Given a plane and a 3D point, transform the 3D point to a 2D coordinate along the plane.

I got it.

It's much more complex than just transforming points. It all has to do with which way a mapper will most likely consider "up" and want the texture to point.

Have you ever had a routine you wrote, and have no idea how you got it wo work, except just by going on hunches and looking for patterns, until suddenly it works perfectly? This was almost up there with CSG.

Take a look at this crazy-ass code:

Function TextureCoords(x#,y#,z#,nx#,ny#,nz#)
If nz<0.0
	nx=-nx
	ny=-ny
	nz=-nz
	EndIf
If Abs(nx#)<0.0000001 And Abs(nz#)<0.0000001
	texturev=z/64.0
	textureu=x/64.0*Sgn(ny)
	Return
	EndIf
If Abs(nx#)<0.0000001 And Abs(ny#)<0.0000001
	texturev=y/64.0
	textureu=x/64.0*-Sgn(nz)
	Return
	EndIf
If Abs(nz#)<0.0000001 And Abs(ny#)<0.0000001
	texturev=y/64.0
	textureu=z/64.0*Sgn(nx)
	Return
	EndIf
If Abs(nx)>Abs(nz)
	If Abs(ny)>Abs(nx) roll#=-90.0*Sgn(nx)
	EndIf
If Abs(nx)<Abs(nz)
	If Abs(ny)>Abs(nz)
		If ny>0.0
			If nz>0.0 roll#=180.0
			EndIf
		If ny<0.0
			If nz<0.0 roll#=180.0
			EndIf
		EndIf
	EndIf
If Abs(nx)>Abs(nz) And Abs(ny)>Abs(nz) nz=0
If Abs(nx)>Abs(ny) And Abs(nz)>Abs(ny) ny=0
If Abs(ny)>Abs(nx) And Abs(nz)>Abs(nx) nx=0
dx#=nx#
dy#=ny#
dz#=nz#
dist#=Sqr#((dx#^2)+(dz#^2))
pitch#=ATan2((dy#),dist#)
yaw#=ATan2(dx#,-dz#)
matrix=createtransmatrix(x,y,z)
matrix2=createrotmatrix3(pitch,yaw,roll)
matrix3=mulmatrices(matrix,matrix2)
textureu#=getmatrixelement(matrix3,4,1)/64.0
texturev#=getmatrixelement(matrix3,4,2)/64.0
FreeBank matrix
FreeBank matrix2
FreeBank matrix3
Return