I've seen this sort of behavior as well. In my case it had to do with having camera and cube perfectly aligned -both with orientations zeroed out, or 90 degrees for instance- or the camera being close to one side of the cube, looking straight at it. Same when going from outside to inside a volume, at the moment you are intersecting the side. It's a situation you easily run into in a test setup, or when rigging the camera in certain ways. I think MR is trying to be smart and cull a few triangles intermittently (despite render settings), which messes with the volume - but that's just my interpretation. In any case, adding a very small rotation to either cube or camera, say .001 on some axis, eliminated the problem for me. It's worth a shot. (With a particle cloud the bounding box is always aligned with the world axis - so you'd have to rotate the camera)
-----Original Message----- From: Morten Bartholdy Sent: Monday, November 21, 2016 10:28 AM To: softimage@listproc.autodesk.com Subject: RE: Particle volume rendering problem I don't know what is going on, but it could look like bounding box issues. In Arnold and Redshift if the bounds are not set correctly for volumetrics, I get something similar, only very consistently and not random. MB > Den 18. november 2016 klokken 20:36 skrev Sven Constable > <sixsi_l...@imagefront.de>: > > > sorry, broken links > > > > http://www.imagefront.de/tmp/correct_frame.JPG > > http://www.imagefront.de/tmp/problem_frame.JPG > > http://www.imagefront.de/tmp/problem_frame_w_phong.JPG > > > > > > From: softimage-boun...@listproc.autodesk.com > [mailto:softimage-boun...@listproc.autodesk.com] On Behalf Of Sven > Constable > Sent: Friday, November 18, 2016 8:33 PM > To: softimage@listproc.autodesk.com > Subject: RE: Particle volume rendering problem > > > > Did some more tests and it looks like it's not even the shader. Problem > accours also with a standard phong. Interestingly the shape of the cloud > changes(!) when rendered with a phong shader. > > > > some pics: > http://www.imagefront.de/tmp/correct_frame.JPG > <http://www.imagefront.de/tmp/steam_BTY.mp4> > > http://www.imagefront.de/tmp/problem_frame.JPG > <http://www.imagefront.de/tmp/steam_BTY.mp4> > > http://www.imagefront.de/tmp/problem_frame_w_phong.JPG > <http://www.imagefront.de/tmp/steam_BTY.mp4> > > > > Maybe I'll check with another renderer when I have time. > > sven > > > > From: softimage-boun...@listproc.autodesk.com > [mailto:softimage-boun...@listproc.autodesk.com] On Behalf Of Schoenberger > Sent: Friday, November 18, 2016 11:32 AM > To: softimage@listproc.autodesk.com > Subject: RE: Particle volume rendering problem > > > > Please reduce the lookup table size of the shader. > > See "Lookup Table" and "Setting up Lookup table": > > http://softimage.wiki.softimage.com/xsidocs/particles_shaders_ParticleVolume > ICE.htm > > > > > > > > > > Holger Schönberger > technical director > The day has 24 hours, if that does not suffice, I will take the night > > > > > > > _____ > > > From: softimage-boun...@listproc.autodesk.com > [mailto:softimage-boun...@listproc.autodesk.com] On Behalf Of Sven > Constable > Sent: Friday, November 18, 2016 1:57 AM > To: softimage@listproc.autodesk.com > Subject: Particle volume rendering problem > > Hey list, > > > > I did some tests for an upcoming project and rendering doesn't work as > expected. Just basic ICE particles with built-in nodes and some deformers > on > the pointcloud. Rendered with mental ray. > As you can see in the vid, there are render problems. Sometimes it looks > like missing tiles in the rendering but mostly it seems to be missing > particles in the cloud itself. In this video there are all missing at the > bottom but in other tests it happened also at the top and sometime at the > sides of the point cloud. Never inside the cloud. And it only happens at > render time. No particles are missing in the viewport. > > > > http://www.imagefront.de/tmp/steam_BTY.mp4 > > > > What I tried so far: > > > > Eliminated render farm problems: Rendered it locally on the workstation. > > > > Possible caching problem? Rendered it on a workstation on the fly without > any caching. > > > > Tried playback caching as well as the manual 'write cache' via the cache > manager. (unlikely since it also happens with no caching at all) > > > > Put the point cloud to global zero with no offsets in SRT. > > > > Changed most of the MR render settings. Including switching to BSP1. > Disabled On Disk Framebuffer. > > > > Changed settings of the volume shader ( specially the bounding box size > for > the voxel computation. Set it to manual instead of Auto because the > missing > parts always appeared at the perimeter of the cloud). I also changed most > of > the other settings that possibly could have an effect. > > > > Tried both built-in particle volume shaders, 'Particle Volume Cloud' and > the > basic 'Particle Renderer'. (btw. the volume cloud shader by Holger > Schoenberger is amazing) However, it gave me the same problems. > > > > Reduzed the particle rate (this is the video showing different particle > counts but it happens in all versions as you can see). > > > > > > I'm pretty much out of ideas. Anyone? > > > > Thanks, > > sven > > > > > > ------ > Softimage Mailing List. > To unsubscribe, send a mail to softimage-requ...@listproc.autodesk.com > with "unsubscribe" in the subject, and reply to confirm. ------ Softimage Mailing List. To unsubscribe, send a mail to softimage-requ...@listproc.autodesk.com with "unsubscribe" in the subject, and reply to confirm. ------ Softimage Mailing List. To unsubscribe, send a mail to softimage-requ...@listproc.autodesk.com with "unsubscribe" in the subject, and reply to confirm.
