XM Magdalena 3D print, GGeorgy (3D)
LC #42 Pipers Alley

View Full Version : MR Refraction Issues

10-03-2007, 12:29 PM
Hey guys, here is a scene I'm working on and I seem to be having some problems with a dielectric material refracting.

Here is the render:

I've circled the areas of the dielectric Mental Ray shader which appear black in the render, but should appear near transparent. This is a Realflow mesh exported to .obj, due to the fact that Maya 2008 doesn't support the Realflow plugins as of yet.

My refactions are set to 7, relfections 7 and total 18 under the Raytracing mental ray menu. I've tried increasing the Raytracing values, but to no effect.

Here is a Maya 2008 screenshot:

Any suggestions?

10-03-2007, 12:32 PM
Oh, a "make wet" pedal?

(Sorry, revealing my hidden life as a music producer ;) )

There was an error recently discovered in the Dielectric shader which would probably manifest itself similar to what you describe. Although that should be fixed in 2008. Hmm. How are your normals pointing?

I'd say my classic mantra "switch to mia_material instead".


10-03-2007, 12:35 PM
He seems to be using 2008, so go, go MiA.

10-03-2007, 12:39 PM
He seems to be using 2008, so go, go MiA.

Yeah, just noticed, edited my post accordingly. I dunno how I could read "2008" as "8" originally. I mean, 2000 off? That's bad accuracy ;)


(For those that don't get it, I originally misread the version number and said something like "I'd normally tell you to go to mia_material but you seem to be on version 8")

10-04-2007, 04:46 AM
Thanks for the replies Ole and Zap! I decided to take your advice and switch to a mia_material after having no luck reversing the normals. I think the result worked quite well (in addition to some Photoshop modifications ;))!


Thanks for the help!

10-04-2007, 06:56 AM

Still looks a tad less transparent than real water would.... in the mia_material, either try turning on the "Fresnel" mode (in the BRDF rollout) or just set the "BRDF 0 Degree Reflection" to 0.05 (which ends up very simlar to the facing Fresnel reflectivity of water).

Then you may need to turn up the HDRI for reflections a tad.


10-04-2007, 08:50 AM
Adding some caustics could also be cool. Just some subtle highlights to give it a slightly less CG look.

10-04-2007, 11:22 AM
Once again, I really appreciate the help guys! Here's another render with BRDF 0.05 Degree Reflection. A further improvement! Thanks Zap!


@Ole - I've considered caustics but since I'm running on a very slow machine it takes about 1 and a half hours to render this without caustics. However, its worth a crack ;).

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10-04-2007, 11:22 AM
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