Faceting in Glossy Reflections

[Dariusz Makowski (Dadal)]

Ah wow ok now I can see it... Funny I never noticed it before... I guess its because I work with 5-100mil polygon models huh...

Nice one thanks ! Will see if I can figure out some work around it heh...

[max@mfx]

Yep, more polys and subdivs definitely helps to lessen the problems. Unfortunately we are stuck with triangulated converted CAD geometry, no subdivs or smoothing works on that...

[Dariusz Makowski (Dadal)]

Doh ur geometry must be very low Ours is just fine... no fisible tesselation issues.

I was thinking maybe applying a bump with neutral normal map texture would work ? Will have to five it a go might do something...weird.

[max@mfx]

The geometry is not that bad, pretty standard for product viz. The problem is that it is triangulated and not hand built. Makes it very hard to edit and tweak.

Bump mapping only makes it worse!

[Morbid Angel]

can you show us what geo is causing the issue for you?
By the way I checked this in mental ray and I could not reproduce it, but that's not to say that mr does not cheat it some other way...I remember seeing this issue on a amb occlusion pass in mr once, so I think its a general issue with low tesselated surfaces.

[max@mfx]

As I said, it's a default Maya poly sphere. The actual geometry we use is not important here, as I have reproduced it in a very simple scene. But generally our converted geometry is much better than the sphere in the example. The artifacts still shows up in certain cases though, like in shallow viewing angles, presumable where the rays intersect the same geometry because of the shallow reflection angle.

[Dariusz Makowski (Dadal)]

Have you tried interpolation maybe?

I should probably try it myself but I'm too busy atm

[max@mfx]

I have tried that and a lot more, nothing as of now seems to help unfortunately...

[vlado]

Unfortunately I have no solution for you other than to increase the surface tessellation or use subdivision surfaces, or use a different BRDF. It's an issue that happens to various degrees in all renderers that've checked.

Best regards,
Vlado

[max@mfx]

Ok, that is frustrating...

Would be a killer if you could invent something to make it work!

[vlado]

You can try the Cook-Torrance BRDF, it tends to work somewhat better for this case...

Best regards,
Vlado

[max@mfx]

Thanks, will possibly give that a try. But I guess that involves coding a custom shader?

[vlado]

But I guess that involves coding a custom shader?

Nope; if you are using nightly builds, go to V-Ray > Create > Create from V-Ray Plugin > Material > BRDFCookTorrance. It doesn't have a nice UI (yet), but it might help.

Best regards,
Vlado

[max@mfx]

Cool, we are using 2.20 stable though... It may be worth going nightly here.

[vlado]

It might be already in 2.20, it was added quite a while ago.

Best regards,
Vlado