Simulation Settings

Owned by thomas (Unlicensed)
Last updated: 16 Oct, 2018 by Alex Ribao
2 min read

RealFlow | 3ds Max's simulation settings are located under the "Scene" object's "Global" tab. During your daily work you will mostly deal with "Substeps" and "Iterations":

  • Substeps determine the quality of the simulation.
  • More substeps mean better, more accurate results, but also longer simulation times.
  • The default settings ("Auto Params") work very good in scenes without interacting objects, e.g. pure liquid or granular simulations.
  • In conjunction with collision objects, the default values are normally not sufficient.
  • Increase the substeps in moderate steps, e.g. by 2 or 4 until you get the desired result (valid for → Liquid - PBD, → Granular, → Viscous, → Viscoelastic).
  • The→ Liquid - SPH fluid type works with rather high substeps already (Min = 1, Max = 300) and here it is normally not necessary to increase the values unless you work with high "Viscosity" settings or when particles go through → interacting objects.

 

 

Iterations are relevant for fluids:

  • More iterations add viscosity and stiffness to the materials mentioned above, so be careful with high values (approx. greater than 50 or 75).
  • Iterations are applied per substep: if you increase the number of substeps you will always get more viscosity/stiffness. Decrease iterations if necessary.
  • If you encounter "popping" particles with "Liquid-PBD" and fluid-object interaction then it often helps to increase "Min Iterations", e.g. to 10 or 15.

 

A few more notes:

  • "Number of Threads" specifies the number of processors/cores for the simulation.
  • You will hardly see any boost in simulation time with more than 32 threads.
  • "Use Geometry Velocity" is only relevant if your project contains animated objects*)

* In simulations with adaptive substeps RealFlow | 3ds Max works with lower precision (= less substeps) as long as the particles do not interact with objects to speed up the calculations. When objects are animated RealFlow | 3ds Max might choose the wrong number of substeps. By enabling "Use Geometry Velocity" the solver will take the interacting objects' velocities into account to determine the correct number of substeps. This way you will get proper results.

More Information

Please also take a look at the following two blog entries. They are for RealFlow Standalone, but the concept behind RealFlow and RealFlow | 3ds Max is exactly the same: