
TEXTURE COORDINATE SYSTEM
=========================

'u' means horizontal offset / position
'v' means vertical offset / position (Z axis)

bottom texture: bu, bv fields in brush sides
top    texture: tu, tv fields in brush sides
(usually placed in every side, but if only in a single side
then the texture is axis aligned and 1:1 scale)

also: tscale in brush top, bscale in brush bottom

side texture: u1 and/or uscale in brush sides
              v1 and/or vscale in brush sides

new coord kind: za = height, specifies absolute Z anchor coordinate
(i.e. for top of the texture).
can be used with or without v1 or vscale.
default is top of brush, or bottom if no top, otherwise 0.

