Glossies WAY different with different AA methodss

[davision]

I was playing around with a velvet material (due to a post by n6 here) and came across something I don't understand. I have a simple plane with glossy reflections in a scene with nothign else. I have an HDRI in Vray's Refl/Refr override slot.

When I render with QMC AA (2,4) I get a decent render, but with Adaptive AA of 1,2 I get a metallic material. The reflections are substantially different. Why is this?

QMC Render



AA Render

[davision]

I don't know if this matters, but for my test, I'm not using any global illumination. Just direct lighting with a bunch of vray lights.

[themaxxer]

I have the same problem.

have a look: http://www.chaosgroup.com/forum/phpB...998&highlight=

best regards
themaxxer

[vlado]

The correct render is probably the one with adaptive subdivision AA. The issue is because of the color clamping and/or color mapping when you use the adaptive QMC sampler. If you want to use the Adaptive QMC AA, you'll have to add more subdivisions to the glossy reflections.

The problem is because color mapping/clamping is applied on a sub-pixel, rather than per-pixel level. While this solves some issues with antialiasing of very bright objects, it introduces problems like the one you are having. In recent builds, there is an option to choose between sub-pixel and per-pixel color mapping/clamping.

Best regards,
Vlado