Scene Settings

Owned by thomas (Unlicensed)
Last updated: 26 Jul, 2016
2 min read

In many cases the pre-adjusted scene and simulation settings do not have to be altered, but there are situations where it is necessary to make changes. The scene settings are located under the "Scene" tree's "Solver" tab. A complete parameter reference can be found under → Parameter Reference > Scene > Solver. Here, the most important terms and parameters will be explained:

Number of Threads

This value determines how many CPU cores and threads will be used by RealFlow | Cinema 4D. If your machine supports hyper threading the number of threads is higher than the actual number of cores.

In simulations with just a few hundred particles it is often better to decrease "Number of Threads", e.g. from 16 to 8, or even 4. You will also notice that there is hardly any speed boost with more than 32 threads. The reason is that computer performance does not scale linearly, and RealFlow | Cinema 4D also needs a certain amount of time for splitting up the simulation into separate threads.

 

Substeps

In simulations, time is subdivided into chunks and such a chunk represents a substep, also known as time step or simulation step:

  • The more substeps, the higher the simulation's accuracy, but at the cost of longer simulation times.
  • When a simulation produces obviously wrong results, e.g. exploding particles, you should consider increasing the number of substeps.
  • By default, RealFlow | Cinema 4D uses so-called adaptive substeps. This means that the actual amount of steps is calculated by the fluid engine based your "MIN Substeps" and "MAX Substeps" values.

 

 

The question is how to find a good balance between simulation speed and accuracy? As always, this depends on your simulation and the used → fluid type, but there are a few rules:

  • With fast moving fluids and object interaction, "MAX Substeps" should be increased.
  • When particles misbehave, "MIN Substeps" and "MAX Substeps" should be increased.
  • With pure "Liquid - SPH" particle simulations, "MAX Substeps" can be decreased (75-100 are often enough for → "Liquid - SPH").
  • With high viscosity simulations, "MIN Substeps" and "MAX Substeps" should be equal (start with 20 | 20 for → "Liquid - PBD" and 200 | 200 for → "Liquid - SPH").