Scene : Solver

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

This is the place where the simulation preferences are defined.

 

This parameter set has three subcategories:

Threads

Number of Threads

Here you specify how many computer processors and cores you want to use with your simulations. With "Auto" activated RealFlow | 3ds Max will be using all available CPUs and cores.

Global

Time Scale

Values smaller than 1.0 will decelerate the fluid; settings greater than 1.0 have an acceleration effect. “Time scale” works as a factor: 2.0 means that the fluid will be two times faster.

Stepping Strictness

RealFlow | 3ds Max calculates how fast the fluid will move within a simulation step (aka "time step" or "substep", see below):

  • With a value of 1.0, the fluid will not move more than 1 grid cell in the current simulation step.
  • With values smaller than 1.0, the fluid can cover a longer distance within a single step – the solver is less strict.
Use Geometry Velocity

When enabled RealFlow | 3ds Max will adjust the simulation's substeps to get a correct fluid-object interaction behaviour:

  • Imagine an animated object falling into a container with calm water.

  • Here, RealFlow | 3ds Max uses very large substeps to speed up the simulation.

  • Due to these large steps the interaction between the object and the fluid is delayed.

  • With “Use Geometry Velocity” the interaction will happen in time again.

Auto Params

When enabled, RealFlow | 3ds Max applies default settings. These default values work for most projects with PDB or SPH fluids, but for other materials (granular, viscous, etc.) it is normally necessary to apply custom settings. This also applies to simulations with collision geometry involved.

Min | Max Substeps

Here you find the minimum and maximum numbers of simulation steps. Substeps play an important role for collision detection. If you see particles going through a solid object

  • decrease the object's "Cell Size" in the "Volume" tag
  • enable "Continuous Collision Detection" in the "Volume" tag
  • try do reduce the particles speed with a "Drag Force" daemon
  • if possible, make the collision object thicker.
  • If you see popping particles while the fluid settles try to increase "Min Iterations" and/or "Min Substeps".
Min | Max Iterations

These two parameters are important for the rigidity of granular, viscous, and viscoelastic materials, but they also help to avoid "popping" particles when fluids/materials interact with objects:

  • The higher the values, the more rigid the material will finally be.
  • Iterations are applied per subset, so with substeps value a materials rigidity will also increase.
  • The → "Damping" parameter influences a materials rigidity as well and the final number of substeps is substeps * iterations * damping
  • For the materials, mentioned above, a fixed number of iteration often works well, e.g. 20 | 20 or 40 | 40.
  • If you see popping particles while the fluid settles try to increase "Min Iterations" and/or "Min Substeps".
Accuracy

In most cases this value can be kept. This parameter ranges between 0.0 and 1.0. With

  • 0.0 RealFlow quickly finds a solution, but it will not be very accurate
  • 1.0 RealFlow finds a solution that is very close to the exact behaviour, but simulation time will increase.

GPU

Use GPU

If you have a compatible graphic card it can be activated here to boost the simulation.