I have a big container with 300X250X1100 with 200 uniform divisions, the simulation for my smoke were not slow to be done and it's already on cache.

When I try to render it even with low samples and low shadow map settings it takes really a long time to render, considering that I already used the same container setup but using smaller size for it, the same rendered much faster.

I know that seems obvious but I am going to ask anyway if the size of the container matters on render time even if the fluid SIM is not using the whole space in it?

Any tip to optimize this?

Thanks.

Try decoupling and increasing shadow step size on the sampling tab of your rop.

If you're using the default, Houdini is sampling every 0.1 metres. If you have a large volume that is a lot of samples. Try bumping it up to 1 or 2.

I would also increase the volume step size. I generally use a volume step size that is half of my shadow step size.

WOW!!!

That's it, Thank you very much kacheson!!!!

I didn't find the decoupling option on Houdini 11, but the shadow step size solved my problem.

Cheers!