Fluid Attributes

Density Method

Determines how density emission values are set in the fluid. See also Controlling fluid emission.

Add

Adds emitted density into the fluid as a rate each simulated step for the duration of the simulation. The amount of density emitted into the fluid is determined by the emitter Rate (Percent) and Density/Voxel/Sec values.

By default, Density Method is set to Add.

Replace

Replaces the amount of density in the fluid each simulated step. Replace does not emit density into the fluid as a rate, but fills voxels with a total amount of density equal to the Rate (Percent) and Density/Voxel/Sec each simulated step.

No Emission

The fluid emitter does not emit density into the fluid.

Density/Voxel/Sec

Sets the average rate at which Density values are emitted into the grid voxels per second. Negative values remove Density from the grid.

Density Emission Map

Selects the 2D texture you want to map to density emission. Using a Density Emission Map, you can map a 2D texture to control emitted density.

When a surface emitter is used, emission is mapped to the surface object’s UV texture coordinates. When a volume emitter is used, the fluid’s emission is mapped to a UV projection that matches the volume’s shape. For example, Cube volumes are mapped with planar projections, while Sphere volumes are mapped with spherical projections. Density emission values are multiplied by the texture values. See also Emit fluids using emission maps.

Heat Method

Determines how heat emission values are set in the fluid. See also Controlling fluid emission.

Add

Adds emitted heat, including temperature, into the fluid as a rate each simulated step for the duration of the simulation. The amount of heat emitted into the fluid is determined by the emitter Rate (Percent) and Heat/Voxel/Sec values.

By default, Heat Method is set to Add.

Replace

Replaces the amount of heat emitted into the fluid each simulated step. Replace does not emit heat into the fluid as a rate, but fills voxels with a total amount of heat that is equal to the Rate (Percent) and Heat/Voxel/Sec each simulated step.

No Emission

The fluid emitter does not emit heat into the fluid.

Heat/Voxel/Sec

Sets the average rate at which Temperature values are emitted into the grid voxels per second. Negative values remove heat from the grid.

Heat Emission Map

Selects the 2D texture you want to map to heat emission. Using a Heat Emission Map, you can map a 2D texture to control emitted heat, which includes temperature.

When a surface emitter is used, emission is mapped to the surface object’s UV texture coordinates. When a volume emitter is used, the fluid’s emission is mapped to a UV projection that matches the volume’s shape. For example, Cube volumes are mapped with planar projections, while Sphere volumes are mapped with spherical projections. Temperature emission values are multiplied by the texture values. See also Emit fluids using emission maps.

Fuel Method

Determines how fuel emission values are set in the fluid. See also Controlling fluid emission.

Add

Adds emitted fuel into the fluid as a rate each simulated step for the duration of the simulation. The amount of fuel emitted into the fluid is determined by the emitter Rate (Percent) and Fuel/Voxel/Sec values.

By default, Fuel Method is set to Add.

Replace

Replaces the amount of fuel emitted into the fluid each simulated step. Replace does not emit fuel into the fluid as a rate, but fills voxels with a total amount of fuel that is equal to the Rate (Percent) and Fuel/Voxel/Sec each simulated step.

No Emission

The fluid emitter does not emit fuel into the fluid.

Fuel/Voxel/Sec

Sets the average rate at which Fuel values are emitted into the grid voxels per second. Negative values remove Fuel from the grid.

Fuel Emission Map

Selects the 2D texture you want to map to fuel emission. Using a Fuel Emission Map, you can map a 2D texture to control emitted fuel.

When a surface emitter is used, emission is mapped to the surface object’s UV texture coordinates. When a volume emitter is used, the fluid’s emission is mapped to a UV projection that matches the volume’s shape. For example, Cube volumes are mapped with planar projections, while Sphere volumes are mapped with spherical projections. Fuel emission values are multiplied by the texture values. See also Emit fluids using emission maps.

Fluid Dropoff

Sets the dropoff value for fluid emission. For Volume emitters the dropoff specifies how much the emission drops off as you move away from the volume axis (dependent on the volume shape). For Omni, Surface, and Curve emitters the drop off is based on the emission point and radiates out from Min Distance to Max Distance.

Emit Fluid Color

Turn this option on to emit color into the fluid color grid. The grid must be dynamic.

Fluid Color

Click the color swatch and select the emitted fluid color from the Color Chooser. This color is used only when Emit Fluid Color is turned on.

Note:

The default color of a fluid grid is grey and when this color is emitted it blends into other instances of grey, which can create grey fringes. To resolve this, set the initial state of the fluid color grid to a preferred color. You can also use two emitters: one for density emission and a larger one with no dropoff that only emits color.

Motion Streak

When on, fluid streaks from fast moving fluid emitters are smoothed to appear as a continuous streak rather than a series of emission stamps. Motion Streak is useful for creating continuous fluid in effects that use fast moving emitters such as missile trails and rocket exhaust.

Note:

For Omni, Surface, and Curve emitters, Motion Streak uses a smooth, anti-aliased emission method (instead of jitter) that uses the set Max Distance value.

Jitter

Turn this option on to provide better anti-aliasing around the edges of emitting volumes. Some effects, such as oceans and pond wakes appear better with this option turned off.

Fluid Emission Turbulence

Turbulence Type

Select the type of turbulence to apply to fluid emission.

Gradient

Applies turbulence that ranges smoothly through space.

Random

Applies random turbulence.

Turbulence

The intensity of a force simulating a turbulent wind that evolves over time.

Turbulence Speed

The rate of change of the turbulence over time. The turbulence loops seamlessly every 1.0/Turbulence Speed seconds. To animate this rate attach a new time node to the time input and animate the time value on the time node.

Turbulence Freq

Controls how many repeats of the turbulence function fit inside the bounding volume of the emitter. Low values create a very smooth turbulence.

Turbulence Offset

Use this option to translate the turbulence within the volume. Animating it can simulate blowing turbulent wind.

Detail Turbulence

The relative intensity of a second higher frequency turbulence. This can be used to create fine features in large scale flows. Both the speed and the frequency on this second turbulence are higher than the primary turbulence. When the Detail Turbulence is non-zero the simulation may run a bit slower, due to the computation of a second turbulence.