Hmmm.

I have 4 bicubic patches arranged in a square.
I want to texture them all as a single unit, but they all seem to get textured
independently, so I get 4 copies of my uv-map.

I have them in a union, with the uv texture applied after that, and merge didn't
work either.

They're all coded the same, and I was thinking about it and thought that maybe
since all 4 had uv_mapping in their separate definitions, that there was where
the problem lay.

So I commented that out in 2 of the patches, and now I get 2 patches with
"elevation lines" - (Yay! If that's what I wanted, but I don't not _now_ )
either I'm doing something wrong, or I'm a step or 2 away from getting right and
can't tell which yet.

Maybe it's got to do with the uv_vectors section, or I need a whole 'nother
array of vectors for the uv mapping?

Another issue I've noticed is that I have to rotate the texture around y by 180
deg when I view it in the usual +z direction.  Is that an inherent property of
the bicubic patch object, or can it be redefined....?

I will post complete scene file once I get more of this worked out.

-----------------------------------------

#declare RedPatch = bicubic_patch {
 type 1 flatness 0.001
 u_steps 4 v_steps 4
 uv_vectors
 <0, 0> <1, 0> <1, 1> <0, 1>
 R11, R12, R13, R14
 R21, R22, R23, R24
 R31, R32, R33, R34
 R41, R42, R43, R44
 //uv_mapping
 #if (UVtex = false)
 texture {
  pigment {
   checker
   color rgbf <1, 1, 1, 0.5>
   color rgbf <1, 0, 0, 0.7>
   scale 1/3
  }
 finish {phong 0.6 phong_size 20}
 }
 #end
 no_shadow
}

---------------------------------

#union {
object {BluePatch}
object {RedPatch}
object {GreenPatch}
object {YellowPatch}
#if (UVtex = true)
 #switch (UVMAP)
 #case (0)
   texture { pigment { image_map { png "Numbered_Grid-Red-Green.png" } scale 2}
rotate y*180}
   #break

...... other cases, and #ends.

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