HyFLIP - Cell Size

Owned by thomas (Unlicensed)
Last updated: 24 Nov, 2015
3 min read

One of the most important parameters is “Cell size”, because it occurs in so many places: the Hybrido domain node, all objects, and even the “Splash” emitter has a “Cell size” parameter when its particle type is set to “Hybrido”. Here are answers to some of the most common questions about “Cell size".

What is the “Cell size” parameter?
  • HyFLIP simulations work with grids and these grids are made of cells with a certain size.
  • The value represents the smallest possible length of a cell's edges.
  • With Cell size = 0.3, the smallest cell will be 0.3 m x 0.3 m x 0.3 m = 0.027 m3.
How does “Cell size” affect a simulation?
  • With smaller cell sizes you create more cells and therefore the number of particles will be increased as well. This also results in longer simulation times.
  • Smaller cells improve → fluid-object interaction.
Why do objects have a “Cell size” parameter?
  • HyFLIP simulations are based on cells and this affects objects as well.
Does an object's “Cell size” influence RealFlow's other simulation engines (rigid bodies, RealWave etc)?

  • Partially. This parameter is relevant for HyFLIP and Dyverso simulations.

Does an object's “Cell size” influence HySPH simulations, e.g. splash or foam?
  • Only indirectly, because the amount of core fluid particles is responsible for the creation of HySPH elements.
  • “Splash” and “Splash and Foam” particles can be simulated with the Hybrido solver. In this case, “Cell size” is relevant again.
  • “Mist” is a volumetric node and always uses cells for storing the mist clouds, but here “Cell size” is adjusted independently from other nodes.
It's annoying to change the “Cell size” parameters of dozens of objects. Isn't there a faster way?

 

 

  • Of course! Click on the icon shown above to open the “Scale Options” window.
  • “Cell size scale” will be applied as a factor to all of the scene's grid-based nodes.
  • If your objects and domains use different values they will be changed accordingly.
I have decreased my object's “Cell size” too a very small value, but it's still leaking. Why?
  • Please take a look at → “HyFLIP - Fluid-Object Interaction” to learn how to optimize your objects.
  • If the object's “Cell size” value is smaller than the one from the domain then you will not see any improvement.
  • Does the object contain very thin structures? The minimum thickness that can be recognized by Hybrido is equal to the domain's “Cell size” value.
  • If the fluid is very fast it is also possible that particles will simply go through an object. You can make your object thicker, and/or increase the number of → substeps.
Is there a way to bypass “Cell size”?

  • No, because cells are a fundamental part of the Hybrido technology.

Is it possible to work with different “Cell size” values for domain and objects?
  • Yes, but please bear in mind that the domain's “Cell size” parameter is always the reference.
  • It has absolutely no effect when an object's value is smaller than the domain's “Cell size”.
How does “Cell size” influence simulation times?
  • A higher number of cells results in longer simulation times.
  • The effective simulation time depends on many other parameters, e.g. → “MIN | MAX substeps”, → “Particle sampling”, → “Creation mode”, and interacting objects.
  • If the scene contains complex objects with small “Cell size” it takes longer to prepare and start the simulation.
  • More cells allocate more memory and simulation files will be bigger.