vray 5.1, low cpu usage in simple but slow scene.

[super gnu]

im doing a quick super basic test of the new caustics.. a couple of torus knots slowly rotating above a plane, with a vray sun.

on a 3990x i get maximum 40-45% cpu usage. seems to be the same with or without caustics.. ive played with the min subdivs etc, but its just not using my cpu...

I can kinda accept its not a realistic production scene (ive tried on a "proper" old scene with loads of textures and it hits 100% constantly..) however, given that with caustics on its really slow to render (ive not let an image finish to default noise thresh. - id hoped it would be faster) , having 60% of my cpu sitting doing nothing is a bit silly, and makes testing animated caustics unrealistic even in this simple scene..



any suggestions?

[^Lele^]

Is NUMA active?
If it is, can you test turning it off?

As for speed: the one with caustics is unfortunately expected for this release stage of the feature, it'll hopefully get better with a bit more (planned) work.
Still, with 8 cores and no NUMA on your scene i was on average with 85% usage.
So perhaps you can try splitting the cpu up in more than one VM and render more than one frame at once (wild poke at manual load balancing.)?

The one without caustics is due to having fewer pixels to work on than threads (as you have a big, featurless area, and no major highlights), so the adaptive sampler does the best it can do with what's there.
For that there's not much that can be done (besides feeding the beast -as you tried- with more complex stuff.).
Check a samplerate RE for that, you'll see.