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Reducing simulation times when iterating


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Any FLIP experts here? Looking for ways to speed up sims when iterating with different parameters. In the past I tried simply increasing particle separation but it always changed the look of the sim at the same time. As mentioned here (see Alen Milanvic's comment).
Now I realize it's related to world scale.
Other than turning substeps off is there any other way of reducing sim times? Some equivalent of reducing resolution when you render.
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After a few lower res tests, I find it best to work in a res close to your final, but work on a very small patch and just become a robot, tweak an attr, do a quick test, understand what raising or lowering a little does, re-read some docs, scour some old tuts for nuggets, do more tests, repeat, a lot. A LOT. :D  After a while you will know within a few frames if something is completely off or not. 

Or Wedge like there is no tomorrow.

But for initial tests and understanding what to tweak, I find it just easier to do small tests quick then once you "feel" it, wedge a few variations.  

Also as far as reseeding, you really need to do some tests and it depends on what you need, like an ocean vs a blood splat and how to use reseeding and oversampling.  Sometimes its better to use very low thresholds.  Again tweak a little and notice how .5 vs .1 reseeds, watching the Geo Spreadsheet.  See how many points per frame you're blasting into your sim.  Is it way too many? Tweak!


Edited by HM_2020
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Thanks. Could you elaborate what you mean by 'work on a very small patch'
Do you mean temporally as in just say a few frames of a 20 second sim, or do you mean spatially?
Also by res I assume you are referring to particle separation.
Is there a rough guide as to what works best for different scale sims? i small scale splashes vs landscape sized ocean sims?

Edited by art3mis
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Spatially.  Like when testing an ocean, with whitewater foam, make a small patch so you can iterate faster.  Or if you need to do a beach wave crashing, a thin sliver of a beach for testing.

Yes par sep for res.  You can also play with Grid Scale and Particle scale, sometimes I have found you can get a good setup, and maybe jack up Grid Scale a bit and still get same results with faster sims.  Also look in the Volume Motion/Solver tab, for Mass and Space Scale and tweak accordingly to your scale if you lets say have to sim at 10x/.01x scale.  

Forgot to mention to save time, filecache any and all colliders and things (perhaps emitters, VDBs, etc) that take a little time to recompute every time you do a test (if they havent changed). 

Pretty much though many different fluid effects require different setups, and its all about as I said just getting a "feel" for how to 'tweak the knobs', so you arent wasting any time with crap you dont need.

*and I would never really do a full flip sim for landscape sized oceans ;) use a spectrum, do some ww sims on it, done.

Edited by HM_2020
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