Simulation threads, substeps, frame rate, CPU load, and simulation speed are important variables in conjunction with RealFlow. First, letLet's clear up the relations between all these terms.
Simulation Threads
This number represents your computer's number of CPU's or cores:
- If your computer supports hyper-threading you will see a higher value.
- Threads can be adjusted for each scene individually under → Simulation Options > General.
Under some circumstances you will notice that RealFlow uses only a fraction of the available cores and CPU load is just around 10%. This is typically the case with low-resolution fluid simulations:
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With more than 32 threads you will hardly see any performance boosts, because computer systems do not scale linearly and there is always a limit.
FPS Rate and Substeps
A common question is why simulations with a high FPS rate require less substeps? The answer is precision. The length of a single substep is calculated as
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lengthsubstep = 1 / ( 400 * 300 )lengthsubstep = 0.0000083 s.- So we have a much higher precision:
0.0000083 s vs. 0.0001333 s
In order to get the same precision as before, substeps can be decreased:
- In this example, the FPS rate has been increased by a factor of 16.
- Therefore, the number of substeps can be calculated as
300 / 16 = 19 - So with 19 substeps and 400 frames per second fps we get the same level of precision as beforewith 300 substeps and 24 fps.