Splash & Foam - Splash Creation

This panel provides a wide variety to control and manage the emission of splash particles from the core fluid. The various threshold parameters (e.g. “Curvature threshold”) are of particular interest, because they will finally trigger the emission of splash particles.

RealFlow also provides an easy-to-use method of previewing the areas where the splash emission occurs: once you have finished the field calculation you will be able to see these areas. Simply choose:

Grid fluid domain node > Node Params > Display > Property > Splash/Foam preview

and adjust the now unlocked threshold values. These parameters are exactly the same as in the “Splash” emitter's “Splash Creation” panel. Once you have found a working combination, all you have to do is to transfer the values from the domain to the emitter and start the simulation. This is a very fast way of getting an idea of where splashes will occur, but without having to run the entire splash pass. For a complete description of this workflow, please visit this page.

Emission rate

When you take a look at the emitter's “Particles” panel you will see that it lacks a “Resolution” parameter, because “Emission rate” is used to create particles. The value you enter here is the number of particles which are created per second per cubic metre.

Angle threshold

This parameter takes the fluid surface's main direction of motion into account. The particles themselves also have an individual direction of motion caused by their velocity. RealFlow measures the angle between these two directions, and when the angle is between 0° and the given threshold splash particles will be added. The value is measured in degrees [deg].

Curvature threshold

You can use the fluid's curvature to trigger the generation of splash particles. This value represents the minimum curvature for the creation of splashes. Curvature can also be seen as the fluid surface's “roundness”. With higher values, the fluid's borders/surface must have a stronger curvature to start the emission of splashes. With small values, the parameter is less sensitive and creates particles even in areas with low curvature. This parameter is dimensionless and any value greater than or equal to 0 can be used.

Speed threshold

It is also possible to use the underlying grid fluid speed for the splash creation process. If the fluid's velocity is below the adjusted threshold, no new splashes will be generated. “Speed threshold” is very easy and effective way to reduce the amount of splash particles. The parameter's unit is metres per second [m/s].

Vorticity threshold

"Vorticity" is a very interesting and important value that represents the strength of vortices that will arise in turbulent mediums like fluids or smoke. Using vorticity as a trigger can create very nice, natural results. This property can even be used when the Hybrido domain's “Vorticity” channel has not been activated.

Neighbors threshold

A value of 0 disables this threshold parameter. Other values determine the minimum number of neighbour particles the currently observed grid fluid particle must have in order to emit splashes.

Position variation

This parameter can also be used to effectively increase/decrease the number of splash particles, because Hybrido creates splashes within a certain radius (= the parameter's value) around the current grid fluid particle. If the value is high, you will see clouds around the particles. In this case you should choose a smaller value. The parameter is measured in metres [m].

Angle variation

Hybrido adds splashes within the given angle. Large values can create a torn and randomized look which is not always desired. With smaller settings it is possible to keep the splashes closer together. The parameter uses degrees [deg].

Velocity variation

The last setting for avoiding regular patterns randomly modifies the original particle velocity, and uses the entered value as the maximum variation. “Velocity variation” works well for core fluids with a rather uniform distribution of velocities and makes the splashes more vivid. The parameter's unit is metres per second [m/s].

Secondary splash

Sometimes, grid fluid simulations do not have enough splash particles, especially at lower resolutions. To generate more splashes, this option can be activated and new particles will be created when a splash particle enters the core fluid. When this option is active, the following two parameters will be unlocked.

@ Bounce

This parameter is interesting for very strong splashes, for example from huge breaking waves, because you can adjust how much the splash particles will bounce against the grid fluid.

@ Radius threshold

Standard particles always have a certain radius that is internally calculated by RealFlow. The radius represents the fluid's drop size and can be used for various applications. One of these applications is the creation of secondary splash particles above a certain radius.