"Bald Eagle" <cre### [at] netscapenet> wrote:
> OK, so I managed to noodle out the 8 different possible "straightforward" square
> control point matrices - starting out from one of 4 corners and beginning the
> definition of the patch in either the X or Z direction.
>
> These were rendered with the default counter-clockwise uv-vectors, as pairs of
> front and back faces of the patches.
>
> Then a second set of patches were rendered with the uv-vectors running
> clockwise.
>
> It's still not clear exactly how the uv-vectors and the control points map to
> each other, but I have noticed that you can pick out mirrored sets of matrices -
> so that might be a good lead to pursue tomorrow.
>
> I'm posting this here now for interested folks to look over, ponder, and
> hopefully make some helpful observations and suggestions.
>
> Thanks

#version 3.7;

#include "functions.inc"
global_settings {
    assumed_gamma 1.000000
    max_trace_level 3
    charset utf8
}
sky_sphere {
    pigment {rgb<0.051, 0.051, 0.051>}
}

#declare Default_texture = texture{pigment {rgb 0.8}}

#declare Material_001 = texture{
    pigment{uv_mapping image_map{"/home/leonid/UV_bicubic.png" gamma 1.1000
interpolate 2 filter all 0.0000 transmit all 0.0000}
        translate <0.0000,0.0000,0.0000>
        rotate <0.0000,0.0000,0.0000>
        scale <1.0000,-1.0000,1.0000>  // WARNING! SCALE Y NEGATIVE!
        }
    finish{
        diffuse 0.8000
        brilliance 1.8000
          }
}
#declare data_SurfPatch_ob =
bicubic_patch {    type 1 u_steps 5 v_steps 5
 uv_vectors <0.0000,0.0000> <1.0000,0.0000> <1.0000,1.0000> <0.0000,1.0000>
<-1.5000,-1.5000,0.0000> <-1.5000,-0.5000,0.0000> <-1.5000,0.5000,0.0000>
<-1.5000,1.5000,0.0000> <-0.5000,-1.5000,0.0000> <-0.5000,-0.5000,0.0000>
<-0.5000,0.5000,0.0000> <-0.5000,1.5000,0.0000> <0.5000,-1.5000,0.0000>
<0.5000,-0.5000,0.0000> <0.5000,0.5000,0.0000> <0.5000,1.5000,0.0000>
<1.5000,-1.5000,0.0000> <1.5000,-0.5000,0.0000> <1.5000,0.5000,0.0000>
<1.5000,1.5000,0.0000>    texture{Material_001}
}
object {data_SurfPatch_ob
    matrix <1.000000, 0.000000, 0.000000,  0.000000, -0.000000, -1.000000,
0.000000, 1.000000, -0.000000,  0.000000, 0.000000, 0.000000>
}

light_source {
    <4.08,5.9,-1.01>
    color rgb<1, 1, 1>
    fade_distance 29.9999828339
    fade_power 1
}
camera {
    perspective
    location  <0,0,0>
    look_at  <0,0,-1>
    right <-1.7777777777777777, 0, 0>
    up <0, 1, 0>
    angle  49.134343
    rotate  <-27.098163, 46.688390, -0.903519>
    translate <7.481132, 5.343666, 6.507640>
}

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