In article <37b9012b@news.povray.org>, Nieminen Mika <war### [at] cctutfi> wrote:
>Philip Bartol <phi### [at] concentricnet> wrote:
>: The problem is that I found that while the texture had open spaces, the solid
> 
>: parts of the texture only where on the surface of my test object. I figured 
>: that since the pigment goes through the object if you cut it, that using a 
>: transparent color would show the solid portions thorugh the object.
>
>  This is a common misunderstanding among beginners.
>  Povray doesn't handle solid objects, only surfaces. (The keyword 'hollow'
>has _nothing_ to do with this.) Povray handles mathematical surfaces, which
>are infinitely thin.
>  Think about it: Povray calculates the intersection between the viewing ray
>and the object (eg. a sphere). Ok, now it has the coordinates in space for
>the intersection point. Now what? It calculates the color of that point for
>that specific object. It finds that it's transparent. What should it do?
>It traces another ray from there. This ray hits the sphere again at the
>other side. The result is that we see a hollow sphere.
>  Calculating the intersection between the viewing ray and a texture pattern
>in space is quite difficult. Media does this, and you can try doing something
>with it, but expect _slow_ rendering times and not-so-good results.

I'll macro out a union of boxes and clip them to the shape I want before 
messing with Media for a solid grill...

I just didn't figure that the pigment (which the manual describes as solid 
through the object) is only calculated on the surfaces, but it does make 
sence. Someone should re-phrase that portion of the documentation.

For my purposes I can go with a very thin object, as I had said, so that it 
appears solid through. I don't plan on rendering any scenes so close to that 
surface that the detail will be needed...

Thanks

PHIL

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