MR hates my model
 

I did a model of a T-rex using a NURBS to Poly to SubD technique. I made sure that I had NO 5 sided faces. The model is made up of 4 and 3 sided faces. It renders fine with Mayas software renderer but Mental Ray won't touch it. I know the problem has to do with the triangles in my poly model. Once I convert the model to SubD and switch to subdivision level 0 I can see that many of the faces seem disconnected from the rest. I ran a simple test. I took a poly cube and converted it to subD then rendered it with Mental Ray. Everything worked as expected. Next, I took a poly cube and spit one of the faces so that it was now 2 triangles. I converted it to SubD then examined it at subD level O. Just like with my T-rex model, the SubD cube had disconnected faces on the side where I split the quad into 2 triangles. The triangles are causing the problem. When I would try to render a subD that was made by converting a poly with triangles, Mental ray would cause Maya to generate this error: "non-quadrilateral face in base mesh not supported."

Question: Is there anything I can do about this besides trying to find every single triangle in my poly T-rex and eliminating them?

I have tried to use Quadrangulate but it didn't help. I don't want to use a dense poly model for my project but if I can't get the subD to render in Mental Ray then I'm going to have to.

By the way, Here is a link to my site incase you want to see the T-rex that is causing me all this trouble. Morphic Motion

Maybe quadchecker will help you out. Check this thread.

It is possible not to have to work out the triangles.


Subdiv Surfaces > Collapse Hierarchy
this will give you higher mesh. BUT you can keep your triangle count down in renders, buy lowering the Tessellation, sample count of 2 should get you close to the original count.

There will be a Higher mesh to deal with. could slow down interactivity for animation. But this is something that would be done right before renders anyway.

Nitroliq, I will check out the link that you provided. Thanks

Pony, Your solution did the trick!! I am so freakin happy:p I will have to read through some of my books to see just exactly what collapsing the hierarchy did but for right now, I'm just thrilled that it worked.

Thanks again..

Well, everything seemed good until I tried to apply a map to the model. First I applied it to the subD model before collapsing the hierarchy but after the collapse, the map was messed up. I guess because of the UV mapping created when doing the collapse. then I tried to create a simple camera view projection UV map from the collapsed model but that pretty much froze up my computer every time I tried.

Unless someone has a better idea, I'm just going to do this:
1 low poly model
2. convert to subd
3 convert subd back to poly using adaptive setting
4 create my UV maps from converted model
5 right before rendering, I'll apply poly smooth to the model but not to the UVs.
6 render smoothed poly model with mental ray.

One more thing: How do you pull up a report that tells you how many polys are in your model?

hi Velusion - I've been importing models into zbrush where you also need quad polys exlusively and i found poly cleanup worked but not by repairing - rather check the option to select non-quad polygons.

I also found my poly count dissappeared with maya 6 (headsup display/polycount) but it returned when I installed the update to 6.01.

Good luck :)