Alain Martel <kua### [at] videotronca> wrote:
>
> There is a simple explanation for the bicubic_patch : That object only
> have a surface, it have zero thickness.
> The same will happen with the triangle primitive.
>
> Even if you have an union of them forming a completely closed shape,
> they'll never have an interior.
>

While testing a bicubic_patch model vs. the mesh2 Bunny, the first problem that
occurred was that the bicubic_patch version could not accept an inside_vector
(which the mesh2 can, and is required for the media to appear.) I initially
thought that was the primary reason for the patch model not showing up. So I
tried the trick of making an intersection of it with a box, to somehow
'solidify' it; but that did not work either.

My understanding of mesh/mesh2 objects and bicubic_patch objects is that they
are *both* just zero-thickness 'shells' -- so I still don't quite understand why
one works as an object pattern, while the other does not. I still have the
thought that it is due to a missing inside_vector(?). OR, the problem could be
due to the particular bicubic model I used. It is just a union of patches, but
is not a completely 'closed' one. (I made that model many years ago in an *old*
app called sPatch, and it renders OK as-is in POV-ray as a typical object... but
perhaps it has some kind of problem when I try to use it for the object
pattern.)

I should probably try a well-constructed bicubic_patch model from some other
source, to see if it works.

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