Bifröst Liquid EmitterProps, EmissionRegionProps attributes

The Bifröst liquid emitterProps control the emission from mesh objects that share this property. See Work with Bifröst emitters.

The emissionregionProps share many of the same attributes plus Death Age, but apply to meshes used as emission regions in guided liquid simulations. See Guide Bifröst liquid with a planar mesh in defined regions.

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.

Properties

Enable: Enables liquid emission from the associated emitters.
Continuous Emission: Refills voxels that become empty with more particles. Keep this on for liquid sources like spouts and jets, or turn it off for a pool or single drop of liquid.

Conversion

Controls how the object's volume is voxelized, as well as how properties such as velocity are transferred .

Mode

Controls how the object is voxelized:

Solid creates a solid volume including the mesh interior. The mesh should be both manifold and watertight.
Shell create a thin shell around the mesh surface. In this mode, Thickness should typically be 1.0 or more.
Solid (Robust) is an alternative to Solid that usually gives better results for volumes with fine detail, openings leading to cavities, or non-watertight surfaces. However, it does not handle fluids inside completely enclosed regions.

Coarsen Interior

Saves memory by performing additional coarsening of the voxels inside the volume when Mode is Solid (Robust), especially with self-intersecting meshes.

Offset Surface Distance

The distance in voxel widths used to close (dilate and then erode) the solid voxels when Mode is Solid (Robust). The internal minimum is 1.0 so only values greater than that have an effect. High values can create artifacts.

Thickness Units

Whether Thickness is in Voxels or World Space units. When set to Voxels, the effective thickness depends on the Master Voxel Size of the simulation.

Thickness

The amount to thicken the mesh. For solid shapes that are already quite thick, you can use 0.0 for a precise boundary or even negative values to shrink along the surface normals. For thinner volumes and shells, you should use larger values to prevent holes.

Note that thickness will round off sharp corners.

Voxel Scale

Scaling factor for the Master Voxel Size used to initially voxelize meshes that share this property. See Control the voxel resolution of a Bifröst simulation.

Velocity Scale (EmitterProps only)

Controls the proportion of velocity that is inherited from the emitters' animated transformation and deformation by the fluid at the time of emission in each of the world X, Y, and Z axes.

At the default value of 1.0, the fluid is emitted with the same velocity as its emitter. As a result, the fluid tends to follow the mesh closely at first.
At 0.0, the fluid inherits no initial velocity from its emitter. As a result, it does not follow its emitter at all.
Between 0.0 and 1.0, the fluid inherits only a portion of its emitter's velocity. As a result, it partially follows its emitter but lags behind.
Above 1.0, the fluid is emitted with a higher velocity than its emitter. As a result, it shoots ahead of its emitter's motion.
Below 0.0, the fluid is emitted in the opposite direction from its emitter's motion.

Additional Velocity controls (EmitterProps only)

These attributes work together to apply an optional, extra velocity that is independent of the animation of the emitting meshes. For example, you can set these on an emitter to shoot fluid out as if from the nozzle of a hose even if the mesh is not animated.

Enable Additional Velocity: Adds extra velocity to any existing velocity from other sources (such as that inherited from the emitter's animation).
Additional Velocity Mult: A multiplier that scales Additional Velocity uniformly in all axes.
Additional Velocity: The base velocity to add in world coordinates.

Boundary Controls

Limits the effect of the associated mesh objects to their intersection with an implicit shape. See Limit the volume of a mesh's effect using boundary controls.

Enable Boundary: Activates the boundary controls.
Boundary Shape: Selects the shape of the boundary volume.
Invert: Restricts the effect of the mesh to the exterior instead of the interior of the boundary volume.

Emission

Death Age (emission region only)

Length of time in seconds that a particle can be outside its emission region before it is deleted.

Blend With Guide (emission region only)

The blend weight of the input velocities from the guide. This helps to provide a smooth transition from the simulation to the guide.

At 1.0, the particle positions at the boundary of the emission region depend only on the guiding velocities, with a linear blend to the velocities from the simulation in the interior of the region. At 0.0, the velocities from the simulation are used throughout the entire region.

Physical Attributes

Density

The physical density of the fluid, by default in kg/m³. A value of 1000 corresponds to the density of water, assuming that 1 grid unit = 1 meter when Maya's Linear working unit is left at the default value of 1 cm. Changing this value will not have an effect on the simulation unless other options such as Viscosity or Surface Tension are enabled, or unless different emitters use different densities.

Note: Density does not affect the rate at which particles are emitted.

Expansion Rate

Expands or contracts the liquid within the emitter. Positive values push particles out of the emitter in all directions, while negative values pull particles in, and a value of 0.0 neither pushes nor pulls.

For example, to fill a container from the bottom, you can use a positive Expansion Rate to push particles out of the emitter, in combination with Continuous Emission to refill the emitter as it empties.

Mathematically, this value defines the divergence that Bifröst tries to maintain in each voxel of the emitter's velocity field. A value of 0.0 corresponds to an incompressible fluid.

Stickiness

Strength: The amount that the fluid from this emitter adheres to nearby colliders.
Bandwidth: How close the fluid from this emitter needs to be to a collider for the stickiness to affect it, in world-space units.

UV Projection

Defines UV coordinates that get advected with the particles. Select a Projection, and then click Tool to activate a manipulator to adjust the projection.