non homogeneous sample distribution

[psanitra]

Hey guys. I`m rendering a lot of volumes with volumegrid shader, and i`m having hard time getting homogeneous sample distribution over the whole image.

I`m observing this behaviour for some time, where volumes are much cleaner then rest of the scene for give noise threshold. It does not matter if i use 0.5, 0.1 or 0.02 , volumes will be cleaner then the rest of the scene.

Is there any local sampling control, or relative pixel variance control(in Renderman terms) that i could change to get more noisy volumes on purpose? Grid step is obiously not the control to use. I`m talking about control for number of samples/rays or noise threshold.

Just to rule out any hack/tricks, i`m not using volume light cache, not using probabilistic, and using raytraced GI scaterring type.


So what do i do to get more noisy volumes?

thank you!

[Gosho.Genchev]

It's a known 'quirk' of adaptive sampling with volumes - they are indeed oversampled for a given noise threshold - there isn't much you can do about this. I've had some success speeding up our test scenes by setting the DMC Sampler's Adaptivity and Noise Threshold to 1, and Min Samples down to 2 but realistically, such settings are not suited for a production render.

I'd be really grateful if you could share a scene with us that shows this in a realistic scenario.

[psanitra]

Hm, that`s bad news.It would be great if you can give us some local controls, on shader on per objects. Simplifying sampling and automating sampling (Vray 3 and on) it`s a nice thing, until it`s not . I really like the RM solution with relative pixel variance control per objects. It just works. I set it to 2 and my 0.05 is 0.025. Really nice.