Bifröst Kill Field attributes

The attributes on the bifrostKillFieldContainer node can be used to delete Bifröst liquid, foam, or aero particles based on various criteria. See Delete particles with kill fields.

Container Attributes

Enable

Enables evaluation of the entire container node.

Evaluation Type

Controls how the node is evaluated. Normally, this should not be changed.

Simulation

The node gets evaluated based on the previous frame.

Property

The node is used only to set values used by other nodes.

Mesh Property

The node is used to set values on polygon mesh objects, such as emitters, colliders, and other meshes used in a simulation.

Per Frame

The node is evaluated every frame, but does not depend on the previous frame. This mode can be used for animation or reading cache files.

Kill Field Properties

Boundary

When used by itself, Boundary immediately deletes particles within the volume defined by the Boundary Controls. When used in conjunction with one or both of LifeSpan and Droplets, it restricts their effect to particles within that volume. For example, if you use LifeSpan, you can make older particles begin to die only when they either leave or enter a specific region.

When Boundary is off, LifeSpan and Droplets affect particles everywhere.

LifeSpan

Deletes particles based on their age (time since emission). For this option to work, you must enable Age in the Optional Channels attribute group of the liquid properties. This mode is supported for liquid and foam only, and may produce unexpected results with aero.

Droplets

Deletes particles based on the value of their Droplet channel (see Work with Bifröst droplets). This mode is supported for liquid only, and may produce unexpected results with foam or aero.

Boundary Controls

Controls the shape of the implicit boundary when Enable Boundary is on. Scale, rotate, and translate the node in the scene to define the affected volume.

Boundary Shape

Select a shape.

The InMesh option uses the connected polygon mesh, if one exists.

Section Radius

The "tube" radius, in the case of a torus shape.

Boundary Falloff

Uses a falloff curve to modify each particle's probability of dying. A particle's base probability of dying is determined by one or both of the settings in the Lifespan and Droplets attribute groups. The Boundary Falloff controls the exponent of the falloff curve based on each particle's position, so for example:

• 0.0 gives no falloff. The base probability of dying is unchanged throughout the field's volume of effect.
• 1.0 gives a linear falloff from the base probability at the center of the field to 0.0 outside the boundary.
• 2.0 gives an inverse-square falloff from the base probability at the center to 0.0 outside the boundary.

If Invert is on, the falloff is reversed so that the full effect of the base probability is applied everywhere outside the boundary. Within the boundary, the effect falls off to nothing at the center.

Invert

Affects particles inside the boundary when off, or outside the boundary when on.

Protect Inside

When Invert is on, this option prevents particles inside the field's boundary from being deleted by other fields. This can be useful when other fields overlap with this one.

Enable Max Depth, Max Depth

Restricts the effect of the field to a layer of the specified depth below the surface of the fluid volume. Activate this option to delete particles from the outside in without creating holes in the fluid interior.

Note that this option does not require Enable Boundary to be activated.

Lifespan

Controls how particles die when Mode is set to LifeSpan. Particles that are younger than Min Age are never killed, and particles that are older than Max Age are always killed. Between Min Age and Max Age, particles have a random chance of dying, with older particles being more likely to die.

Set both of these attributes to the same value if you want all particles to die at the same age.

Droplets

Controls how particles die when Mode is set to Droplets. Particles with a Droplet channel value between Min Droplet Value and Max Droplet Value die randomly, and all particles with a Droplet channel value above Max Droplet Value are killed.