V-Ray 3.40.07 / Maya 2017 Update 3 / Win10 64
Are there any known compatibility issues with the Alembic cache type and the V-Ray cutter object (in mesh mode)? I’m getting some odd results.
Something isn’t right here.
So there is something wrong with my results. For a the first 20 frame it renders fine, but then the clipper/almebic mix freaks out (see image below)-
This is what my alembic looks like (video)-
ANY dev hit me up and I’ll give you the scene to look at. In short, the cutter is not cutting where the geo of the alembic is in world space. I don’t know if this is a Maya issue or a Vray issue or a user issue, but it’s an issue. Email me at “Clayton.krause@johnsonfit.com” and I’ll hook you up with a test scene.
Best,
Clayton
Can you send the scene to support@chaosgroup.com ? Please mention this forum thread in the message as well.
Thanks!
I wanted to do my due diligence so I completely recreated the cutter object and did another test render. I figured if I made sure all my transforms were frozen before creating the alembic I might be fine. I am just emailing support tonight on this as the exact same issue is happening again with a completely new alembic. The only reason I need to use an alembic is because Maya is glitchy as hell - https://forums.autodesk.com/t5/maya-forum/object-flow-motion-path-maya-2017-update-3-probably-another-bug/td-p/6934515
Good thing I’m switching to Houdini, bad thing that you guys don’t seem to officially support it. 
At any rate. I am emailing support within the hour.
We actually do:
https://github.com/ChaosGroup/vray-for-houdini
Nightly builds and App SDK licenses are available on request. There will also be an official web page on our website soon.
Best regards,
Vlado
Good for you guys! I’m on a trial now of it now, but was curious of the official status as it’s not listed as supported on your website (although in the DL section there is an option to download it). At any rate, good to hear.
I’ve submitted a ticket to support last week, but they are stretched thin right now and couldn’t get to my ticket right away (completely understandable). I wanted to post up more information here in case anyone wanted to pipe in for any possible solutions.
Here are two photos illustrating the issues-
Here is the raw animation the frames were derived from now that you know the troubled issues -
So. Issues related to the clipper
-Motion blur issues (MB coming from a Vray Physical Movie Camera).
-Clipper is cutting into the shell in an area it should be.
-The normals of the shell where the clipper “terminates” seem to be screwy. This could be a conflict caused by Vray round edges? The clipper is set to intersect and only on the shell.
-Odd flicker of the shell right after the 2 second mark on the youtube video.
Any input at this point would be helpful.
Thank you,
Clayton
Hi Clayton,
I just want to let you know that one of our developers is working on your issue and we will get back to you as soon as we have any solution or need additional details.
Please don’t hijack trouble-shooting threads as it becomes very difficult for everyone to track what’s going on; it would be best to post this in a separate thread as the issue is probably unrelated. A scene to go along with that thread will be very useful too.
Best regards,
Vlado
Update..
So I was using Alembic because Maya “flow path object” is broken. It was glitching out at render time so I baked it down to an alembic for this project (normally I wouldn’t do this because it makes things more complicated to change).
Kicking the can over at the Area forum with the devs (who are looking into the issue), I was advised to try “Curve Warp Tool” (<--- EDIT - I wrote the name of the curve tool incorrectly and corrected it) which was recently added to Maya. In summary, it looks to be very similar to flow path object, but actually working correctly.
Did a test animation last night and the weird extra clipping seems to be gone now when not using alembic. Still getting the weird normals at the terminating portion of the mesh being clipped (pointed out in original post in this thread).
Also I’m getting some oddities in what I would assume is GI. It seems like shadow casting gets flickery in some areas (I can post the video up when my computer is free’d up from rendering tomorrow).
Now I’ll be starting another render with camera motion blur turned off, with GI turned off, with all render elements turned off to see what happens. I’ll report back tomorrow.
Thanks for looking into this diligently Chaosgroup team. Support here has always been a big help.
Best,
Clayton
This is now fixed in the nightlies. You’ll get a reply to the email you’ve sent us as well.
Super cool. Thank you for the quick turn around. So it specifically had to do with Alembic? Did the normals of the terminating mesh being clipped get fixed too? Was there an issue with the motion blur? Curious about these things if you have a moment. Thanks!
According to the developers, it wasn’t working with alembics in V-Ray before. It would be greatly appreciated if you could give it a try with a nightly build and see if it works correctly for you.
I cancelled the animation I had rendering to start one over night to test for you guys. Updated to nightly 3.5… in folder “20170317”. I’ll post the results up tomorrow.
Thanks again for looking at this so swiftly.
As promised, the animation is posted below. All but one issue seems to be gone! There is a noticeable flicker right at the end of the alembic animation sequence. Along with the video output I posted two frames (before and after flicker). This is a GI issue potentially and will start another render today with GI turned off to see if the issue is resolved. Even if it is a GI issue I’d presume the clipper operation is the instigator as the flicker happens right at the last frame of the alembic animation. Please advise on this! If I can get this working without any GI I will go for that because of project deadlines, but if the Chaosgroup team can look into why this is happening or offer suggestions to avoid it from happening I’d appreciate it.
VIDEO-
Both Frames together:
Frame:103 pre-flicker:
Frame:104 post-flicker:
Thank you!
Another update after putting together the animation I had going over the weekend without any GI. Still getting the flickering after the alembic clipper object plays through. A good thing to mention is I’m having the alembic hold on last frame. Considering the flicker, light/shadow shift happens at completion of the alembic play through, I’d assume the hold alembic option isn’t jiving well with VRay. I’m going to rebuild the clipper without using an alembic now (since Autodesk cleared things up with their flow object path bug).
I’ll report if anything changes. In the mean time, if anyone here has any suggestions I’d appreciate it. This project has been problematic, but I’m excited to see it almost complete.
Thanks,
Clayton
Hey all. So again, the clipper is clipping the appropriate amount of geometry now with alembic. I still am having a whole slew of different issues here that I don’t really know where to start on. Please advise. If you’d like me to create another thread in “problems” section let me know. I’m going to render this again but without the clipper completely.
So far these are the render variations I’ve tried-
No GI
No GI - No Camera motion blur
No GI - No Camera motion blur - No alembic for clipper (used another solution provided by AD).
I don’t really know what else to do here. This isn’t the next ILM feature film I’m working on, but a really simple scene and I’ve tried to figure out what’s going on through process of elimination on my end. Any further help would be appreciated. I’ve made a video (below) clearly illustrating the issues. Thanks.
Has similar issue to solve it I rendered out all objects separately with Vray object prop node to cut out each object and this stopped my flicker. I would get random flicker just on one frame, previous and next frames were fine I couldn’t work out where it came from.
It didn’t matter if it had GI or not. I had alembic in the scene with a VRay cutter but these two did not intersect at all.
That doesn’t sound too hopeful for my case. I’m not going to butcher up my animation to make it “work”. Thank you for the input though! It does help to know that others have had this similar issue as well. Hopefully the devs can come up with an explanation or a fix or something. 
Right now the last test was void of any alembic as well.