View Full Version : MentalRay GI with Fur

06-26-2011, 04:20 AM
Please advise me what should I do to in my lighting setup or MentalRay setup so that I can render millions of (small in length as well as in width) dense fur (shave and hair) so that I can achieve good defination of fur in my render output specially closeup shots.
I am planning to
use Rasterizer instead of Raytracing for Fur.
Detailed shadows in lights.
Confused about using spot lights or Area Lights (in some post it is written Area lights should not be use with Fur).
I know it is not advisable to use Final Gather or GI for Fur but if have to match my lighting with a back plate,so how could I achieve realistic result .
Faking is an option by using a dome kind of setup but is it viable option what if your environment is constantly changing.
What you guys usually use in production when you have the HDRI maps with different exposure levels and Furry creature.
Is there any tool or option available for this kind of situation in mental ray.

06-26-2011, 05:36 AM
If you are going to go with rendering with the Rasterizer I would simply avoid a lot of raytraced effects (decreases the performance gain), in fact I would try to turn it off and use a lighting rig with detail shadow maps. Tweak the transparency level for the rasterizer to keep it nice but not overly high. Lastly, for hair/fur you can keep the shading rate really low while increasing the visibility samples.

If you are using Maya 2012 you can render with scanline OFF and Unified sampling. Then try Final Gathering, but keep in mind that the Maya hair/fur shaders are old and Autodesk should update them. Use Puppet's (Pavel) shaders for that.

Puppet's Shaders (http://www.puppet.tfdv.com/download/shaders_p_e.shtml)

06-26-2011, 07:08 AM
Thanks Bitter

I also wanted too know does segmented shadows would help me in achieving good Fur or it is just an overhead.
Should I need to tweak shadow map bias unlike 3delight or Prman where small changes in values produces huge differences in final result.
What about Area lights?
Maya Area lights ,MR Area lights or No Area Lights.

Yes, you are right about shave and Hair shader also it does not output any Passes and light linking is another big problem too,I was thinking of using MentalCore from http://www.core-cg.com/ as I find it is easy to install and more organized in structure with proper integration with Maya's render layers,Though I have no idea whether it's hair shader is better than P_hairTK or not. It also provide an interface for Unified sampling but unfortunately I am working on Maya 2011as there is no shave and Hair available for 2012.

P.S .I tried a test with raytracing instead of rasterizer and surprisingly it renders faster with great detailing even though antiailasing contrast was very low with min and max samples values of 0 and 2.I don't understand why and how?

06-26-2011, 07:21 AM
Segmented shadows will help with transparency but hair is so fine and small it might not be enough to make a large visual difference. Might be worth a spot-check if the hair is light colored, very transparent, and thick.

Area lights are nice but can be slow. I would possibly avoid them unless the look is really superior.

If rendering with mental ray, use mental ray native area lights. Keep the high samples limit low as well as the low samples.

Raytacing isn't as slow as most people might think. Your problem without using Unified is that if you motion blur it, it will be painful. That's where rasterization will perform better than regular adaptive. Mental Core is very nice and hope to be using it more often than I currently am using.

06-26-2011, 07:38 AM
Thanks Bitter for clearing my doubts related to MR and it's various options Actuallay because of these doubts I was bit hesitant to use MR for Fur and even tried 3delight but nobody replied to my thread http://forums.cgsociety.org/showthread.php?f=87&t=989400 ,so I again shifted myself MR

I am not having Motion Blur so it would be wiser for me to use raytracing over rasterizer.
Thanks for your unified sampling thread it is very informative.

06-26-2011, 09:59 PM
I was thinking of using MentalCore from http://www.core-cg.com/ as I find it is easy to install and more organized in structure with proper integration with Maya's render layers,Though I have no idea whether it's hair shader is better than P_hairTK or not.

The hair shader in MentalCore is based off p_hairTK, albiet with a few modifications - built in ambient occlusion (both a quick fake and raytraced), support for all renderpasses (including per light passes), built in ramp to control hair colour and some tweaks to play nicely with shave and a haircut. But the specular model is pretty much the same still, so you can get the same results.

06-27-2011, 04:31 PM
One more question to Bitter,what do you mean by Scanline off.
Is it a new option in 2012 or you mean we should use raytracing or rasterizer instead of scanline.

06-27-2011, 04:34 PM
In the mi syntax it's technically Scanline Off.

But in Maya I mean to select Raytracing in the Features section instead of Scanline or Rasterizer.

06-28-2011, 07:31 AM
Does anybody know a way to flush out memory while using Mentalray without closing Maya?

06-28-2011, 07:46 AM
Sometimes you can render a selected tiny object only and it'll work. But that's an old trick. (render selected objects)

06-28-2011, 07:48 AM
I wonder if using a memory cleaner would work?


06-28-2011, 09:35 AM
Hmm I'll try that old trick.
So apart from that there is no script or option which can optimise the data translation process of MR.

06-28-2011, 04:37 PM
Is this a translation issue? When are you running out of memory?

If you have a lot of hairs then it's going to eat a lot of memory, that's just the way it is. (Hair is a special type of curve btw.)

Try reducing them or rendering volume hair.

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