Johannes Hubert wrote:
> 
> David Greaves wrote in message <36138CC4.6E8891E4@telekinesys.co.uk>...
> 
> >The top picture has the problem.
> >How can I see the floor of the bowl?
> >There should be *no* light illuminating this surface at all!!
> 
> Not really. Only if the texture has an ambient value of 0.0 in its finish
> (which the silver texture doesn't, I assume), wouldn't you see anything. See
> "ambient" in the docs.
> 
> About the strange shadow/reflection: I don't know...
> 
> Johannes.

This sounds a lot like the problem mentioned in my earlier posting 
"Re: Tranlucency and bicubic patches".

In my sample code, I specifically made the ambient 0.0, and there
was no reflection value given (I assume the default is reflection 0?).
I tried to keep it as simple as possible, to eliminate the most likely 
sources of wierdness:

#declare myPatch = bicubic_patch {
   type 1 
   flatness 0.01 
   u_steps 3
   v_steps 3
     <0, 3,  1.0> <1, 2.5,  1.0> <2, 2.5,  1.0> <3, 3,  1.0>
     <0, 2, -0.5> <1, 2.0, -0.5> <2, 2.0, -0.5> <3, 2, -0.5>
     <0, 1,  0.0> <1, 1.0,  1.0> <2, 1.0,  1.0> <3, 1,  1.0>
     <0, 0,  2.0> <1, 0.5,  2.0> <2, 0.5,  2.0> <3, 0,  2.0> 
  translate <-1.5, -1.5, 0>
  texture {
     pigment {color red 1 filter 0}
     finish  {phong 1 phong_size 100 ambient 0 diffuse 0.9}
     }
   }

use a single light_source, just above the mid point between the camera 
and patch object, and have a look at it from several angles.

Lights and shadows are visible on the "wrong" sides of bicubic patches,
it seems, in both Mac and Win versions. Other things like clipped
objects
and discs don't display this feature/bug.

-jr-

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