No doubt you will have noticed the problem of getting unwanted holes in thin or highly accelerated fluids, creating a torn look. There are ways to reduce these gaps, for example by increasing “Surface tension” or “Viscosity”. Other methods are based on RealFlow’s "Drag Force" daemon or high “Friction” settings, when there is particle-object interaction. However, these approaches all share one major disadvantage: they strongly influence the behaviour and look of a fluid. Moreover, if particle velocities become too high, even strong decelerating forces will not help anymore. This daemon is able to detect holes and fill them with particles, without increasing the emitter’s “Resolution” value. The result is a smooth stream of particles, perfectly suited for high-velocity and slow-motion simulations, or fluid-object collisions.
We have created a PDF tutorial where you can read more about how to use the "Sheeter" daemon. Please follow this link for the "Making a Paint Splash" tutorial.
The "Sheeter" daemon is fast, accurate, keeps the fluid stable and is very easy to use. You can control the entire process with just a few settings.
Max cavity size
Holes with sizes larger than this threshold value will be filled with particles. The gap between a new particle and its nearest neighbour will not be filled if the gap’s size is greater than “Max cavity size”. This parameter has no dimensions. The reason is that it has to be independent from an emitter’s “Resolution” and to avoid very small gaps which cannot be handled by the fluid solver anymore. "Max cavity size" is a sensitive parameter and the lowest possible value is 1.0. It is possible to animate this parameter.
Please note that particles might be created inside objects during the filling process. This behaviour can be diminished by setting the "Max cavity size" parameter to a lower value. Another method is to place one or more "k Volume" daemons inside the object. In future versions this limitation will be removed and RealFlow will automatically remove particles from the inside of objects.
Use relative speed
Here you can choose whether you want to take the particles’ relative speed into consideration or not. The activation of this parameter (“Yes”) unlocks the following two settings.
@ Min relative speed
Very high velocities are often responsible for unwanted holes. Gaps will only be filled if the particles’ relative speed, given in metres per second [m/s], is greater than this value.
@ Max relative speed
This parameter checks for particle velocities which are below the given value. If the measured velocity, given in metres per second [m/s], has gone below “@ Max relative speed”, the gap will be filled.
Use age
If you want to consider the particles’ age, this parameter must be set to “Yes”. Then you will also have access to the associated “@ Max age” parameter.
@ Max age
If the age of the particles around a hole is smaller than the entered value, the gap will be filled. The unit for this parameter is seconds [s].
Cavities detection ratio
There are cases where it is not wanted to fill all holes, for example to keep a fluid more vivid and diversified. This parameter is an easy means to adjust the amount of holes which will be filled: a value of 1.0 means that all gaps will be filled with particles (= 100%). With 0.5 only 50% (approx.) of the holes will be closed and 0.0 completely disables the process.