General question about performance (vox/s)

[joshclos]

I'd like to learn more about the "Performance" reading while simulating in build 3.05.00. A higher performance value probably means better and more efficient simulation calculations, right? My test smoke grid is 1.2million cells (non-adaptive) and is showing about 1.12M vox/s. It seems to be using only about 22% cpu usage throughout the sim as well but that may be based on ram requirements together with overall cpu core count or something like that (16 core processor).

My initial assumption was that it measures calculated voxels per second but I'm unsure because my grid is 1.2million and it takes about 1.2s per frame.

Any info is appreciated - thanks!

[Svetlin.Nikolov]

Hey,

We sped up many parts of the simulation, mostly visible in FLIP sims, and there is still a lot more we can improve as you've seen by CPU utilization.

If you are doing a low res sim and CPU is low, then a lot of time goes into writing the caches to disk and reading them for the preview. With higher res grids you'll get better utilization because the sim is not starting and stopping all the time Btw, in Maya there is an option to simulate without caching to disk and it won't be too much work to port it to Max and fix some issues with it, so you will be able to fire off some quick preview sims without waiting for unneeded processing.

The vox/sec is a bit of a crappy metric and I haven't had the opportunity to rework it. It's obviously not correct for FLIP sims where not just voxels but particles are getting processed heavily as well. You shouldn't count on it for anything more than comparing and old build against a newer one, though the total simulation time would be the best metric anyway

Btw, there is also a new option in the Max nightlies at the top of the preview rollout, which allows you turn off preview reading of caches during sim, or even completely unless you are rendering. Of course grid texture and interacting sims will keep reading caches, but most of the slowdown comes from the preview, so this might give you some 10-30% speedup too, especially for overnight sims where you are not constantly looking at the preview anyway.

Hope this helps!

[Svetlin.Nikolov]

Ah, something else which is very important I forgot to mention - scene interaction is mostly single-threaded because Max and Maya can't really handle many kinds of multithreaded access to the scene. We can do a lot to improve interactions with large meshes, but for example the Max forces such as the Wind, Drag etc can't be read from all cores simultaneously so there is no hope for some of the processing (at least as of now).

[joshclos]

Very good information, thanks so much! The option to disable cache previews is a great idea, thanks for adding it!

[Svetlin.Nikolov]

Hope it helps save some time Gotta port it to Maya as well, and sometime soon we'll be onto speeding up saving the caches as well, there is a lot we could squeeze from that process too, but we have to watch out not to lose the relatively small cache sizes..