Re: [Mesa3d-dev] bug in sphere normal

[Stephen T. <ste...@sf...>]

Brian Paul <br...@va...> writes:

> 
> How do they compare when you enable smooth shading for the sphere?
> 

Oddly, they look the same when smooth shaded. Why?? Then, it's not the
problem of the normal?


> It may be that because of the vertex order for the triangle strips
> being different, that a different provoking vertex is being used
> for filling each facet.

Can that be fixed?

> 
> The GLU spec doesn't say exactly how the triangle (or quad) strips
> are to be oriented in gluSphere so this might be an allowable
> variation.

Variation? But this is a huge visible discrepancy, though. I draw the
box in the light source position. It seems that the specular
reflection is more "accurate" in sgi glu. I can't say for sure though.


> Thanks.  My plan is to replace Mesa's GLU with the SI GLU someday
> (when I find time).

You mean SGI open-source reference implementation? Their code style is
horrible because of over-optimization. Honestly, I like Mesa code much
better. It is more readable.


- Stephen