Force random sampling noise pattern when re-rendering frames

[dgruwier]

I would like to request an option to always randomize the sampling noise patterns, even when you re-render the same frame, instead of only when you change the current frame.

It can sometimes be difficult to judge how much of the visual noise in a render is actually caused by low rendering quality, which can be a problem when optimizing renders for animation. This sparkly car paint material, for example:



The only way of judging the rendering quality of this image is to render it twice with different sampling seeds, and compare the two renders to see how much it changes between them. Same goes for things like fireflies, GI-splotches, boiling highlights, artifacts that are usually difficult to spot when just looking at a still image. Even just plain old Monte Carlo noise

But currently the only way to get VRay to use different sampling seeds like that is to change the current frame. And I'm almost always working with complex animated shots with lots of alembic files and simulations and keyframes in the scene, so "pausing" the entire scene just to check rendering noise is impractical at best.

So an an option to randomize re-rendered frames would be very useful when tweaking render quality

[LarsSonparsson]

Does this help?

https://forums.chaosgroup.com/forum/...eed-expression

[dgruwier]

Absolutely, thanks! I'll try that with the seed value randomized in the script. I guess all that's left is to make it a convenient checkbox in the interface.

Although I wonder if things like the Light Cache would be affected by the DMC seed?

[yolov]

It should not affect the light cache. The seed is for the DMC sampler only. It should affect all samples for ... pretty much anything (shadows, reflections, etc), while the light cache happens before the actual rendering.

[dgruwier]

Just tested it and the script to randomize the seed is perfect, it does exactly what I needed. So much easier to see what's going on with the render quality when you can see how much the image changes between re-renders. And it looks like the light cache calculation only change when you move objects or the camera anyway, so never mind about that.

In the end, all I'll ask for is to make it an option in the interface for convenience. Perhaps in place of the "Animated noise pattern" checkbox in the DMC sampler panel, there could be a dropdown like:

Randomize noise pattern
>Frame change and re-render
>Frame change only
>Disabled

[yolov]

I've logged your request with the developers.