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aandronov
06-27-2012, 03:38 PM
Hello everyone,

I have the following issue with vray's sss2 shader: I want to visualize a grape with it's pit inside. But any geometry placed inside a volume with sss2 renders with sharp contours. It's appearance is not blurry as it should be and that's not what I expected from the refractive raytraced sss mode.
I tried different modes and settings, I even tried fallof map in the opacity channel of the inside geometry to simulate blurriness, but results were all the same even though falloff had it's effect on the geometry itself. On the other hand light sources placed inside sss2 volumes look ok (as we can see in this (http://www.spot3d.com/vray/help/200R1/images/examples/vrayfastsss2/phase_function_09_light.png)example) To me it kinda looks like a volumetric light with fog.

I realize that glossy refraction will do this part of the job. Lower glossiness values give a certain degree of sss-feel (and a feel of time passing so slowly if we use a fair amount of samples), but without the proper volume lighting by scattered light. So how can I combine that with translucency?
Has anyone used the translucency option in the VrayMtl?
Any other ideas for a workaround?

Thanks,
A.
dannyboy374
06-28-2012, 11:33 PM
First off, have you tried setting your scatter to raytraced (solid)? The refractive option is more for clear materials, crystal, etc. check out this guide, it'll show you, and better yet teach you what every single part of the shader does. Chances are you'll be able to fix your issue with the info here.

http://lighting3dvision.blogspot.com/2012/06/vray-materials-by-vis-corbel.html?showComment=1340749104337#c6717704715940251630
dannyboy374
06-28-2012, 11:37 PM
another thing, don't always feel like your renders have to be 100% there, get as far as you can with vray, and use a compositing package like Nuke to do the things that just don't work in 3d (like blurring the pit). 10 seconds in nuke vs hours of headache in maya
aandronov
06-29-2012, 05:16 AM
Hi, dannyboy374 and thanks for your answer,

sure, I tried every mode!

Doing it as a post is a reasonable solution for sure, but I also want to find the "hard" way :)
I had already explored the manual in-depth, so I was pretty sure it's not doable with the fast sss shader, but there's always a chance to miss something.

In the meantime I was able to make some experiments with glossy refraction and translucency options in VrayMtl and I found out that this is the way to achieve an accurate raytraced blurry-pit-in-the-grape effect. However, a great number of glossy refraction samples were needed for the translucency effect itself to look nice, so everything comes at the cost of much higher render times than with fast sss shader. As always, fast emulated looks come at some cost and vice versa.

Thanks,
A.