View Full Version : Gremlins inside mental ray

08 August 2004, 10:25 AM
I am having a hell of problems trying to render an organic model i had inported from lightwave and i,m starting to think that the problem is the geometry but i can,t figure why.

The problem is that when i use photons with fg, hotspots appear in the eyes, ears and mouth of the model, some kind of auto illumination, and on another test without photons with the difffusion shader i get extrange results in those areas too.

I have made tests with more simple geometry and i didn,t get this weirds results, so can be something connected with the geometry?

I left here some samples of the tests, the first with photons and fg and second with diffusion.

Thanks in advance.

08 August 2004, 04:37 PM
Although I'm not sure how to help you, from the looks or your second image the darker areas are a reult of overlapping geometry thats cutting off the effect. The eyeballs in the head, the ears just cus of the complexity and overlapping that occurs there in general. The mouth looks like the result of the mouthbag inside the head.. The diffusion shader is really tricky. You'll need to adjust the values till it becomes less noticable. Try gettng the look you want on a shpere first then move to the head, then consider mixing the diffusion shader with a blinn or a phong to better control the affected areas and isolate them.

08 August 2004, 04:50 PM
Excuse my newbness with XSI, (I haven't even started texturing or rendering yet), but could it be a problem with normals? If you hit the "eye" icon in your view, you can turn on normals visibility to make sure that all your faces are pointing out. Just (a newb) thought.

08 August 2004, 05:03 PM
Thanks a lot for your reply 3d43jesse:) i think you are right, seems to be an effect produced in part by the inside geometry of the head, i,m wondering if could be a way to make that the shader doesn,t take the inside geometry in account.

By the other hand the first issue about photons and hotspots has been solved thanks to a person in the xsi base forum that told me that the effect occurs cause there wasn,t an environment and the photon effect bounced on the model itself.

08 August 2004, 11:27 PM
Hazmat thanks for trying to help :) , i,m a newbie with xsi too, i didnt,t know about the option of seeing normals in the viewports, thanks, i have been testing today another sss shader that gives me much better results, its the subscatter.


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