I have adapted that for better 3d lines - may help.
Function Line3d( mesh, x0#,z0#,x1#,z1#, y# , r, g, b) If mesh = 0 mesh = CreateMesh() surf = CreateSurface(mesh) Else surf = GetSurface(mesh,1) If CountVertices(surf)>30000 surf = CreateSurface(mesh) EndIf End If dx# = x1 - x0 dz# = z1 - z0 d# = Sqr( dx*dx + dz*dz ) * 4.0 dx = dx / d dz = dz / d v0 = AddVertex( surf , x0-dz, z0+dx , y ) v1 = AddVertex( surf, x1-dz, z1 + dx, y ) v2 = AddVertex( surf, x1+dz, z1 - dx, y ) v3 = AddVertex( surf, x0 + dz, z0 - dx , y ) For v = v0 To v3 VertexColor surf, v, r,g, b Next AddTriangle surf,v0,v1,v2 AddTriangle surf,v2,v3,v0 entityfx mesh,2 Return mesh End Function