Problem with animation prepass irradiance files

[jasonazure]

Hi, I hope you can help me as I'm am rapidly approaching delivery and I have a complete killer issue.

I am using Maya 2015 SP6 and I was using Vray 3.00.01 (I have since installed 3.10.01 but the problem hasn't resolved)

Basically, I did an 'animation prepass' to get a set of irradiance files which I then did a render from, but when I watched the render back there were some strange artifacts and flickering. I used the 'Irradiance Viewer' to look at the files that were saved out and it seems like whilst the irradiance is applied to the moving objects in the scene correctly, they jump back to the position, rotation etc. that they were in on the first frame of the batch before the irradiance map is saved out! As you can imagine, this creates a complete mess when the final rendered frame is produced using these files.

I have used this method before with this version of Maya and Vray, so I can't think what's broken it apart from one of the Maya Service Packs. Have you any experience of this problem, and if so can it be fixed easily? I'm deep into a project, so the last thing I want to do is have to upgrade my Maya to 2016.

[Morbid Angel]

Hmm...Are you using animation mode? In which case if you have moving objects you should have irradiance map per frame. In any other model it won't work. I don't think that updating to new maya will solve the issue.

[jasonazure]

I was using medium animation and it was animation pre-pass mode! As I said, I've used this before and it's worked fine.

[jasonazure]

Admin - I tried to see if any nightlies builds would fix this issue, but I don't have access to the Maya builds at all. Could you allow me access please? (For some reason I do have access to Blender Vray builds which I don't use!)

[jasonazure]

OK! I think I'm going mad now! I just installed Maya 2015 on another workstation, and not patched it, so it's SP2 and then installed Vray 3.00.01.
The problem is still occurring!
What the hell is going on?

[ivaylo.ivanov]

It's best to send the scene to the support so they can investigate.

[jasonazure]

I've sent a file, but after playing with a simple test file, I think I've worked something out!

When using the prepass/render workflow across a render farm, do the frame batches have to be the same ie. if frames 10-20 are generated by one machine in prepass mode, does the final render batch have to be 10-20 also?

[tashko.zashev]

I've sent a file, but after playing with a simple test file, I think I've worked something out!

When using the prepass/render workflow across a render farm, do the frame batches have to be the same ie. if frames 10-20 are generated by one machine in prepass mode, does the final render batch have to be 10-20 also?

Hi,
You should have a reply to your support ticked about this issue.
Regarding the batch render question, you can always render a part of the frames you need. For an example 500 frames pre-calculated GI and at render stage you can set only frames between 100-300.
Assuming this is what you asked for.

[jasonazure]

My question was more to do with batch numbers when rendering across a number of machines. Because, when you create Irradiance files for an animation, say from frames 10-20, when you view the vrmap files using the irradiance viewer, the data for each object is placed where the object was at the beginning of the batch i.e. frame 10

[tashko.zashev]

What I understand is that all .vrmap files/frames are identical and contain information only about frame 10 in this case. Please correct me If I'm wrong.
Would you please provide more details on how do you setup the network batch render for the GI prepass ? Do you use a render manager or using our Distributed rendering ?

I can't replicate this issue here when batch rendering on single machine.

[jasonazure]

Hi,
I had to leave this problem and just live with the flicker as I had to get something delivered, but it never really got resolved!
I have now had to re-visit the whole GI animation prepass thing for a current car project and after a day of messing around with it, I want to officially declare this as a bug!
Basically when Maya batch rendering, something to do with animated object positions doesn't get updated in Vray properly, which means that if I render a set of prepass Irradiance frames, for example 5-9 using Maya batch (controlled by BNR - Butterfly Net Render) then I look at the files using the irradiance viewer, I can see that the positions of the moving objects are the same over those 5 frames i.e. they are stuck at frame 5 position. Then if I have a batch rendering frames 10-14 all the irradiance information for the moving objects are at the position of frame 10. This causes real problems when blending irradiance files from other batches as there is a big jump between positions. I had this happen today, where I rendered 5-frame batches across my render-farm using Maya batch render for the prepass and then the render. When watching the animation back I could see the shadows drift away over 5 frames and then pop back into position every 5 frames!
This problem is so easy to re-produce, I even got it occuring when using the Vray animation option in Maya on a single machine.

[jasonazure]

P.S.

I do have a workaround for this problem now, but it's not very satisfactory.

Basically, I just render the animation prepass and then final render using a batch size of a single frame. This works, but sometimes my scenes can be 3-5 Gigabytes in size and take over 4 minutes to load, so when I do load one, I normally like to get a batch of 5 to 10 frames out of it, before I have to re-load it. Using my current workaround means that every frames render time would have 4 or more minutes added to it PER PASS!

[Svetlozar Draganov]

If it looks like a bug we definitely would like to reproduce and fix it.
First please make sure that the issue is reproducible with the latest official version of V-Ray.
If it is please send the scene again, I know you sent it a few months ago but it would be very difficult to find it if not impossible.

Give us a detailed description of the rendering workflow that you are using, so we could follow it and execute the same steps into our environment.

If possible please execute one test without Butterfly Net Render in order to exclude it from the suspects. Let us know if the issue is still there even without using BNR.

[jasonazure]

I will get together some test renders that show the problem, plus some test scenes to reproduce it. It seems to do it all the time, so won't be hard to reproduce!

[Svetlozar Draganov]

That's great. Feel free to send the scene over when ready.