subdiv approx crashing mental ray with overlapping vertices

[James Deschenes]

I'm having issues with mental ray crashing, both the internal Maya 2010 & 2011 releases, and the standalone 3.7.53 release.

The situation is awfully specific, but it is unfortunately going to be a fairly common scenario for me in the near future.

The situation is that I have meshes that have some split components on them, so they may contain vertices that share the same location.

The meshes also require subdivision approximation. In my case I am using view dependent fine spatial approximation, and I have the CC-mesh export disabled (this is another constraint I have currently)

Last and not least, I have a shading network which has a sampler info facing ratio attribute connected into the v-coord of a ramp.

Whenever I have a situation with all three of these scenarios, mental ray crashes hard (no error, just an illegal operation on my windows box, and an exit on the Linux machines)

My meshes are triangulated on mi-export so I should not have any funky n-gons. I am currently doing some tests to see if switching over to using the CC-mesh can alleviate my issues, and it works in my internal-mayatomr renders, but I'm still having trouble with my standalone renders.

In any case, I'm wondering if anyone has any help or advice. I have attached a Maya 2011 / 2010 and a MI scene which should cause a crash.

[steve]

Hi James,

The situation is that I have meshes that have some split components on them, so they may contain vertices that share the same location.
The meshes also require subdivision approximation. In my case I am using view dependent fine spatial approximation, and I have the CC-mesh export disabled (this is another constraint I have currently)

Last and not least, I have a shading network which has a sampler info facing ratio attribute connected into the v-coord of a ramp.

we have tested your scene example, and it works as expected for us when using ccmesh export. Nowadays, this is the preferred method of rendering subdivision meshes with mental ray. The original hierarchical subdivision surface handling is still supported but is lacking some features. I would like to understand, what is preventing you from using ccmesh ?

Best, Steve.

[James Deschenes]

Hey Steve,

Thanks for the reply. The reason for the use of the old hierarchical subdivision method was because of our own in-house geometry exporter; which does not have ccmesh support implemented. We were wondering if we could get around this issue without having to do any new development, but it looks like it would be best just to implement ccmesh and be done with the issue.

Thanks again for the response!