Hi!


patches in which four points (along one edge) are all the same point.

The rendering can be seen here:
	http://i.imgur.com/eq2UIXR.png

As you can see, there is a visible unwanted artifact in the corner of 
each patch. The two patches shown are essentially the same, except with 



Expected rendering is a smooth surface without the artifact.

Below is the code used to render the above example.

Thanks
Timwi




#version 3.7;

global_settings { assumed_gamma 1.0 }

camera {
     location <45, 31, -10>
     look_at <40, 21, 200>
     right x*image_width/image_height
}

light_source {
     <660, 300, -525>
     color rgb 1
}

// Example 1: First point in each row is the same point
bicubic_patch {
     type 1 flatness 0.001
     u_steps 4 v_steps 4
     <32.2168, -23.78125, 0>, <34.4968, -23.78125, 0>, <35.2168, 
-23.78125, -0.72>, <35.2168, -23.78125, -3>,
     <32.2168, -23.78125, 0>, <34.4968, -22.10256, 0>, <35.2168, 
-21.57244, -0.72>, <35.2168, -21.57244, -3>,
     <32.2168, -23.78125, 0>, <33.9709, -21.55577, 0>, <34.52483, 
-20.85299, -0.72>, <34.52483, -20.85299, -3>,
     <32.2168, -23.78125, 0>, <32.30556, -21.50298, 0>, <32.33359, 
-20.78352, -0.72>, <32.33359, -20.78352, -3>
     rotate 180*x

     scale 1.4
     translate <-5, 0, 0>
     pigment { color <1, 0, 0> }
}

// Example 2: First row is all the same point
bicubic_patch {
     type 1 flatness 0.001
     u_steps 4 v_steps 4
     <32.2168, -23.78125, 0>, <32.2168, -23.78125, 0>, <32.2168, 
-23.78125, 0>, <32.2168, -23.78125, 0>,
     <34.4968, -23.78125, 0>, <34.4968, -22.10256, 0>, <33.9709, 
-21.55577, 0>, <32.30556, -21.50298, 0>,
     <35.2168, -23.78125, -0.72>, <35.2168, -21.57244, -0.72>, 
<34.52483, -20.85299, -0.72>, <32.33359, -20.78352, -0.72>,
     <35.2168, -23.78125, -3>, <35.2168, -21.57244, -3>, <34.52483, 
-20.85299, -3>, <32.33359, -20.78352, -3>
     rotate 180*x

     scale 1.4
     pigment { color <1, 1, 0> }
}

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