Possibly a stupid question here–

I have a FLIP tank with some action going on. It's just someone diving, so the part of the tank that requires a lot of computation is small, but it's an underwater camera, so with a small tank you see the edges of the simulation. Is there a way to either focus the simmable area in a tank/make particle separation dramatically smaller in one area, to accommodate a huge tank with not much going on so the render times aren't crippling? I've seen tutorials on using lo-res sims to drive hi-res, but that is sort of the opposite of what I'm looking for. I've also seen some endless ocean tuts, but since what I need is an underwater dive, and the breaking of the surface (and the water still beforehand), I haven't found a way to make that work.

Thanks for any help!

Hey Bentway,
You can reduce the bounds of the sim to the area where action is happening and then you can extend it while meshing the surface using particle fluid surface SOP, also there are options to blend the edges with the sim. I guess thats what you are after..

Cool–this looks promising, but the only info I'm finding about this node is the documentation itself and it focuses on surfacing sims themselves. How would I go about extending the sims (or the appearance thereof–extending the mesh) using this node?

How would I use the particle fluid surface SOP (or any other way) to “extend” my fluid tank so that the simmable area doesn't show it's edges/boundaries and looks to be a part of a much huger tank? Or is it just the nature of the beast that one has to sim the entire area, even if only a small area is seeing action?

In the Regions tab of your Particle Fluid Surface SOP, you can specify a bounding box, flatten the surface near the edges of the box, and then extend the edges using Pad Bounds and Extrude Polygons.

Exactly what I was looking for! Thanks!