local segments
local numCorners

local bWidth = 1
local bTexCoord = 1
local bColor = Color(255,255,255,255)

function render.StartBeam3D(corners)

    numCorners = math.max(corners or 3,3)

    segments = {}
end

function render.AddBeam3D(pos,width,texCoord,color)

    segments[#segments+1] = {pos=pos,width=width or bWidth,texCoord=texCoord or bTexCoord,color=color or bColor}
end

function render.EndBeam3D()

    local rings = {}

    for i=1,#segments-1 do

        local pos = segments[i].pos
        local nextPos = segments[i+1].pos

        local dir = (nextPos-pos):GetNormal()

        rings[i] = {}

        for j=1,numCorners do

            local p = dir:Angle()

            p:RotateAroundAxis(p:Forward(),360*j/numCorners)

            p = pos+p:Right()*segments[i].width

            rings[i][j] = p
        end

        debugoverlay.Line(pos,nextPos,RealFrameTime())
    end

    mesh.Begin(MATERIAL_QUADS,#segments*numCorners)

    for i=1,#segments-2 do

        local ring = rings[i]
        local nextRing = rings[i+1]

        local t = segments[i+1].texCoord

        for j=1,numCorners-1 do

            local c = segments[i].color
            local c2 = segments[i+1].color

            local p = ring[j]
            local p2 = ring[j+1]
            local p3 = nextRing[j+1]
            local p4 = nextRing[j]

            local norm = (p2-p):Cross(p3-p):GetNormal()

            mesh.Position(p4)
            mesh.Normal(norm)
            mesh.Color(c2.r,c2.g,c2.b,c2.a)
            mesh.TexCoord(0,0,0)
            mesh.AdvanceVertex()

            mesh.Position(p3)
            mesh.Normal(norm)
            mesh.Color(c2.r,c2.g,c2.b,c2.a)
            mesh.TexCoord(0,1,0)
            mesh.AdvanceVertex()

            mesh.Position(p2)
            mesh.Normal(norm)
            mesh.Color(c.r,c.g,c.b,c.a)
            mesh.TexCoord(0,1,t)
            mesh.AdvanceVertex()

            mesh.Position(p)
            mesh.Normal(norm)
            mesh.Color(c.r,c.g,c.b,c.a)
            mesh.TexCoord(0,0,t)
            mesh.AdvanceVertex()

            debugoverlay.Line(p,p2,RealFrameTime())
            debugoverlay.Line(p2,p3,RealFrameTime())
            debugoverlay.Line(p,p4,RealFrameTime())
        end

        local c = segments[i].color
        local c2 = segments[i+1].color

        local p = ring[numCorners]
        local p2 = ring[1]
        local p3 = nextRing[1]
        local p4 = nextRing[numCorners]

        local norm = (p2-p):Cross(p3-p):GetNormal()

        mesh.Position(p4)
        mesh.Normal(norm)
        mesh.Color(c2.r,c2.g,c2.b,c2.a)
        mesh.TexCoord(0,0,0)
        mesh.AdvanceVertex()

        mesh.Position(p3)
        mesh.Normal(norm)
        mesh.Color(c2.r,c2.g,c2.b,c2.a)
        mesh.TexCoord(0,1,0)
        mesh.AdvanceVertex()

        mesh.Position(p2)
        mesh.Normal(norm)
        mesh.Color(c.r,c.g,c.b,c.a)
        mesh.TexCoord(0,1,t)
        mesh.AdvanceVertex()

        mesh.Position(p)
        mesh.Normal(norm)
        mesh.Color(c.r,c.g,c.b,c.a)
        mesh.TexCoord(0,0,t)
        mesh.AdvanceVertex()

        debugoverlay.Line(p,p2,RealFrameTime())
        debugoverlay.Line(p2,p3,RealFrameTime())
        debugoverlay.Line(p,p4,RealFrameTime())
    end

    mesh.End()

    segments = nil
    numCorners = nil
end