Refraction limit...

[evanerichards]

So I have this element I'm rendering. It is an ST pass for generating refraction in nuke. The problem is, it seems that maybe vray can't handle so many layers of refraction? Parts of the image just go completely black. I'm adding refraction on to particles and perhaps there are too many? Take a look at the examples.

Here is a pass. Notice the huge amount of particles at the top. Everything looks correct here.


When I turn on more particles at the bottom however, parts of the image start to go completely black.


Am I doing something wrong? Is there a dial I can adjust to allow more levels of refraction?
Please advise.
Thanks!

[t.petrov]

Yes, there is. It is called "Max. transparency levels" and it is available in the global options.

http://docs.chaosgroup.com/display/V...tions-Geometry

[georgi.zhekov]

There is an option under the refraction settings of the VRay Material called "Max depth" - by default it is set to 5 - so bump it up and it should fix your problem.

Best regards,

[evanerichards]

I SWEAR this was the first thing I tried when I first encountered this problem. But it didn't fix it.
But now you say this is how you solve the problem, I go back in and try it again and it works this time.
Typical.

Thanks!

[evanerichards]

Ok, so I'm on another scene and the same thing is happening. THIS time though I have both material refraction "Max Depth" and global "Max. transparency levels" cranked to the max (1000) and it's still happening. Turning up the max refraction depth on the shader actually made the problem a lot WORSE if that makes any sense or is any kind of clue as to what the problem is.

I'd upload the scene except I've got two sets of cached particles and one of them is over a GB.

Any thoughts?

[georgi.zhekov]

We'll have to investigate this - I really have no idea what might cause it.

[vlado]

I'd upload the scene except I've got two sets of cached particles and one of them is over a GB.

We would really need a scene for this. If you email us to support@chaosgroup.com our support guys can give you our FTP info to upload it.

Best regards,
Vlado

[evanerichards]

I can try that, I can also see if I can just delete the cache, and get the same result. That way I could just upload a much smaller scene. Give me a day or so and I'll try to have a scene for you.
Thanks!

[evanerichards]

Ok. Lets try this.
Here's a scene that seems to be exhibiting this problem. Make sure to render the ST_Refract render layer. One of the earlier frames when the objects comes onto the screen.
Let me know if you are able to reproduce the problem.
Thanks!

RefractionTest.zip

[ivaylo.ivanov]

Turned out V-Ray is limited to 150 refraction depth. I think this was a safety precaution, but it causes such situations. I will see if it can be removed ot at least increased.

[evanerichards]

That would be great! Thanks!

[ivaylo.ivanov]

For the next nightly builds (both 3.10 and 3.15), the refraction will be limited additionaly only by the max transparency levels option. Currenlty it's 1000 which seems enough for your scene.

[ivaylo.ivanov]

Just some note here. Bigger refraction depth may crash Maya on OSX. The issue is that V-Ray may not be able to work in the recursion limit imposed by the OS. We are still investigating for a working method to increase it.