz0 - 1 - SQUISH_CONSTANT_3D
                dz_ext1 = dz0 - 2 - 2 * SQUISH_CONSTANT_3D
            Else
                zsv_ext0 = zsv_ext1 = zsb
                dz_ext0 = dz0 - SQUISH_CONSTANT_3D
                dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_3D
            EndIf
        endif

        ''Contribution (1,1,0)
        Dim As Double dx3 = dx0 - 1 - 2 * SQUISH_CONSTANT_3D
        Dim As Double dy3 = dy0 - 1 - 2 * SQUISH_CONSTANT_3D
        Dim As Double dz3 = dz0 - 0 - 2 * SQUISH_CONSTANT_3D
        Dim As Double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3
        if (attn3 > 0) Then
            attn3 *= attn3
            value += attn3 * attn3 * extrapolate3(xsb + 1, ysb + 1, zsb + 0, dx3, dy3, dz3)
        EndIf

        ''Contribution (1,0,1)
        Dim As Double dx2 = dx3
        Dim As Double dy2 = dy0 - 0 - 2 * SQUISH_CONSTANT_3D
        Dim As Double dz2 = dz0 - 1 - 2 * SQUISH_CONSTANT_3D
        Dim As Double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2
        if (attn2 > 0) Then
            attn2 *= attn2
            value += attn2 * attn2 * extrapolate3(xsb + 1, ysb + 0, zsb + 1, dx2, dy2, dz2)
        EndIf

        ''Contribution (0,1,1)
        Dim As Double dx1 = dx0 - 0 - 2 * SQUISH_CONSTANT_3D
        Dim As Double dy1 = dy3
        Dim As Double dz1 = dz2
        Dim As Double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1
        if (attn1 > 0) Then
            attn1 *= attn1
            value += attn1 * attn1 * extrapolate3(xsb + 0, ysb + 1, zsb + 1, dx1, dy1, dz1)
        endif

        ''Contribution (1,1,1)
        dx0 = dx0 - 1 - 3 * SQUISH_CONSTANT_3D
        dy0 = dy0 - 1 - 3 * SQUISH_CONSTANT_3D
        dz0 = dz0 - 1 - 3 * SQUISH_CONSTANT_3D
        Dim As Double attn0 = 2 - dx0 * dx0 - dy0 * dy0 - dz0 * dz0
        if (attn0 > 0) Then
            attn0 *= attn0
            value += attn0 * attn0 * extrapolate3(xsb + 1, ysb + 1, zsb + 1, dx0, dy0, dz0)
        EndIf
    Else  ''We're inside the octahedron (Rectified 3-Simplex) in between.
        Dim As Double aScore
        Dim As Byte aPoint
        Dim As boolean aIsFurtherSide=FALSE
        Dim As Double bScore
        Dim As Byte bPoint
        Dim As boolean bIsFurtherSide=FALSE

        ''Decide between point (0,0,1) and (1,1,0) as closest
        Dim As Double p1 = xins + yins
        if (p1 > 1) Then
            aScore = p1 - 1
            aPoint = &h03
            aIsFurtherSide = TRUE
        Else
            aScore = 1 - p1
            aPoint = &h04
            aIsFurtherSide = FALSE
        EndIf

        ''Decide between point (0,1,0) and (1,0,1) as closest
        Dim As Double p2 = xins + zins
        if (p2 > 1) Then
            bScore = p2 - 1
            bPoint = &h05
            bIsFurtherSide = TRUE
        else
            bScore = 1 - p2
            bPoint = &h02
            bIsFurtherSide = FALSE
        EndIf

        ''The closest out of the two (1,0,0) and (0,1,1) will replace the furthest out of the two decided above, if closer.
        Dim As Double p3 = yins + zins
        if (p3 > 1) Then
            Dim As Double score = p3 - 1
            if (aScore <= bScore And aScore < score) Then
                aScore = score
                aPoint = &h06
                aIsFurtherSide = TRUE
            elseif (aScore > bScore And bScore < score) Then
                bScore = score
                bPoint = &h06
                bIsFurtherSide = TRUE
            EndIf
        Else
            Dim As Double score = 1 - p3
            if (aScore <= bScore And aScore < score) Then
                aScore = score
                aPoint = &h01
                aIsFurtherSide = FALSE
            ElseIf (aScore > bScore And bScore < score) Then
                bScore = score
                bPoint = &h01
                bIsFurtherSide = FALSE
            EndIf
        endif

        ''Where each of the two closest points are determines how the extra two vertices are calculated.
        if (aIsFurtherSide = bIsFurtherSide) Then
            if (aIsFurtherSide) Then ''Both closest points on (1,1,1) side

                ''One of the two extra points is (1,1,1)
                dx_ext0 = dx0 - 1 - 3 * SQUISH_CONSTANT_3D
                dy_ext0 = dy0 - 1 - 3 * SQUISH_CONSTANT_3D
                dz_ext0 = dz0 - 1 - 3 * SQUISH_CONSTANT_3D
                xsv_ext0 = xsb + 1
                ysv_ext0 = ysb + 1
                zsv_ext0 = zsb + 1

                ''Other extra point is based on the shared axis.
                Dim As Byte c = aPoint And bPoint'cast(byte,(aPoint And bPoint))
                if ((c and &h01) <> 0) Then
                    dx_ext1 = dx0 - 2 - 2 * SQUISH_CONSTANT_3D
                    dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_3D
                    dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_3D
                    xsv_ext1 = xsb + 2
                    ysv_ext1 = ysb
                    zsv_ext1 = zsb
                elseif ((c and &h02) <> 0) Then
                    dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_3D
                    dy_ext1 = dy0 - 2 - 2 * SQUISH_CONSTANT_3D
                    dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_3D
                    xsv_ext1 = xsb
                    ysv_ext1 = ysb + 2
                    zsv_ext1 = zsb
                Else
                    dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_3D
                    dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_3D
                    dz_ext1 = dz0 - 2 - 2 * SQUISH_CONSTANT_3D
                    xsv_ext1 = xsb
                    ysv_ext1 = ysb
                    zsv_ext1 = zsb + 2
                EndIf
            Else''Both closest points on (0,0,0) side

                ''One of the two extra points is (0,0,0)
                dx_ext0 = dx0
                dy_ext0 = dy0
                dz_ext0 = dz0
                xsv_ext0 = xsb
                ysv_ext0 = ysb
                zsv_ext0 = zsb

                ''Other extra point is based on the omitted axis.
                Dim As Byte c = aPoint And bPoint'cast(byte,(aPoint or bPoint))
                if ((c and &h01) = 0) Then
                    dx_ext1 = dx0 + 1 - SQUISH_CONSTANT_3D
                    dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_3D
                    dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_3D
                    xsv_ext1 = xsb - 1
                    ysv_ext1 = ysb + 1
                    zsv_ext1 = zsb + 1
                ElseIf ((c and &h02) = 0) then
                    dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_3D
                    dy_ext1 = dy0 + 1 - SQUISH_CONSTANT_3D
                    dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_3D
                    xsv_ext1 = xsb + 1
                    ysv_ext1 = ysb - 1
                    zsv_ext1 = zsb + 1
                Else
                    dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_3D
                    dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_3D
                    dz_ext1 = dz0 + 1 - SQUISH_CONSTANT_3D
                    xsv_ext1 = xsb + 1
                    ysv_ext1 = ysb + 1
                    zsv_ext1 = zsb - 1
                EndIf
            EndIf
        Else ''One point on (0,0,0) side, one point on (1,1,1) side
            Dim As Byte c1, c2
            if (aIsFurtherSide) Then
                c1 = aPoint
                c2 = bPoint
            Else
                c1 = bPoint
                c2 = aPoint
            endif

            ''One contribution is a permutation of (1,1,-1)
            if ((c1 and &h01) = 0) Then
                dx_ext0 = dx0 + 1 - SQUISH_CONSTANT_3D
                dy_ext0 = dy0 - 1 - SQUISH_CONSTANT_3D
                dz_ext0 = dz0 - 1 - SQUISH_CONSTANT_3D
                xsv_ext0 = xsb - 1
                ysv_ext0 = ysb + 1
                zsv_ext0 = zsb + 1
            elseif ((c1 and &h02) = 0) Then
                dx_ext0 = dx0 - 1 - SQUISH_CONSTANT_3D
                dy_ext0 = dy0 + 1 - SQUISH_CONSTANT_3D
                dz_ext0 = dz0 - 1 - SQUISH_CONSTANT_3D
                xsv_ext0 = xsb + 1
                ysv_ext0 = ysb - 1
                zsv_ext0 = zsb + 1
            Else
                dx_ext0 = dx0 - 1 - SQUISH_CONSTANT_3D
                dy_ext0 = dy0 - 1 - SQUISH_CONSTANT_3D
                dz_ext0 = dz0 + 1 - SQUISH_CONSTANT_3D
                xsv_ext0 = xsb + 1
                ysv_ext0 = ysb + 1
                zsv_ext0 = zsb - 1
            endif

            ''One contribution is a permutation of (0,0,2)
            dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_3D
            dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_3D
            dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_3D
            xsv_ext1 = xsb
            ysv_ext1 = ysb
            zsv_ext1 = zsb
            if ((c2 and &h01) <> 0) Then
                dx_ext1 -= 2
                xsv_ext1 += 2
            elseif ((c2 and &h02) <> 0) Then
                dy_ext1 -= 2
                ysv_ext1 += 2
            Else
                dz_ext1 -= 2
                zsv_ext1 += 2
            EndIf
        endif

        ''Contribution (1,0,0)
        Dim As Double dx1 = dx0 - 1 - SQUISH_CONSTANT_3D
        Dim As Double dy1 = dy0 - 0 - SQUISH_CONSTANT_3D
        Dim As Double dz1 = dz0 - 0 - SQUISH_CONSTANT_3D
        Dim As Double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1
        if (attn1 > 0) Then
            attn1 *= attn1
            value += attn1 * attn1 * extrapolate3(xsb + 1, ysb + 0, zsb + 0, dx1, dy1, dz1)
        EndIf

        ''Contribution (0,1,0)
        Dim As Double dx2 = dx0 - 0 - SQUISH_CONSTANT_3D
        Dim As Double dy2 = dy0 - 1 - SQUISH_CONSTANT_3D
        Dim As Double dz2 = dz1
        Dim As Double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2
        if (attn2 > 0) Then
            attn2 *= attn2
            value += attn2 * attn2 * extrapolate3(xsb + 0, ysb + 1, zsb + 0, dx2, dy2, dz2)
        EndIf

        ''Contribution (0,0,1)
        Dim As Double dx3 = dx2
        Dim As Double dy3 = dy1
        Dim As Double dz3 = dz0 - 1 - SQUISH_CONSTANT_3D
        Dim As Double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3
        if (attn3 > 0) Then
            attn3 *= attn3
            value += attn3 * attn3 * extrapolate3(xsb + 0, ysb + 0, zsb + 1, dx3, dy3, dz3)
        EndIf

        ''Contribution (1,1,0)
        Dim As Double dx4 = dx0 - 1 - 2 * SQUISH_CONSTANT_3D
        Dim As Double dy4 = dy0 - 1 - 2 * SQUISH_CONSTANT_3D
        Dim As Double dz4 = dz0 - 0 - 2 * SQUISH_CONSTANT_3D
        Dim As Double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4
        if (attn4 > 0) Then
            attn4 *= attn4
            value += attn4 * attn4 * extrapolate3(xsb + 1, ysb + 1, zsb + 0, dx4, dy4, dz4)
        EndIf

        ''Contribution (1,0,1)
        Dim As Double dx5 = dx4
        Dim As Double dy5 = dy0 - 0 - 2 * SQUISH_CONSTANT_3D
        Dim As Double dz5 = dz0 - 1 - 2 * SQUISH_CONSTANT_3D
        Dim As Double attn5 = 2 - dx5 * dx5 - dy5 * dy5 - dz5 * dz5
        if (attn5 > 0) Then
            attn5 *= attn5
            value += attn5 * attn5 * extrapolate3(xsb + 1, ysb + 0, zsb + 1, dx5, dy5, dz5)
        EndIf

        ''Contribution (0,1,1)
        Dim As Double dx6 = dx0 - 0 - 2 * SQUISH_CONSTANT_3D
        Dim As Double dy6 = dy4
        Dim As Double dz6 = dz5
        Dim As Double attn6 = 2 - dx6 * dx6 - dy6 * dy6 - dz6 * dz6
        if (attn6 > 0) Then
            attn6 *= attn6
            value += attn6 * attn6 * extrapolate3(xsb + 0, ysb + 1, zsb + 1, dx6, dy6, dz6)
        endif
    EndIf

    ''First extra vertex
    Dim As Double attn_ext0 = 2 - dx_ext0 * dx_ext0 - dy_ext0 * dy_ext0 - dz_ext0 * dz_ext0
    if (attn_ext0 > 0) then
        attn_ext0 *= attn_ext0
        value += attn_ext0 * attn_ext0 * extrapolate3(xsv_ext0, ysv_ext0, zsv_ext0, dx_ext0, dy_ext0, dz_ext0)
    EndIf

    ''Second extra vertex
    Dim As Double attn_ext1 = 2 - dx_ext1 * dx_ext1 - dy_ext1 * dy_ext1 - dz_ext1 * dz_ext1
    if (attn_ext1 > 0) Then
        attn_ext1 *= attn_ext1
        value += attn_ext1 * attn_ext1 * extrapolate3(xsv_ext1, ysv_ext1, zsv_ext1, dx_ext1, dy_ext1, dz_ext1)
    EndIf
    value/=NORM_CONSTANT_3D
    return value
End Function

''4D OpenSimplex Noise.
Function OpenSimplexNoise.noise(x As Double ,y As double, z As Double, w As Double) As Double

    ''Place input coordinates on simplectic honeycomb.
    Dim As Double stretchOffset = (x + y + z + w) * STRETCH_CONSTANT_4D
    Dim As Double xs = x + stretchOffset
    Dim As Double ys = y + stretchOffset
    Dim As Double zs = z + stretchOffset
    Dim As Double ws = w + stretchOffset

    ''Floor to get simplectic honeycomb coordinates of rhombo-hypercube super-cell origin.
    Dim As Integer xsb = fastFloor(xs)
    Dim As Integer ysb = fastFloor(ys)
    Dim As Integer zsb = fastFloor(zs)
    Dim As Integer wsb = fastFloor(ws)

    ''Skew out to get actual coordinates of stretched rhombo-hypercube origin. We'll need these later.
    Dim As Double squishOffset = (xsb + ysb + zsb + wsb) * SQUISH_CONSTANT_4D
    Dim As Double xb = xsb + squishOffset
    Dim As Double yb = ysb + squishOffset
    Dim As Double zb = zsb + squishOffset
    Dim As Double wb = wsb + squishOffset

    ''Compute simplectic honeycomb coordinates relative to rhombo-hypercube origin.
    Dim As Double xins = xs - xsb
    Dim As Double yins = ys - ysb
    Dim As Double zins = zs - zsb
    Dim As Double wins = ws - wsb

    ''Sum those together to get a value that determines which region we're in.
    Dim As Double inSum = xins + yins + zins + wins

    ''Positions relative to origin point.
    Dim As Double dx0 = x - xb
    Dim As Double dy0 = y - yb
    Dim As Double dz0 = z - zb
    Dim As Double dw0 = w - wb

    ''We'll be defining these inside the next block and using them afterwards.
    Dim As Double dx_ext0, dy_ext0, dz_ext0, dw_ext0
    Dim As Double dx_ext1, dy_ext1, dz_ext1, dw_ext1
    Dim As Double dx_ext2, dy_ext2, dz_ext2, dw_ext2
    Dim As Integer xsv_ext0, ysv_ext0, zsv_ext0, wsv_ext0
    Dim As Integer xsv_ext1, ysv_ext1, zsv_ext1, wsv_ext1
    Dim As Integer xsv_ext2, ysv_ext2, zsv_ext2, wsv_ext2

    Dim As Double value = 0
    if (inSum <= 1) Then ''We're inside the pentachoron (4-Simplex) at (0,0,0,0)

        ''Determine which two of (0,0,0,1), (0,0,1,0), (0,1,0,0), (1,0,0,0) are closest.
        Dim As Byte aPoint = &h01
        Dim As Double aScore = xins
        Dim As Byte bPoint = &h02
        Dim As Double bScore = yins
        if (aScore >= bScore And zins > bScore) Then
            bScore = zins
            bPoint = &h04
        elseif (aScore < bScore And zins > aScore) Then
            aScore = zins
            aPoint = &h04
        EndIf
        if (aScore >= bScore And wins > bScore) Then
            bScore = wins
            bPoint = &h08
        ElseIf (aScore < bScore And wins > aScore) then
            aScore = wins
            aPoint = &h08
        endif

        ''Now we determine the three lattice points not part of the pentachoron that may contribute.
        ''This depends on the closest two pentachoron vertices, including (0,0,0,0)
        Dim As Double uins = 1 - inSum
        if (uins > aScore Or uins > bScore) Then ''(0,0,0,0) is one of the closest two pentachoron vertices.
            Dim As Byte c = iif(bScore > aScore , bPoint , aPoint) ''Our other closest vertex is the closest out of a and b.
            if ((c and &h01) = 0) Then
                xsv_ext0 = xsb - 1
                xsv_ext1 = xsv_ext2 = xsb
                dx_ext0 = dx0 + 1
                dx_ext1 = dx_ext2 = dx0
            Else
                xsv_ext0 = xsv_ext1 = xsv_ext2 = xsb + 1
                dx_ext0 = dx_ext1 = dx_ext2 = dx0 - 1
            EndIf

            if ((c and &h02) = 0) Then
                ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb
                dy_ext0 = dy_ext1 = dy_ext2 = dy0
                if ((c and &h01) = &h01) Then
                    ysv_ext0 -= 1
                    dy_ext0 += 1
                Else
                    ysv_ext1 -= 1
                    dy_ext1 += 1
                EndIf
            Else
                ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb + 1
                dy_ext0 = dy_ext1 = dy_ext2 = dy0 - 1
            EndIf

            if ((c and &h04) = 0) Then
                zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb
                dz_ext0 = dz_ext1 = dz_ext2 = dz0
                if ((c and &h03) <> 0) Then
                    if ((c and &h03) = &h03) Then
                        zsv_ext0 -= 1
                        dz_ext0 += 1
                    Else
                        zsv_ext1 -= 1
                        dz_ext1 += 1
                    EndIf
                Else
                    zsv_ext2 -= 1
                    dz_ext2 += 1
                EndIf
            Else
                zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb + 1
                dz_ext0 = dz_ext1 = dz_ext2 = dz0 - 1
            EndIf

            if ((c and &h08) = 0) Then
                wsv_ext0 = wsv_ext1 = wsb
                wsv_ext2 = wsb - 1
                dw_ext0 = dw_ext1 = dw0
                dw_ext2 = dw0 + 1
            Else
                wsv_ext0 = wsv_ext1 = wsv_ext2 = wsb + 1
                dw_ext0 = dw_ext1 = dw_ext2 = dw0 - 1
            EndIf
        Else ''(0,0,0,0) is not one of the closest two pentachoron vertices.
            Dim As Byte c = cast(Byte,(aPoint or bPoint)) ''Our three extra vertices are determined by the closest two.

            if ((c and &h01) = 0) Then
                xsv_ext0 = xsv_ext2 = xsb
                xsv_ext1 = xsb - 1
                dx_ext0 = dx0 - 2 * SQUISH_CONSTANT_4D
                dx_ext1 = dx0 + 1 - SQUISH_CONSTANT_4D
                dx_ext2 = dx0 - SQUISH_CONSTANT_4D
            Else
                xsv_ext0 = xsv_ext1 = xsv_ext2 = xsb + 1
                dx_ext0 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
                dx_ext1 = dx_ext2 = dx0 - 1 - SQUISH_CONSTANT_4D
            EndIf

            if ((c and &h02) = 0) Then
                ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb
                dy_ext0 = dy0 - 2 * SQUISH_CONSTANT_4D
                dy_ext1 = dy_ext2 = dy0 - SQUISH_CONSTANT_4D
                if ((c and &h01) = &h01) Then
                    ysv_ext1 -= 1
                    dy_ext1 += 1
                Else
                    ysv_ext2 -= 1
                    dy_ext2 += 1
                EndIf
            Else
                ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb + 1
                dy_ext0 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
                dy_ext1 = dy_ext2 = dy0 - 1 - SQUISH_CONSTANT_4D
            EndIf

            if ((c and &h04) = 0) Then
                zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb
                dz_ext0 = dz0 - 2 * SQUISH_CONSTANT_4D
                dz_ext1 = dz_ext2 = dz0 - SQUISH_CONSTANT_4D
                if ((c and &h03) = &h03) Then
                    zsv_ext1 -= 1
                    dz_ext1 += 1
                Else
                    zsv_ext2 -= 1
                    dz_ext2 += 1
                EndIf
            Else
                zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb + 1
                dz_ext0 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
                dz_ext1 = dz_ext2 = dz0 - 1 - SQUISH_CONSTANT_4D
            EndIf

            if ((c and &h08) = 0) Then
                wsv_ext0 = wsv_ext1 = wsb
                wsv_ext2 = wsb - 1
                dw_ext0 = dw0 - 2 * SQUISH_CONSTANT_4D
                dw_ext1 = dw0 - SQUISH_CONSTANT_4D
                dw_ext2 = dw0 + 1 - SQUISH_CONSTANT_4D
            Else
                wsv_ext0 = wsv_ext1 = wsv_ext2 = wsb + 1
                dw_ext0 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
                dw_ext1 = dw_ext2 = dw0 - 1 - SQUISH_CONSTANT_4D
            EndIf
        endif

        ''Contribution (0,0,0,0)
        Dim As Double attn0 = 2 - dx0 * dx0 - dy0 * dy0 - dz0 * dz0 - dw0 * dw0
        if (attn0 > 0) Then
            attn0 *= attn0
            value += attn0 * attn0 * extrapolate4(xsb + 0, ysb + 0, zsb + 0, wsb + 0, dx0, dy0, dz0, dw0)
        EndIf

        ''Contribution (1,0,0,0)
        Dim As Double dx1 = dx0 - 1 - SQUISH_CONSTANT_4D
        Dim As Double dy1 = dy0 - 0 - SQUISH_CONSTANT_4D
        Dim As Double dz1 = dz0 - 0 - SQUISH_CONSTANT_4D
        Dim As Double dw1 = dw0 - 0 - SQUISH_CONSTANT_4D
        Dim As Double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1 - dw1 * dw1
        if (attn1 > 0) Then
            attn1 *= attn1
            value += attn1 * attn1 * extrapolate4(xsb + 1, ysb + 0, zsb + 0, wsb + 0, dx1, dy1, dz1, dw1)
        EndIf

        ''Contribution (0,1,0,0)
        Dim As Double dx2 = dx0 - 0 - SQUISH_CONSTANT_4D
        Dim As Double dy2 = dy0 - 1 - SQUISH_CONSTANT_4D
        Dim As Double dz2 = dz1
        Dim As Double dw2 = dw1
        Dim As Double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2 - dw2 * dw2
        if (attn2 > 0) Then
            attn2 *= attn2
            value += attn2 * attn2 * extrapolate4(xsb + 0, ysb + 1, zsb + 0, wsb + 0, dx2, dy2, dz2, dw2)
        EndIf

        ''Contribution (0,0,1,0)
        Dim As Double dx3 = dx2
        Dim As Double dy3 = dy1
        Dim As Double dz3 = dz0 - 1 - SQUISH_CONSTANT_4D
        Dim As Double dw3 = dw1
        Dim As Double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3 - dw3 * dw3
        if (attn3 > 0) Then
            attn3 *= attn3
            value += attn3 * attn3 * extrapolate4(xsb + 0, ysb + 0, zsb + 1, wsb + 0, dx3, dy3, dz3, dw3)
        EndIf

        ''Contribution (0,0,0,1)
        Dim As Double dx4 = dx2
        Dim As Double dy4 = dy1
        Dim As Double dz4 = dz1
        Dim As Double dw4 = dw0 - 1 - SQUISH_CONSTANT_4D
        Dim As Double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4 - dw4 * dw4
        if (attn4 > 0) Then
            attn4 *= attn4
            value += attn4 * attn4 * extrapolate4(xsb + 0, ysb + 0, zsb + 0, wsb + 1, dx4, dy4, dz4, dw4)
        EndIf
    Elseif (inSum >= 3) Then ''We're inside the pentachoron (4-Simplex) at (1,1,1,1)
        ''Determine which two of (1,1,1,0), (1,1,0,1), (1,0,1,1), (0,1,1,1) are closest.
        Dim As Byte aPoint = &h0E
        Dim As Double aScore = xins
        Dim As Byte bPoint = &h0D
        Dim As Double bScore = yins
        if (aScore <= bScore And zins < bScore) Then
            bScore = zins
            bPoint = &h0B
        ElseIf (aScore > bScore And zins < aScore) then
            aScore = zins
            aPoint = &h0B
        EndIf
        if (aScore <= bScore And wins < bScore) Then
            bScore = wins
            bPoint = &h07
        ElseIf (aScore > bScore And wins < aScore) then
            aScore = wins
            aPoint = &h07
        EndIf

        ''Now we determine the three lattice points not part of the pentachoron that may contribute.
        ''This depends on the closest two pentachoron vertices, including (0,0,0,0)
        Dim As Double uins = 4 - inSum
        if (uins < aScore Or uins < bScore) Then ''(1,1,1,1) is one of the closest two pentachoron vertices.
            Dim As Byte c = iif(bScore < aScore , bPoint , aPoint) ''Our other closest vertex is the closest out of a and b.

            if ((c and &h01) <> 0) Then
                xsv_ext0 = xsb + 2
                xsv_ext1 = xsv_ext2 = xsb + 1
                dx_ext0 = dx0 - 2 - 4 * SQUISH_CONSTANT_4D
                dx_ext1 = dx_ext2 = dx0 - 1 - 4 * SQUISH_CONSTANT_4D
            Else
                xsv_ext0 = xsv_ext1 = xsv_ext2 = xsb
                dx_ext0 = dx_ext1 = dx_ext2 = dx0 - 4 * SQUISH_CONSTANT_4D
            EndIf

            if ((c and &h02) <> 0) Then
                ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb + 1
                dy_ext0 = dy_ext1 = dy_ext2 = dy0 - 1 - 4 * SQUISH_CONSTANT_4D
                if ((c and &h01) <> 0) Then
                    ysv_ext1 += 1
                    dy_ext1 -= 1
                Else
                    ysv_ext0 += 1
                    dy_ext0 -= 1
                EndIf
            Else
                ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb
                dy_ext0 = dy_ext1 = dy_ext2 = dy0 - 4 * SQUISH_CONSTANT_4D
            EndIf

            if ((c and &h04) <> 0) Then
                zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb + 1
                dz_ext0 = dz_ext1 = dz_ext2 = dz0 - 1 - 4 * SQUISH_CONSTANT_4D
                if ((c and &h03) <> &h03) Then
                    if ((c and &h03) = 0) Then
                        zsv_ext0 += 1
                        dz_ext0 -= 1
                    Else
                        zsv_ext1 += 1
                        dz_ext1 -= 1
                    EndIf
                Else
                    zsv_ext2 += 1
                    dz_ext2 -= 1
                EndIf
            Else
                zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb
                dz_ext0 = dz_ext1 = dz_ext2 = dz0 - 4 * SQUISH_CONSTANT_4D
            EndIf

            if ((c and &h08) <> 0) Then
                wsv_ext0 = wsv_ext1 = wsb + 1
                wsv_ext2 = wsb + 2
                dw_ext0 = dw_ext1 = dw0 - 1 - 4 * SQUISH_CONSTANT_4D
                dw_ext2 = dw0 - 2 - 4 * SQUISH_CONSTANT_4D
            Else
                wsv_ext0 = wsv_ext1 = wsv_ext2 = wsb
                dw_ext0 = dw_ext1 = dw_ext2 = dw0 - 4 * SQUISH_CONSTANT_4D
            EndIf
        Else ''(1,1,1,1) is not one of the closest two pentachoron vertices.
            Dim As Byte c = cast(Byte,(aPoint And bPoint)) ''Our three extra vertices are determined by the closest two.

            if ((c and &h01) <> 0) Then
                xsv_ext0 = xsv_ext2 = xsb + 1
                xsv_ext1 = xsb + 2
                dx_ext0 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
                dx_ext1 = dx0 - 2 - 3 * SQUISH_CONSTANT_4D
                dx_ext2 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D
            Else
                xsv_ext0 = xsv_ext1 = xsv_ext2 = xsb
                dx_ext0 = dx0 - 2 * SQUISH_CONSTANT_4D
                dx_ext1 = dx_ext2 = dx0 - 3 * SQUISH_CONSTANT_4D
            EndIf

            if ((c and &h02) <> 0) Then
                ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb + 1
                dy_ext0 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
                dy_ext1 = dy_ext2 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D
                if ((c and &h01) <> 0) Then
                    ysv_ext2 += 1
                    dy_ext2 -= 1
                Else
                    ysv_ext1 += 1
                    dy_ext1 -= 1
                EndIf
            Else
                ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb
                dy_ext0 = dy0 - 2 * SQUISH_CONSTANT_4D
                dy_ext1 = dy_ext2 = dy0 - 3 * SQUISH_CONSTANT_4D
            EndIf

            if ((c and &h04) <> 0) Then
                zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb + 1
                dz_ext0 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
                dz_ext1 = dz_ext2 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D
                if ((c and &h03) <> 0) Then
                    zsv_ext2 += 1
                    dz_ext2 -= 1
                Else
                    zsv_ext1 += 1
                    dz_ext1 -= 1
                EndIf
            Else
                zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb
                dz_ext0 = dz0 - 2 * SQUISH_CONSTANT_4D
                dz_ext1 = dz_ext2 = dz0 - 3 * SQUISH_CONSTANT_4D
            EndIf

            if ((c and &h08) <> 0) Then
                wsv_ext0 = wsv_ext1 = wsb + 1
                wsv_ext2 = wsb + 2
                dw_ext0 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
                dw_ext1 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D
                dw_ext2 = dw0 - 2 - 3 * SQUISH_CONSTANT_4D
            Else
                wsv_ext0 = wsv_ext1 = wsv_ext2 = wsb
                dw_ext0 = dw0 - 2 * SQUISH_CONSTANT_4D
                dw_ext1 = dw_ext2 = dw0 - 3 * SQUISH_CONSTANT_4D
            EndIf
        endif

        ''Contribution (1,1,1,0)
        Dim As Double dx4 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dy4 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dz4 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dw4 = dw0 - 3 * SQUISH_CONSTANT_4D
        Dim As Double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4 - dw4 * dw4
        if (attn4 > 0) Then
            attn4 *= attn4
            value += attn4 * attn4 * extrapolate4(xsb + 1, ysb + 1, zsb + 1, wsb + 0, dx4, dy4, dz4, dw4)
        EndIf

        ''Contribution (1,1,0,1)
        Dim As Double dx3 = dx4
        Dim As Double dy3 = dy4
        Dim As Double dz3 = dz0 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dw3 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D
        Dim As Double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3 - dw3 * dw3
        if (attn3 > 0) Then
            attn3 *= attn3
            value += attn3 * attn3 * extrapolate4(xsb + 1, ysb + 1, zsb + 0, wsb + 1, dx3, dy3, dz3, dw3)
        EndIf

        ''Contribution (1,0,1,1)
        Dim As Double dx2 = dx4
        Dim As Double dy2 = dy0 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dz2 = dz4
        Dim As Double dw2 = dw3
        Dim As Double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2 - dw2 * dw2
        if (attn2 > 0) Then
            attn2 *= attn2
            value += attn2 * attn2 * extrapolate4(xsb + 1, ysb + 0, zsb + 1, wsb + 1, dx2, dy2, dz2, dw2)
        EndIf

        ''Contribution (0,1,1,1)
        Dim As Double dx1 = dx0 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dz1 = dz4
        Dim As Double dy1 = dy4
        Dim As Double dw1 = dw3
        Dim As Double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1 - dw1 * dw1
        if (attn1 > 0) Then
            attn1 *= attn1
            value += attn1 * attn1 * extrapolate4(xsb + 0, ysb + 1, zsb + 1, wsb + 1, dx1, dy1, dz1, dw1)
        EndIf

        ''Contribution (1,1,1,1)
        dx0 = dx0 - 1 - 4 * SQUISH_CONSTANT_4D
        dy0 = dy0 - 1 - 4 * SQUISH_CONSTANT_4D
        dz0 = dz0 - 1 - 4 * SQUISH_CONSTANT_4D
        dw0 = dw0 - 1 - 4 * SQUISH_CONSTANT_4D
        Dim As Double attn0 = 2 - dx0 * dx0 - dy0 * dy0 - dz0 * dz0 - dw0 * dw0
        if (attn0 > 0) Then
            attn0 *= attn0
            value += attn0 * attn0 * extrapolate4(xsb + 1, ysb + 1, zsb + 1, wsb + 1, dx0, dy0, dz0, dw0)
        EndIf
    ElseIf (inSum <= 2) then ''We're inside the first dispentachoron (Rectified 4-Simplex)
        Dim As Double aScore
        Dim As Byte aPoint
        Dim As boolean aIsBiggerSide = TRUE
        Dim As Double bScore
        Dim As Byte bPoint
        Dim As boolean bIsBiggerSide = TRUE

        ''Decide between (1,1,0,0) and (0,0,1,1)
        if (xins + yins > zins + wins) Then
            aScore = xins + yins
            aPoint = &h03
        Else
            aScore = zins + wins
            aPoint = &h0C
        EndIf

        ''Decide between (1,0,1,0) and (0,1,0,1)
        if (xins + zins > yins + wins) Then
            bScore = xins + zins
            bPoint = &h05
        Else
            bScore = yins + wins
            bPoint = &h0A
        EndIf

        ''Closer between (1,0,0,1) and (0,1,1,0) will replace the further of a and b, if closer.
        if (xins + wins > yins + zins) Then
            Dim As Double score = xins + wins
            if (aScore >= bScore And score > bScore) Then
                bScore = score
                bPoint = &h09
            ElseIf (aScore < bScore And score > aScore) then
                aScore = score
                aPoint = &h09
            EndIf
        Else
            Dim As Double score = yins + zins
            if (aScore >= bScore And score > bScore) Then
                bScore = score
                bPoint = &h06
            ElseIf (aScore < bScore And score > aScore) then
                aScore = score
                aPoint = &h06
            EndIf
        EndIf

        ''Decide if (1,0,0,0) is closer.
        Dim As Double p1 = 2 - inSum + xins
        if (aScore >= bScore And p1 > bScore) Then
            bScore = p1
            bPoint = &h01
            bIsBiggerSide = FALSE
        ElseIf (aScore < bScore And p1 > aScore) then
            aScore = p1
            aPoint = &h01
            aIsBiggerSide = FALSE
        EndIf

        ''Decide if (0,1,0,0) is closer.
        Dim As Double p2 = 2 - inSum + yins
        if (aScore >= bScore And p2 > bScore) Then
            bScore = p2
            bPoint = &h02
            bIsBiggerSide = FALSE
        ElseIf (aScore < bScore And p2 > aScore) Then
            aScore = p2
            aPoint = &h02
            aIsBiggerSide = FALSE
        EndIf

        ''Decide if (0,0,1,0) is closer.
        Dim As Double p3 = 2 - inSum + zins
        if (aScore >= bScore And p3 > bScore) Then
            bScore = p3
            bPoint = &h04
            bIsBiggerSide = FALSE
        elseif (aScore < bScore And p3 > aScore) Then
            aScore = p3
            aPoint = &h04
            aIsBiggerSide = FALSE
        EndIf

        ''Decide if (0,0,0,1) is closer.
        Dim As Double p4 = 2 - inSum + wins
        if (aScore >= bScore And p4 > bScore) Then
            bScore = p4
            bPoint = &h08
            bIsBiggerSide = FALSE
        ElseIf (aScore < bScore And p4 > aScore) then
            aScore = p4
            aPoint = &h08
            aIsBiggerSide = FALSE
        endif

        ''Where each of the two closest points are determines how the extra three vertices are calculated.
        if (aIsBiggerSide = bIsBiggerSide) Then
            if (aIsBiggerSide) then ''Both closest points on the bigger side
                Dim As Byte c1 = Cast(Byte,(aPoint or bPoint))
                Dim As Byte c2 = cast(Byte,(aPoint And bPoint))
                if ((c1 and &h01) = 0) Then
                    xsv_ext0 = xsb
                    xsv_ext1 = xsb - 1
                    dx_ext0 = dx0 - 3 * SQUISH_CONSTANT_4D
                    dx_ext1 = dx0 + 1 - 2 * SQUISH_CONSTANT_4D
                Else
                    xsv_ext0 = xsv_ext1 = xsb + 1
                    dx_ext0 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D
                    dx_ext1 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
                EndIf

                if ((c1 and &h02) = 0) Then
                    ysv_ext0 = ysb
                    ysv_ext1 = ysb - 1
                    dy_ext0 = dy0 - 3 * SQUISH_CONSTANT_4D
                    dy_ext1 = dy0 + 1 - 2 * SQUISH_CONSTANT_4D
                Else
                    ysv_ext0 = ysv_ext1 = ysb + 1
                    dy_ext0 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D
                    dy_ext1 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
                endif

                if ((c1 and &h04) = 0) Then
                    zsv_ext0 = zsb
                    zsv_ext1 = zsb - 1
                    dz_ext0 = dz0 - 3 * SQUISH_CONSTANT_4D
                    dz_ext1 = dz0 + 1 - 2 * SQUISH_CONSTANT_4D
                Else
                    zsv_ext0 = zsv_ext1 = zsb + 1
                    dz_ext0 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D
                    dz_ext1 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
                EndIf

                if ((c1 and &h08) = 0) Then
                    wsv_ext0 = wsb
                    wsv_ext1 = wsb - 1
                    dw_ext0 = dw0 - 3 * SQUISH_CONSTANT_4D
                    dw_ext1 = dw0 + 1 - 2 * SQUISH_CONSTANT_4D
                Else
                    wsv_ext0 = wsv_ext1 = wsb + 1
                    dw_ext0 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D
                    dw_ext1 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
                endif

                ''One combination is a permutation of (0,0,0,2) based on c2
                xsv_ext2 = xsb
                ysv_ext2 = ysb
                zsv_ext2 = zsb
                wsv_ext2 = wsb
                dx_ext2 = dx0 - 2 * SQUISH_CONSTANT_4D
                dy_ext2 = dy0 - 2 * SQUISH_CONSTANT_4D
                dz_ext2 = dz0 - 2 * SQUISH_CONSTANT_4D
                dw_ext2 = dw0 - 2 * SQUISH_CONSTANT_4D
                if ((c2 and &h01) <> 0) Then
                    xsv_ext2 += 2
                    dx_ext2 -= 2
                ElseIf ((c2 and &h02) <> 0) Then
                    ysv_ext2 += 2
                    dy_ext2 -= 2
                ElseIf ((c2 and &h04) <> 0) then
                    zsv_ext2 += 2
                    dz_ext2 -= 2
                Else
                    wsv_ext2 += 2
                    dw_ext2 -= 2
                endif

            Else ''Both closest points on the smaller side
                ''One of the two extra points is (0,0,0,0)
                xsv_ext2 = xsb
                ysv_ext2 = ysb
                zsv_ext2 = zsb
                wsv_ext2 = wsb
                dx_ext2 = dx0
                dy_ext2 = dy0
                dz_ext2 = dz0
                dw_ext2 = dw0

                ''Other two points are based on the omitted axes.
                Dim As Byte c = cast(Byte,(aPoint or bPoint))

                if ((c and &h01) = 0) Then
                    xsv_ext0 = xsb - 1
                    xsv_ext1 = xsb
                    dx_ext0 = dx0 + 1 - SQUISH_CONSTANT_4D
                    dx_ext1 = dx0 - SQUISH_CONSTANT_4D
                Else
                    xsv_ext0 = xsv_ext1 = xsb + 1
                    dx_ext0 = dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_4D
                EndIf

                if ((c and &h02) = 0) Then
                    ysv_ext0 = ysv_ext1 = ysb
                    dy_ext0 = dy_ext1 = dy0 - SQUISH_CONSTANT_4D
                    if ((c and &h01) = &h01) Then
                        ysv_ext0 -= 1
                        dy_ext0 += 1
                    Else
                        ysv_ext1 -= 1
                        dy_ext1 += 1
                    EndIf
                Else
                    ysv_ext0 = ysv_ext1 = ysb + 1
                    dy_ext0 = dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_4D
                EndIf

                if ((c and &h04) = 0) Then
                    zsv_ext0 = zsv_ext1 = zsb
                    dz_ext0 = dz_ext1 = dz0 - SQUISH_CONSTANT_4D
                    if ((c and &h03) = &h03) Then
                        zsv_ext0 -= 1
                        dz_ext0 += 1
                    Else
                        zsv_ext1 -= 1
                        dz_ext1 += 1
                    EndIf
                Else
                    zsv_ext0 = zsv_ext1 = zsb + 1
                    dz_ext0 = dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_4D
                EndIf

                if ((c and &h08) = 0) Then
                    wsv_ext0 = wsb
                    wsv_ext1 = wsb - 1
                    dw_ext0 = dw0 - SQUISH_CONSTANT_4D
                    dw_ext1 = dw0 + 1 - SQUISH_CONSTANT_4D
                Else
                    wsv_ext0 = wsv_ext1 = wsb + 1
                    dw_ext0 = dw_ext1 = dw0 - 1 - SQUISH_CONSTANT_4D
                EndIf

            EndIf
        Else ''One point on each "side"
            Dim As Byte c1, c2
            if (aIsBiggerSide) Then
                c1 = aPoint
                c2 = bPoint
            Else
                c1 = bPoint
                c2 = aPoint
            EndIf

            ''Two contributions are the bigger-sided point with each 0 replaced with -1.
            if ((c1 and &h01) = 0) Then
                xsv_ext0 = xsb - 1
                xsv_ext1 = xsb
                dx_ext0 = dx0 + 1 - SQUISH_CONSTANT_4D
                dx_ext1 = dx0 - SQUISH_CONSTANT_4D
            Else
                xsv_ext0 = xsv_ext1 = xsb + 1
                dx_ext0 = dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_4D
            EndIf

            if ((c1 and &h02) = 0) Then
                ysv_ext0 = ysv_ext1 = ysb
                dy_ext0 = dy_ext1 = dy0 - SQUISH_CONSTANT_4D
                if ((c1 and &h01) = &h01) Then
                    ysv_ext0 -= 1
                    dy_ext0 += 1
                Else
                    ysv_ext1 -= 1
                    dy_ext1 += 1
                EndIf
            Else
                ysv_ext0 = ysv_ext1 = ysb + 1
                dy_ext0 = dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_4D
            EndIf

            if ((c1 and &h04) = 0) Then
                zsv_ext0 = zsv_ext1 = zsb
                dz_ext0 = dz_ext1 = dz0 - SQUISH_CONSTANT_4D
                if ((c1 and &h03) = &h03) Then
                    zsv_ext0 -= 1
                    dz_ext0 += 1
                Else
                    zsv_ext1 -= 1
                    dz_ext1 += 1
                EndIf
            Else
                zsv_ext0 = zsv_ext1 = zsb + 1
                dz_ext0 = dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_4D
            EndIf

            if ((c1 and &h08) = 0) Then
                wsv_ext0 = wsb
                wsv_ext1 = wsb - 1
                dw_ext0 = dw0 - SQUISH_CONSTANT_4D
                dw_ext1 = dw0 + 1 - SQUISH_CONSTANT_4D
            Else
                wsv_ext0 = wsv_ext1 = wsb + 1
                dw_ext0 = dw_ext1 = dw0 - 1 - SQUISH_CONSTANT_4D
            EndIf

            ''One contribution is a permutation of (0,0,0,2) based on the smaller-sided point
            xsv_ext2 = xsb
            ysv_ext2 = ysb
            zsv_ext2 = zsb
            wsv_ext2 = wsb
            dx_ext2 = dx0 - 2 * SQUISH_CONSTANT_4D
            dy_ext2 = dy0 - 2 * SQUISH_CONSTANT_4D
            dz_ext2 = dz0 - 2 * SQUISH_CONSTANT_4D
            dw_ext2 = dw0 - 2 * SQUISH_CONSTANT_4D
            if ((c2 and &h01) <> 0) Then
                xsv_ext2 += 2
                dx_ext2 -= 2
            ElseIf ((c2 and &h02) <> 0) Then
                ysv_ext2 += 2
                dy_ext2 -= 2
            elseif ((c2 and &h04) <> 0) Then
                zsv_ext2 += 2
                dz_ext2 -= 2
            Else
                wsv_ext2 += 2
                dw_ext2 -= 2
            EndIf
        EndIf

        ''Contribution (1,0,0,0)
        Dim As Double dx1 = dx0 - 1 - SQUISH_CONSTANT_4D
        Dim As Double dy1 = dy0 - 0 - SQUISH_CONSTANT_4D
        Dim As Double dz1 = dz0 - 0 - SQUISH_CONSTANT_4D
        Dim As Double dw1 = dw0 - 0 - SQUISH_CONSTANT_4D
        Dim As Double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1 - dw1 * dw1
        if (attn1 > 0) Then
            attn1 *= attn1
            value += attn1 * attn1 * extrapolate4(xsb + 1, ysb + 0, zsb + 0, wsb + 0, dx1, dy1, dz1, dw1)
        EndIf

        ''Contribution (0,1,0,0)
        Dim As Double dx2 = dx0 - 0 - SQUISH_CONSTANT_4D
        Dim As Double dy2 = dy0 - 1 - SQUISH_CONSTANT_4D
        Dim As Double dz2 = dz1
        Dim As Double dw2 = dw1
        Dim As Double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2 - dw2 * dw2
        if (attn2 > 0) Then
            attn2 *= attn2
            value += attn2 * attn2 * extrapolate4(xsb + 0, ysb + 1, zsb + 0, wsb + 0, dx2, dy2, dz2, dw2)
        EndIf

        ''Contribution (0,0,1,0)
        Dim As Double dx3 = dx2
        Dim As Double dy3 = dy1
        Dim As Double dz3 = dz0 - 1 - SQUISH_CONSTANT_4D
        Dim As Double dw3 = dw1
        Dim As Double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3 - dw3 * dw3
        if (attn3 > 0) Then
            attn3 *= attn3
            value += attn3 * attn3 * extrapolate4(xsb + 0, ysb + 0, zsb + 1, wsb + 0, dx3, dy3, dz3, dw3)
        EndIf

        ''Contribution (0,0,0,1)
        Dim As Double dx4 = dx2
        Dim As Double dy4 = dy1
        Dim As Double dz4 = dz1
        Dim As Double dw4 = dw0 - 1 - SQUISH_CONSTANT_4D
        Dim As Double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4 - dw4 * dw4
        if (attn4 > 0) Then
            attn4 *= attn4
            value += attn4 * attn4 * extrapolate4(xsb + 0, ysb + 0, zsb + 0, wsb + 1, dx4, dy4, dz4, dw4)
        EndIf

        ''Contribution (1,1,0,0)
        Dim As Double dx5 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy5 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz5 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw5 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn5 = 2 - dx5 * dx5 - dy5 * dy5 - dz5 * dz5 - dw5 * dw5
        if (attn5 > 0) Then
            attn5 *= attn5
            value += attn5 * attn5 * extrapolate4(xsb + 1, ysb + 1, zsb + 0, wsb + 0, dx5, dy5, dz5, dw5)
        EndIf

        ''Contribution (1,0,1,0)
        Dim As Double dx6 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy6 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz6 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw6 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn6 = 2 - dx6 * dx6 - dy6 * dy6 - dz6 * dz6 - dw6 * dw6
        if (attn6 > 0) Then
            attn6 *= attn6
            value += attn6 * attn6 * extrapolate4(xsb + 1, ysb + 0, zsb + 1, wsb + 0, dx6, dy6, dz6, dw6)
        EndIf

        ''Contribution (1,0,0,1)
        Dim As Double dx7 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy7 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz7 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw7 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn7 = 2 - dx7 * dx7 - dy7 * dy7 - dz7 * dz7 - dw7 * dw7
        if (attn7 > 0) Then
            attn7 *= attn7
            value += attn7 * attn7 * extrapolate4(xsb + 1, ysb + 0, zsb + 0, wsb + 1, dx7, dy7, dz7, dw7)
        EndIf

        ''Contribution (0,1,1,0)
        Dim As Double dx8 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy8 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz8 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw8 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn8 = 2 - dx8 * dx8 - dy8 * dy8 - dz8 * dz8 - dw8 * dw8
        if (attn8 > 0) Then
            attn8 *= attn8
            value += attn8 * attn8 * extrapolate4(xsb + 0, ysb + 1, zsb + 1, wsb + 0, dx8, dy8, dz8, dw8)
        EndIf

        ''Contribution (0,1,0,1)
        Dim As Double dx9 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy9 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz9 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw9 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn9 = 2 - dx9 * dx9 - dy9 * dy9 - dz9 * dz9 - dw9 * dw9
        if (attn9 > 0) Then
            attn9 *= attn9
            value += attn9 * attn9 * extrapolate4(xsb + 0, ysb + 1, zsb + 0, wsb + 1, dx9, dy9, dz9, dw9)
        EndIf

        ''Contribution (0,0,1,1)
        Dim As Double dx10 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy10 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz10 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw10 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn10 = 2 - dx10 * dx10 - dy10 * dy10 - dz10 * dz10 - dw10 * dw10
        if (attn10 > 0) Then
            attn10 *= attn10
            value += attn10 * attn10 * extrapolate4(xsb + 0, ysb + 0, zsb + 1, wsb + 1, dx10, dy10, dz10, dw10)
        EndIf
    Else ''We're inside the second dispentachoron (Rectified 4-Simplex)
        Dim As Double aScore
        Dim As Byte aPoint
        Dim As boolean aIsBiggerSide = TRUE
        Dim As Double bScore
        Dim As Byte bPoint
        Dim As boolean bIsBiggerSide = TRUE

        ''Decide between (0,0,1,1) and (1,1,0,0)
        if (xins + yins < zins + wins) Then
            aScore = xins + yins
            aPoint = &h0C
        Else
            aScore = zins + wins
            aPoint = &h03
        EndIf

        ''Decide between (0,1,0,1) and (1,0,1,0)
        if (xins + zins < yins + wins) Then
            bScore = xins + zins
            bPoint = &h0A
        Else
            bScore = yins + wins
            bPoint = &h05
        EndIf

        ''Closer between (0,1,1,0) and (1,0,0,1) will replace the further of a and b, if closer.
        if (xins + wins < yins + zins) Then
            Dim As Double score = xins + wins
            if (aScore <= bScore And score < bScore) Then
                bScore = score
                bPoint = &h06
            ElseIf (aScore > bScore And score < aScore) Then
                aScore = score
                aPoint = &h06
            EndIf
        Else
            Dim As Double score = yins + zins
            if (aScore <= bScore And score < bScore) Then
                bScore = score
                bPoint = &h09
            elseif (aScore > bScore And score < aScore) Then
                aScore = score
                aPoint = &h09
            EndIf
        EndIf

        ''Decide if (0,1,1,1) is closer.
        Dim As Double p1 = 3 - inSum + xins
        if (aScore <= bScore And p1 < bScore) Then
            bScore = p1
            bPoint = &h0E
            bIsBiggerSide = FALSE
        ElseIf (aScore > bScore And p1 < aScore) Then
            aScore = p1
            aPoint = &h0E
            aIsBiggerSide = FALSE
        EndIf

        ''Decide if (1,0,1,1) is closer.
        Dim As Double p2 = 3 - inSum + yins
        if (aScore <= bScore And p2 < bScore) Then
            bScore = p2
            bPoint = &h0D
            bIsBiggerSide = FALSE
        ElseIf (aScore > bScore And p2 < aScore) Then
            aScore = p2
            aPoint = &h0D
            aIsBiggerSide = FALSE
        EndIf

        ''Decide if (1,1,0,1) is closer.
        Dim As Double p3 = 3 - inSum + zins
        if (aScore <= bScore And p3 < bScore) Then
            bScore = p3
            bPoint = &h0B
            bIsBiggerSide = FALSE
        ElseIf (aScore > bScore And p3 < aScore) Then
            aScore = p3
            aPoint = &h0B
            aIsBiggerSide = FALSE
        EndIf

        ''Decide if (1,1,1,0) is closer.
        Dim As Double p4 = 3 - inSum + wins
        if (aScore <= bScore And p4 < bScore) Then
            bScore = p4
            bPoint = &h07
            bIsBiggerSide = FALSE
        elseif (aScore > bScore and p4 < aScore) Then
            aScore = p4
            aPoint = &h07
            aIsBiggerSide = FALSE
        EndIf

        ''Where each of the two closest points are determines how the extra three vertices are calculated.
        if (aIsBiggerSide = bIsBiggerSide) Then
            if (aIsBiggerSide) Then ''Both closest points on the bigger side
                Dim As Byte c1 = Cast(Byte,(aPoint And bPoint))
                Dim As Byte c2 = cast(Byte,(aPoint or bPoint))

                ''Two contributions are permutations of (0,0,0,1) and (0,0,0,2) based on c1
                xsv_ext0 = xsv_ext1 = xsb
                ysv_ext0 = ysv_ext1 = ysb
                zsv_ext0 = zsv_ext1 = zsb
                wsv_ext0 = wsv_ext1 = wsb
                dx_ext0 = dx0 - SQUISH_CONSTANT_4D
                dy_ext0 = dy0 - SQUISH_CONSTANT_4D
                dz_ext0 = dz0 - SQUISH_CONSTANT_4D
                dw_ext0 = dw0 - SQUISH_CONSTANT_4D
                dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_4D
                dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_4D
                dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_4D
                dw_ext1 = dw0 - 2 * SQUISH_CONSTANT_4D
                if ((c1 and &h01) <> 0) Then
                    xsv_ext0 += 1
                    dx_ext0 -= 1
                    xsv_ext1 += 2
                    dx_ext1 -= 2
                ElseIf ((c1 and &h02) <> 0) Then
                    ysv_ext0 += 1
                    dy_ext0 -= 1
                    ysv_ext1 += 2
                    dy_ext1 -= 2
                ElseIf ((c1 and &h04) <> 0) Then
                    zsv_ext0 += 1
                    dz_ext0 -= 1
                    zsv_ext1 += 2
                    dz_ext1 -= 2
                Else
                    wsv_ext0 += 1
                    dw_ext0 -= 1
                    wsv_ext1 += 2
                    dw_ext1 -= 2
                EndIf

                ''One contribution is a permutation of (1,1,1,-1) based on c2
                xsv_ext2 = xsb + 1
                ysv_ext2 = ysb + 1
                zsv_ext2 = zsb + 1
                wsv_ext2 = wsb + 1
                dx_ext2 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
                dy_ext2 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
                dz_ext2 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
                dw_ext2 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
                if ((c2 and &h01) = 0) Then
                    xsv_ext2 -= 2
                    dx_ext2 += 2
                ElseIf ((c2 and &h02) = 0) Then
                    ysv_ext2 -= 2
                    dy_ext2 += 2
                ElseIf ((c2 and &h04) = 0) Then
                    zsv_ext2 -= 2
                    dz_ext2 += 2
                Else
                    wsv_ext2 -= 2
                    dw_ext2 += 2
                EndIf
            Else ''Both closest points on the smaller side
                ''One of the two extra points is (1,1,1,1)
                xsv_ext2 = xsb + 1
                ysv_ext2 = ysb + 1
                zsv_ext2 = zsb + 1
                wsv_ext2 = wsb + 1
                dx_ext2 = dx0 - 1 - 4 * SQUISH_CONSTANT_4D
                dy_ext2 = dy0 - 1 - 4 * SQUISH_CONSTANT_4D
                dz_ext2 = dz0 - 1 - 4 * SQUISH_CONSTANT_4D
                dw_ext2 = dw0 - 1 - 4 * SQUISH_CONSTANT_4D

                ''Other two points are based on the shared axes.
                Dim As Byte c = cast(Byte,(aPoint And bPoint))

                if ((c and &h01) <> 0) Then
                    xsv_ext0 = xsb + 2
                    xsv_ext1 = xsb + 1
                    dx_ext0 = dx0 - 2 - 3 * SQUISH_CONSTANT_4D
                    dx_ext1 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D
                Else
                    xsv_ext0 = xsv_ext1 = xsb
                    dx_ext0 = dx_ext1 = dx0 - 3 * SQUISH_CONSTANT_4D
                EndIf

                if ((c and &h02) <> 0) Then
                    ysv_ext0 = ysv_ext1 = ysb + 1
                    dy_ext0 = dy_ext1 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D
                    if ((c and &h01) = 0) Then
                        ysv_ext0 += 1
                        dy_ext0 -= 1
                    Else
                        ysv_ext1 += 1
                        dy_ext1 -= 1
                    EndIf
                Else
                    ysv_ext0 = ysv_ext1 = ysb
                    dy_ext0 = dy_ext1 = dy0 - 3 * SQUISH_CONSTANT_4D
                EndIf

                if ((c and &h04) <> 0) Then
                    zsv_ext0 = zsv_ext1 = zsb + 1
                    dz_ext0 = dz_ext1 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D
                    if ((c and &h03) = 0) Then
                        zsv_ext0 += 1
                        dz_ext0 -= 1
                    Else
                        zsv_ext1 += 1
                        dz_ext1 -= 1
                    EndIf
                Else
                    zsv_ext0 = zsv_ext1 = zsb
                    dz_ext0 = dz_ext1 = dz0 - 3 * SQUISH_CONSTANT_4D
                EndIf

                if ((c and &h08) <> 0) Then
                    wsv_ext0 = wsb + 1
                    wsv_ext1 = wsb + 2
                    dw_ext0 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D
                    dw_ext1 = dw0 - 2 - 3 * SQUISH_CONSTANT_4D
                Else
                    wsv_ext0 = wsv_ext1 = wsb
                    dw_ext0 = dw_ext1 = dw0 - 3 * SQUISH_CONSTANT_4D
                EndIf
            EndIf
        Else ''One point on each "side"
            Dim As Byte c1, c2
            if (aIsBiggerSide) Then
                c1 = aPoint
                c2 = bPoint
            Else
                c1 = bPoint
                c2 = aPoint
            EndIf

            ''Two contributions are the bigger-sided point with each 1 replaced with 2.
            if ((c1 and &h01) <> 0) Then
                xsv_ext0 = xsb + 2
                xsv_ext1 = xsb + 1
                dx_ext0 = dx0 - 2 - 3 * SQUISH_CONSTANT_4D
                dx_ext1 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D
            Else
                xsv_ext0 = xsv_ext1 = xsb
                dx_ext0 = dx_ext1 = dx0 - 3 * SQUISH_CONSTANT_4D
            EndIf

            if ((c1 and &h02) <> 0) Then
                ysv_ext0 = ysv_ext1 = ysb + 1
                dy_ext0 = dy_ext1 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D
                if ((c1 and &h01) = 0) Then
                    ysv_ext0 += 1
                    dy_ext0 -= 1
                Else
                    ysv_ext1 += 1
                    dy_ext1 -= 1
                EndIf
            Else
                ysv_ext0 = ysv_ext1 = ysb
                dy_ext0 = dy_ext1 = dy0 - 3 * SQUISH_CONSTANT_4D
            EndIf

            if ((c1 and &h04) <> 0) Then
                zsv_ext0 = zsv_ext1 = zsb + 1
                dz_ext0 = dz_ext1 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D
                if ((c1 and &h03) = 0) Then
                    zsv_ext0 += 1
                    dz_ext0 -= 1
                Else
                    zsv_ext1 += 1
                    dz_ext1 -= 1
                EndIf
            Else
                zsv_ext0 = zsv_ext1 = zsb
                dz_ext0 = dz_ext1 = dz0 - 3 * SQUISH_CONSTANT_4D
            EndIf

            if ((c1 and &h08) <> 0) Then
                wsv_ext0 = wsb + 1
                wsv_ext1 = wsb + 2
                dw_ext0 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D
                dw_ext1 = dw0 - 2 - 3 * SQUISH_CONSTANT_4D
            Else
                wsv_ext0 = wsv_ext1 = wsb
                dw_ext0 = dw_ext1 = dw0 - 3 * SQUISH_CONSTANT_4D
            EndIf

            ''One contribution is a permutation of (1,1,1,-1) based on the smaller-sided point
            xsv_ext2 = xsb + 1
            ysv_ext2 = ysb + 1
            zsv_ext2 = zsb + 1
            wsv_ext2 = wsb + 1
            dx_ext2 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
            dy_ext2 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
            dz_ext2 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
            dw_ext2 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
            if ((c2 and &h01) = 0) Then
                xsv_ext2 -= 2
                dx_ext2 += 2
            ElseIf ((c2 and &h02) = 0) Then
                ysv_ext2 -= 2
                dy_ext2 += 2
            ElseIf ((c2 And &h04) = 0) Then
                zsv_ext2 -= 2
                dz_ext2 += 2
            else
                wsv_ext2 -= 2
                dw_ext2 += 2
            EndIf
        EndIf

        ''Contribution (1,1,1,0)
        Dim As Double dx4 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dy4 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dz4 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dw4 = dw0 - 3 * SQUISH_CONSTANT_4D
        Dim As Double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4 - dw4 * dw4
        if (attn4 > 0) Then
            attn4 *= attn4
            value += attn4 * attn4 * extrapolate4(xsb + 1, ysb + 1, zsb + 1, wsb + 0, dx4, dy4, dz4, dw4)
        EndIf

        ''Contribution (1,1,0,1)
        Dim As Double dx3 = dx4
        Dim As Double dy3 = dy4
        Dim As Double dz3 = dz0 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dw3 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D
        Dim As Double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3 - dw3 * dw3
        if (attn3 > 0) Then
            attn3 *= attn3
            value += attn3 * attn3 * extrapolate4(xsb + 1, ysb + 1, zsb + 0, wsb + 1, dx3, dy3, dz3, dw3)
        EndIf

        ''Contribution (1,0,1,1)
        Dim As Double dx2 = dx4
        Dim As Double dy2 = dy0 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dz2 = dz4
        Dim As Double dw2 = dw3
        Dim As Double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2 - dw2 * dw2
        if (attn2 > 0) Then
            attn2 *= attn2
            value += attn2 * attn2 * extrapolate4(xsb + 1, ysb + 0, zsb + 1, wsb + 1, dx2, dy2, dz2, dw2)
        EndIf

        ''Contribution (0,1,1,1)
        Dim As Double dx1 = dx0 - 3 * SQUISH_CONSTANT_4D
        Dim As Double dz1 = dz4
        Dim As Double dy1 = dy4
        Dim As Double dw1 = dw3
        Dim As Double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1 - dw1 * dw1
        if (attn1 > 0) Then
            attn1 *= attn1
            value += attn1 * attn1 * extrapolate4(xsb + 0, ysb + 1, zsb + 1, wsb + 1, dx1, dy1, dz1, dw1)
        EndIf

        ''Contribution (1,1,0,0)
        Dim As Double dx5 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy5 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz5 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw5 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn5 = 2 - dx5 * dx5 - dy5 * dy5 - dz5 * dz5 - dw5 * dw5
        if (attn5 > 0) Then
            attn5 *= attn5
            value += attn5 * attn5 * extrapolate4(xsb + 1, ysb + 1, zsb + 0, wsb + 0, dx5, dy5, dz5, dw5)
        EndIf

        ''Contribution (1,0,1,0)
        Dim As Double dx6 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy6 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz6 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw6 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn6 = 2 - dx6 * dx6 - dy6 * dy6 - dz6 * dz6 - dw6 * dw6
        if (attn6 > 0) Then
            attn6 *= attn6
            value += attn6 * attn6 * extrapolate4(xsb + 1, ysb + 0, zsb + 1, wsb + 0, dx6, dy6, dz6, dw6)
        EndIf

        ''Contribution (1,0,0,1)
        Dim As Double dx7 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy7 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz7 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw7 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn7 = 2 - dx7 * dx7 - dy7 * dy7 - dz7 * dz7 - dw7 * dw7
        if (attn7 > 0) Then
            attn7 *= attn7
            value += attn7 * attn7 * extrapolate4(xsb + 1, ysb + 0, zsb + 0, wsb + 1, dx7, dy7, dz7, dw7)
        EndIf

        ''Contribution (0,1,1,0)
        Dim As Double dx8 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy8 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz8 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw8 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn8 = 2 - dx8 * dx8 - dy8 * dy8 - dz8 * dz8 - dw8 * dw8
        if (attn8 > 0) Then
            attn8 *= attn8
            value += attn8 * attn8 * extrapolate4(xsb + 0, ysb + 1, zsb + 1, wsb + 0, dx8, dy8, dz8, dw8)
        EndIf

        ''Contribution (0,1,0,1)
        Dim As Double dx9 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy9 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz9 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw9 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn9 = 2 - dx9 * dx9 - dy9 * dy9 - dz9 * dz9 - dw9 * dw9
        if (attn9 > 0) Then
            attn9 *= attn9
            value += attn9 * attn9 * extrapolate4(xsb + 0, ysb + 1, zsb + 0, wsb + 1, dx9, dy9, dz9, dw9)
        EndIf

        ''Contribution (0,0,1,1)
        Dim As Double dx10 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dy10 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dz10 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double dw10 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D
        Dim As Double attn10 = 2 - dx10 * dx10 - dy10 * dy10 - dz10 * dz10 - dw10 * dw10
        if (attn10 > 0) Then
            attn10 *= attn10
            value += attn10 * attn10 * extrapolate4(xsb + 0, ysb + 0, zsb + 1, wsb + 1, dx10, dy10, dz10, dw10)
        EndIf
    EndIf

    ''First extra vertex
    Dim As Double attn_ext0 = 2 - dx_ext0 * dx_ext0 - dy_ext0 * dy_ext0 - dz_ext0 * dz_ext0 - dw_ext0 * dw_ext0
    if (attn_ext0 > 0) then
        attn_ext0 *= attn_ext0
        value += attn_ext0 * attn_ext0 * extrapolate4(xsv_ext0, ysv_ext0, zsv_ext0, wsv_ext0, dx_ext0, dy_ext0, dz_ext0, dw_ext0)
    EndIf

    ''Second extra vertex
    Dim As Double attn_ext1 = 2 - dx_ext1 * dx_ext1 - dy_ext1 * dy_ext1 - dz_ext1 * dz_ext1 - dw_ext1 * dw_ext1
    if (attn_ext1 > 0) Then
        attn_ext1 *= attn_ext1
        value += attn_ext1 * attn_ext1 * extrapolate4(xsv_ext1, ysv_ext1, zsv_ext1, wsv_ext1, dx_ext1, dy_ext1, dz_ext1, dw_ext1)
    EndIf

    ''Third extra vertex
    Dim As Double attn_ext2 = 2 - dx_ext2 * dx_ext2 - dy_ext2 * dy_ext2 - dz_ext2 * dz_ext2 - dw_ext2 * dw_ext2
    if (attn_ext2 > 0) Then
        attn_ext2 *= attn_ext2
        value += attn_ext2 * attn_ext2 * extrapolate4(xsv_ext2, ysv_ext2, zsv_ext2, wsv_ext2, dx_ext2, dy_ext2, dz_ext2, dw_ext2)
    EndIf
    value/=NORM_CONSTANT_4D
    return value
End Function