displacement?

[gregvfx]

Displacement and RT?
What is there to know?

The render is taking forever to start... when in Adv it ok...
Wouldn't it be better to do the displacement in cpu and send the mesh to RT? or maybe that's what is supposed to happen?
what about cache normals?

[a7az0th]

Adv uses different type of displacement than RT. In RT (GPU) 2D Displacement is not supported. Subdivision and 3D are. When rendering on GPU the Static Displacement option is always considered ON, no matter what's selected in the UI. Same goes for Cache normals unfortunately, so if you want to achieve results comparable to RT CPU, you would need to crank up the displacement quality settings.

[gregvfx]

Thank you.
It doesn't explain why the rendering isn't starting on gpu. Is it because it takes forever to send the geometry to the gpus? Couldn't you have the subdivision done on the fly by gpu? The memory footprint would be lighter at the expense of longer rendertime. But saving memory is so important with gpu rendering...

[a7az0th]

Well, since displacement is done on CPU, the speed would depend on your processor capabilities. Have you tried rendering the same in RT CPU? The preprocessing times should be comparable. GPUs are designed in a way that makes displacement there highly inefficient. This is why we have taken this approach. We are looking into possibilities to improve this in the future.

[gregvfx]

precisely, in Adv the render starts quite normally, when in RT I didn't have patience to wait more than ten minutes without any pixel moving...

[a7az0th]

This is troubling. Such high preprocessing time are not expected. Which version of VRay are you using? What are your displacement settings? Is there a way you can send a scene to the support team for investigation?

[gregvfx]

unfortunately the computer crashed soon after... probably related.
It was just a test so I didn't bother to find the autoback...

But it is on the currrent 3.5 Beta 2

[a7az0th]

Too bad. This is in no way expected behaviour. If you stumble upon this issue again, please report it to our support team so we can investigate further. We will try to reproduce it here, but without knowledge of the settings at the time of the issue, it might be hard to recreate.

[yolov]

If you have a scene that reproduces the problem, could you send it over at support@chaosgroup.com and put the name of this thread in the subject, please?
We'd be interested to have a look what went wrong with that scene and fix any potential bugs.

[gregvfx]

Can't exactly reproduce the forever hanging thing, but with my current test scene I found that if cache normal is unchecked in VRayDisplacementMod it is very unstable and takes a lot longer.
Could it be that RT isn't overriding this property?

[gregvfx]

actually, it is very unstable...
it hangs after stating building static tree very often, hard to predict.

https://www.dropbox.com/s/aa1n9cmbt6...est01.zip?dl=0

[tashko.zashev]

Hi,

I just downloaded the scene file to test it here and when render it in Active shade mode everything seems to work fine. I didn't get any freeze or hang issues at all. But the scene crashes with Unhandled exceptions every time I start to render RT in production mode (for CPU and GPU). Have you noticed this in your environment?

Another issue I've found is the that the message window sometimes stuck on

even if the render has begun.

[gregvfx]

It is also randomly crashing in active shade on my side...

[tashko.zashev]

It is also randomly crashing in active shade on my side...

We have fixed the RT crash with this scene setup for the next service pack release.

[gregvfx]

Good!
Meaning will be available in a nightly?