Constant fluid integrity over varying Voxel Counts

#1

I was wondering if there was any way to keep the fluid size constant through varying voxel counts. I’ve been messing around with Maya fluids for a couple of days and have learnt a lot! Just haven’t been able to figure out how to have the lower quality roughly the same size as the higher.

Here are some images of what I mean, both taken at the same frame and have the same settings, but with varied voxel counts:
100 voxels: http://imgur.com/i5BhGNL,5yJISy3#0
200 voxels: http://imgur.com/i5BhGNL,5yJISy3#1

I understand that upping the voxel count refines the solver, and its essentially just a proxy estimation, but hate the concept of the look changing with the voxel grid.

Obviously I want them to both be the same size just varying qualities, is this possible?

#2

From my experience not really and perhaps Duncan can offer his expert advise on exactly why. But when you think about it it makes sense. If you add more voxels then the evaluation of attributes such as velocity swirl and turbulence are changing at a higher rate than they would normally so of course this will affect your simulation.

Actually there is a workaround and thats using SOuP upres node. I assume you are just after more detail without losing your simulation and thats just what the node is for. So instead of increasing the fluid resolution, you keep the simulation but increase the detail in another fluid container. Sim times of course increase but you can cache out the sim fluid when you are happy and then pipe it into the upres’r.

#3

Jeremy’s points are good ones, and you may find the Soup upres useful. Maya attempts to preserve behavior when voxel resolution is changed, but there are a lot of variables and as well the simulation will never be identical. Some problems might be due to dropoff from an emitter… the higher resolution might result in more or less emission, which can have dramatic effect.

When you increase the voxel resolution sometimes it helps to also increase the substeps… in order to preserve the speed of motion across finer voxels it takes more iterations in time, particularly if you are using auto resize. If your simulation has high dissipation rates you may also need to enable “emit in substeps”.

Duncan

#4

This works extremely well!
:smiley:
https://vimeo.com/70423554

I too am surprised its not been thrown around more… definitely going to use this more often! (Until Bifrost destroys all my Maya Fluids knowledge :wink: )

Not perfect and wont work in all situations but is a cool trick for blocking out quick low res fluids for approval and then ramping it up for final! :smiley:

#5

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