Particle Alpha Problem

[radobe]

Hello,

i have a problem rendering nParticles with vRay.

The first frame in a render task in deadline is often (not always) rendered with a wrong alpha. I setup a test scene to show the problem, although in the test scene even the rgb information of the first frames rendered is wrong at the beginning. Same things is happening when rendering locally with batch render, often (but like mentioned not always) just with the first frames.

We have a couple different machines in the renderfarm, happens on all of them.

Maya Version is 2013 SP1
VRay Maya 2.40.01
Windows 7 64 bit

EDIT:

Just to explain the sequence further. It was rendered with a task size of 2 frames, thats why the errors occur every 2nd frame.

[tashko.zashev]

Hi,

Thank you for providing the scene file for tests.
Do you mean with "wrong" empty ? In our tests every second frame rendered via Deadline is empty.

We are trying to find the reason for this issue now and as soon as we have any new information will post here.

[radobe]

Hi,

usually they are not empty but have a different opacity, maybe because we are most often rendering with motion blur, just for this test i deactivated it.
Its interesting that its every second frame on your test. I always experienced it to be the first frame of a task, so sending a scene to render just on one machine resulted in just the first frame to be broken.

Thank you,
Radoslaw

[tashko.zashev]

Hi,

In our tests every new frame task (Deadline) starts with empty frame. The particles cache files cannot be loaded for some reason.
According to our tests, the reason for this is not in V-ray. The native Maya Software renderer has the same issue and most probably this is limitation or bug related to Maya.

To workaround this you can disable/remove the particle cache files and render the animation using Deadline again.
I hope this helps you.

[radobe]

We ended up rendering with Arnold and have not experienced any problems so far. Removing cache files is not really an option...

Btw, this happens also with batch rendering locally. It is not only related to deadline.

Hope this will get solved at some point, the way it is now we cant render particles with VRay.

[vlado]

We ended up rendering with Arnold and have not experienced any problems so far.

Ouch, that hurt Still, we'll try to get to the bottom of this - V-Ray has not been used too much for particle work so I expect that there are a few wrinkles that need to be ironed out.

Best regards,
Vlado

[radobe]

Thank you

Radoslaw

[yolov]

Hi there,

We've been running some more tests on this and figured out something odd. Actually all versions of V-Ray will render this scene with a blank first frame, but only on Maya 2013. If we run any V-Ray version on 2014, it renders fine. So I'll post here when we have a fix for that problem.
Now I'm wondering if you still used Arnold on 2013 Maya?

[radobe]

Thats really odd. Yes, we are using Arnold on Maya 2013.

[yolov]

Oh well, I guess the only thing left is for us to fix this for the Maya 2013 builds Will update the thread when I have more info. And thanks again for all the info.

[Lyubomir Rusev]

Hello,

A fast solution to this problem is to turn on "Post Cache Ramp Evaluation" which is located in "nParticle -> Caching". This solution is also suggested in the following CGSociety thread:
http://forums.cgsociety.org/archive/...t-1094854.html

[radobe]

I will try this, thank you.

Radoslaw