On 5/23/19 2:30 PM, Norbert Kern wrote:
> William F Pokorny <ano### [at] anonymousorg> wrote:
>>
...
> 
> Since you are asking directly - my problems were solved after this special IRTC
> round by deleting small normals at the normal section - what else....
> No, it wasn't that easy, but anyway...
> 
> Since then I deleted small normals, when black spots occured. Of course I'm
> curious of the root cause, but my focus is more on the result...
> But here I'm curious...
> 

If the normals are so small at the scene scale they cannot be seen, it 
makes sense compute resource wise to remove them no matter. In a strange 
way, seeing the black artifacts was an indication texture normals too 
small existed and we no longer have this in v38.

Still, I think POV-Ray should handle/filter such normals as people 
sometimes are using a texture/material others coded and it shouldn't 
completely break when used at a different scale(1).

I don't myself know what changed in the code post v37. Maybe something 
got fixed with the static code analysis Christoph runs and reviews now 
and again. I don't remember a specific commit for such an issue, but my 
memory is less good these days. I too might have been busy with real 
life when the change happened.

It is possible to do a binary search of commit versions to localized the 
commit(s) which fixed the issue for your scene. I've done this sort of 
work especially for performance issues. However, it's a very time 
consuming process always. A process worse on *nix systems like mine 
where we must work around sequences of commits in the history which 
don't compile. I have no plans to look for what got fixed - given it 
looks to be fixed.

That said, if you see black spot artifacts due normals in a recent v38 
release, a sample scene would be appreciated.

Bill P.

(1) Drifting... With published materials/textures I think it would be 
helpful to later users to know the original scale where the texture was 
developed and applied. "M_RustyIron12. Applied at 1x scale to objects in 
a 100x,100y,100z range centered at the origin. Camera distance to object 
with texture was roughly 350." Other stuff? Suppose most of us assume 
development in a -1,1 box at the origin and normal-ish camera set up 
after which we fish around for what looks good.

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