Gustavo is correct, crank your Mesh Splitting Factor in the MR options to something high, problem solved
a _____ From: softimage-boun...@listproc.autodesk.com [mailto:softimage-boun...@listproc.autodesk.com] On Behalf Of Ola Madsen Sent: 20 March 2014 08:11 To: softimage@listproc.autodesk.com Subject: RE: Mental ray volumetric shader errors I don't think that worked in my scenario as I had numerous overlapping objects (was doing an x-ray shot) and I got the artifacts in the overlaps as well. Though this was easily fixed by splitting the scene in a couple of passes. o From: softimage-boun...@listproc.autodesk.com [mailto:softimage-boun...@listproc.autodesk.com] On Behalf Of Gustavo Eggert Boehs Sent: Thursday, March 20, 2014 12:44 AM To: SI mailing list Subject: RE: Mental ray volumetric shader errors Hey Fabricio, i'be bumped onto that also, in my case it was the Mesh Splitting kicking in. It separates dense meshes into separate objects before passing them on to MR. Therefore, some shaders get artifacts, like volumetrics and bumpmapping also. Real headache but easy fix... Under MR > Optimizations, look for Mesh Splitting Factor, increase the value up to infinity and be happy :D Em 19/03/2014 19:20, "Ola Madsen" <ola.mad...@digitalcontext.se> escreveu: I can only confirm this nasty little bug as I experienced it a couple of years ago. If I remember correctly I managed to get rid of the artifacts on some objects by actually tessellating the geometry instead of using to + key. Some object still had the artifacts and I had to work around it by splitting the scene and rendering the objects in in different passes. Cheers Ola From: softimage-boun...@listproc.autodesk.com [mailto:softimage-boun...@listproc.autodesk.com] On Behalf Of Fabricio Chamon Sent: Wednesday, March 19, 2014 11:05 PM To: softimage@listproc.autodesk.com Subject: Re: Mental ray volumetric shader errors ...forgot to say that I'm using "Particle_Volume_Cloud", which used to work fine on meshes since always. 2014-03-19 18:56 GMT-03:00 Fabricio Chamon <xsiml...@gmail.com>: Hi, I'm trying to do some volumetrics in mray, but the shader is giving me all kinds of wierdness on heavy meshes. Have anyone experienced this before ? For the sake of simplicity, I have this test scene with only one default sphere. If I crank up the sphere U/V subd to 200, it starts to show some strange black areas. At subd 300, it renders all flat. I'm guessing it's not a lookup table cell size problem...tried very small values, and the volume renders almost completely solid (when it works). here's some images to illustrate: Imagem inline 1 I really need dense meshes because I want the fine control over the volume silhouette to be on the mesh itself, not through shader trees. anyone ?
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