MR hates my model

# 1 16-10-2004 , 04:03 AM

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Join Date: May 2004

Location: Utah, USA

Posts: 369

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

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# 2 16-10-2004 , 04:37 AM

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Maybe quadchecker will help you out. Check this thread.

"Terminat Bora Diem, Terminal Auctor opus."

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# 3 16-10-2004 , 04:44 AM

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Join Date: Mar 2003

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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.

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# 4 16-10-2004 , 04:57 PM

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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..

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# 5 17-10-2004 , 03:30 AM

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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?

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# 6 05-11-2004 , 09:37 AM

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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 user added image