Daemons - Sheeter

Owned by thomas (Unlicensed)
Last updated: 11 Mar, 2016
4 min read

The “Sheeter” daemon's main purpose is to detect holes in particle fluids and fill them, but 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:

  • Please note that simulations where the "Sheeter" daemon is used cannot be → retimed.



 

Min cavity size

Holes with a radius greater than the given value will not be filled. This parameter accepts positive values and is dimensionless. The daemon does have its limits, and there are situations where it is impossible to fill all holes. This, for example, can be the case when the fluid particles are very fast or when the holes are large. Good values range between 1.0 and 3.5, but this strongly depends on your simulation.

Use velocity alignment

This feature improves the quality of simulation with thin sheets of fluids, e.g. with the “Linear” emitter. Another situation is when particles collide with objects. In the object's corners you can often see accumulations of particles. To avoid this, increase the “@ alignment threshold” angle.

@ alignment threshold

Particle A is moving at a certain velocity which also determines its direction – this is the motion vector. Another vector points in the direction of particle B. The angle (α) between both vectors is compared against “@ alignment threshold”. If this angle is smaller than the given parameter value then a new particle will be created between A and B. The following illustration explains this concept:




Use relative speed

By taking the particles' speed into account you are able to do a lot of interesting things:

  • Restrict the particle creation process to particles within the given range between “@ min |max relative speed”. This way you can create fast moving, trailing drops which are not linked to the main body of fluid.
  • If a particle is very fast compared to its neighbour then you might see very long and thin tendrils. By defining a “@ max relative speed” value you are able to break the link between these particles.
  • Another situation where it is helpful to define speed thresholds is when one particle is moving, while its neighbour is colliding and suddenly stopping. Normally, you do not want the “Sheeter” to fill the gap between this particles. When the moving particle's speed is greater than “@ max relative speed” the gap will not be filled.

We recommend taking a look at the emitter's → “Statistics” panel to monitor the fluid's minimum and maximum velocity. These values will help to find working “@ min/max relative speed” thresholds.

@ min relative speed

Only particles with a velocity greater than the given value will be taken into account for the hole-filling process. Please also read the descriptions under “Use relative speed”. This parameter is measured in metres per second.

@ max relative speed

Only particles with a velocity smaller than the given value will be taken into account for the hole-filling process. Please also read the descriptions under “Use relative speed”. This parameter is measured in metres per second.

Use age

This feature is used to break up the fluid at a certain point in time. Switch this option to “Yes” to make use of the associated “@ max age” value.

@ max age

When the “Use age” option is active you can specify an age in seconds. Only particles with an age smaller than the given value will be used for the hole-filling process.

Cavities detection ratio

With 1.0 all of the detected holes will be filled – this corresponds with 100%. A value of 0 means that the hole-filling process is disabled. This can be interesting if you only want to create tendrils, but do not want to fill the space between the trailing particle and the main body of fluid.

Create tendrils

This option allows you to pull out individual particles from the main body of fluid and create strings. The number of tendrils is controlled with “@ count”.

@ count

Here you can specify how many tendril particles the daemon should create. The actual number of tendrils strongly depends on the fluid's characteristics and can be smaller than the given value.

@ creation time

You can determine at which point in time the “Sheeter” daemon should create the tendrils. This value is measured in seconds.

@ acting time

Here you define how many seconds the force, adjusted under “@ strength”, should act on the tendril particles. Higher settings create longer fibres.

@ strength

This is the force that acts on the tendril particles. Highly accelerated particles might leave the “Sheeter” daemon's search radius. and the fluid cloud cannot be filled anymore. This results in isolated particles or droplets. If you want to remove isolated particles please consider using “k Speed”, “k Isolated”, or ”k Volume” daemons.