Generate mesh with collision

-- Test

function ENT:MakeCube(pos,ang,length,width,height)
    pos=pos or Vector()
    length=length or 1
    width=width or 1
    height=height or 1

    -- http://wiki.unity3d.com/index.php/ProceduralPrimitives
    local p0 = Vector(-length*0.5,-width*0.5,height*0.5)+pos
    local p1 = Vector(length*0.5,-width*0.5,height*0.5)+pos
    local p2 = Vector(length*0.5,-width*0.5,-height*0.5)+pos
    local p3 = Vector(-length*0.5,-width*0.5,-height*0.5)+pos
    p0:Rotate(ang)
    p1:Rotate(ang)
    p2:Rotate(ang)
    p3:Rotate(ang)

    local p4 = Vector(-length*0.5,width*0.5,height*0.5)+pos
    local p5 = Vector(length*0.5,width*0.5,height*0.5)+pos
    local p6 = Vector(length*0.5,width*0.5,-height*0.5)+pos
    local p7 = Vector(-length*0.5,width*0.5,-height*0.5)+pos
    p4:Rotate(ang)
    p5:Rotate(ang)
    p6:Rotate(ang)
    p7:Rotate(ang)

    local vertices = {
        -- Left
        p0, p1, p2,
        p2, p3, p0,

        -- Back
        p7, p4, p0,
        p7, p0, p3,

        -- Top
        p4, p5, p1,
        p4, p1, p0,

        -- Bottom
        p3, p6, p7,
        p3, p2, p6,

        -- Front
        p5, p6, p2,
        p5, p2, p1,

        -- Right
        p6, p5, p7,
        p5, p4, p7,
    };

    local up = Vector(0,0,1)
    local down = Vector(0,0,-1)
    local front = Vector(1,0,0)
    local back = Vector(-1,0,0)
    local left = Vector(0,-1,0)
    local right = Vector(0,1,0)

    local normales = {
        -- Left
        left, left, left, left, left, left,

        -- Back
        back, back, back, back, back, back,

        -- Top
        up, up, up, up, up, up,

        -- Bottom
        down, down, down, down, down, down,

        -- Front
        front, front, front, front, front, front,

        -- Right
        right, right, right, right, right, right,
    };

    local _00 = {0,0}
    local _10 = {1,0}
    local _01 = {0,1}
    local _11 = {1,1}

    local uvs = {
        -- Left
        _10, _00, _01, _01, _11, _10,

        -- Back
        _11, _10, _00, _11, _00, _01,

        -- Top
        _00, _01, _11, _00, _11, _10,

        -- Bottom
        _00, _11, _10, _00, _01, _11,

        -- Front
        _00, _01, _11, _00, _11, _10,

        -- Right
        _01, _00, _11, _00, _10, _11,
    }

    local verts = {}
    for i=1,6*6 do
        table.insert(verts,{pos = vertices[i], normal = normales[i], u = uvs[i][1], v = uvs[i][2] })
    end

    return verts,vertices
end

ENT:AddHook("Initialize","test",function(self)
    local width=500
    local height=1000
    local size=100
    self:SetRenderMode(RENDERMODE_TRANSALPHA)
    self:SetColor(Color(255,255,255,1))

    local sections={
        {self:MakeCube(Vector(0,-width/2,height/2),Angle(0,0,0),size,size,height)},
        {self:MakeCube(Vector(0,0,height+(size/2)),Angle(0,0,0),size,width+size,size)},
        {self:MakeCube(Vector(0,width/2,height/2),Angle(0,0,0),size,size,height)},
    }
    if CLIENT then
        self:SetRenderBounds(Vector(0,-(width/2)-(size/2),0),Vector(0,(width/2)+(size/2),height))
        self.meshes = {}
        for k,v in pairs(sections) do
            local newmesh=Mesh()
            newmesh:BuildFromTriangles(v[1])
            table.insert(self.meshes,newmesh)
        end
    end
    local meshes={}
    for k,v in pairs(sections) do
        table.insert(meshes,v[2])
    end
    self:PhysicsInitMultiConvex(meshes)
    self:EnableCustomCollisions(true)

    self.phys = self:GetPhysicsObject()
    if not IsValid(self.phys) then
        self:Remove()
        return
    end

    self.phys:SetMass(5000)
    self.phys:Wake()
end)

local rendermat=Material("models/props_wasteland/wood_fence01a")

ENT:AddHook("Draw","test",function(self)
    self:DrawModel()

    mat = Matrix()
    mat:Translate( self:GetPos() )
    mat:Rotate(self:GetAngles())
    mat:Scale( Vector( 1, 1, 1 ) )


    render.SetMaterial(rendermat)
    cam.PushModelMatrix(mat)
        for k,v in pairs(self.meshes) do
            v:Draw()
        end
    cam.PopModelMatrix()
end)

-- https://facepunch.com/showthread.php?t=1459677
ENT:AddHook("Think","test",function(self)
    if CLIENT and IsValid(self.phys) then
        self.phys:EnableMotion(false)
        self.phys:SetPos(self:GetPos())
        self.phys:SetAngles(self:GetAngles())
    end
end)