fluidEmitter

The emitter attributes in the Fluid Attributes section of the emitter Attribute Editor are described below.

For details on the standard emitter attributes, see the Dynamics guide.

Basic Emitter Attributes

Emitter Type

Select one of the following emitter types:

Omni: Sets the emitter type to an omnidirectional point emitter. Fluid properties emit in all directions.
Surface: Emits fluid properties from randomly distributed positions on or near a NURBS or polygonal surface. When you emit from an object, the emitter is a surface emitter. For information, see Display fluid container contents.
Curve: Emits fluid properties from randomly distributed positions on or near a curve.
Volume: Emits fluid properties from a closed volume. You pick the shape from the Volume Shape option.

Note
If you select Volume, make sure the emitter is bigger than one voxel.

Rate (Percent): Scales the individual emitter rate for all the fluid grids in the container, including Density, Temperature, Fuel, and Speed. The Rate (Percent) value is set as a percent with 100 as the default value.

The final emission rate of fluid grids is determined by the emitter Rate (Percent) value and the contents emission method and rate. See Fluid Attributes.
Use Per-Point Rate: When on, the emission rate of the fluid based is based on the per-particle rate value of the nParticle (or classic particle) that emits fluid. When off, the fluid emission rate is determined by the fluid emitter Rate (Percent) value. See Emit fluid properties with nParticles.
Use Per-Point Radius: When on, you can control the emission radius of the fluid based on the per-particle Radius value of the nParticle (or classic particle) that emits fluid. When off, the fluid emission radius is determined by the fluid emitter's Max Distance value. See Emit fluid properties with nParticles and Max Distance.
Cycle Emission: Cycling emission restarts the random number stream after an interval in frames, specified by the Cycle Interval attribute.

Setting “Cycle Emission” to Frame and Cycle Interval to 1 causes the random stream to restart every frame. Cycle Interval values greater than 1 can be used to generate cycles for games work.

This only resets the random stream used by the emitter. It does not reset the random number stream used by MEL, shaders, and so on. Note also that the Frame option resets at most once per frame. However, oversampling does not affect the results.
Cycle Interval: Specifies the number of frames between restarts of the random number stream. See Cycle Emission. Has no effect if Cycle Emission is set to None.
Use Distance: When on, emission distance is set using the Min Distance and Max Distance values for surface and curve emitters. In previous versions of Maya, to use Min Distance and Max Distance with surface and curve emitters, Min Distance has to be set to a value other than 0. You can now set Min Distance to 0 for surface and curve emitters.

Use Distance is ignored by volume emitters, which do not use Min Distance and Max Distance, and by omni emitters, which always use Min Distance and Max Distance.
Max Distance: Maximum distance at which new property values are created from emitter. Not used for volume emitters.
Min Distance: Minimum distance at which new property values are created from emitter. Not used for volume emitters.

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.

Emission Speed Attributes

Since Maya Fluid Effects are solved as incompressible fluids, emitting speed into a fluid container can not have the same effect as emitting speed with particles. For fluids, any speed emitted into a fluid that creates motion away from or towards a point would fight the incompressibility of the fluid. Therefore, this type of behavior is not supported by fluid emission speed.

Speed Method

Determines how velocity emission values are set in the fluid.

Add: Adds emitted velocity into the fluid as a rate each simulated step for the duration of the simulation. The amount of velocity emitted into the fluid is determined by the emitter Rate (Percent) value. See Rate (Percent).

By default, Speed Method is set to Add.
Replace: Replaces the amount of velocity in the fluid each simulated step.
No Emission: The fluid emitter does not modify the velocity of the fluid.

Inherit Velocity: Sets the amount of velocity that is inherited by the fluid from the translation velocity generated by an animated emitter. Inherited Velocity is added to the Rate (Percent) value to generate an overall emission velocity.

Inherit Velocity is calculated only when an animated emitter is present, which generates the translational velocity, or when nParticle velocity is present, such as when an nParticle object is emitting fluid.
Normal Speed: Sets the emission speed along the normals of a surface when a fluid is emitted from a surface. Normal Speed applies only when the Emitter Type is set to Surface. See Emitter Type.
Tangent Speed: Sets the emission speed along the tangents of a curve when a fluid is emitted from a curve. Tangent Speed applies only when the Emitter Type is set to Curve. See Emitter Type.
Along Axis: Sets the emission speed along the central axis of all volume emitters. The central axis is defined as positive-Y for cube and sphere volumes. Along Axis applies only when the Emitter Type is set to Volume. See Emitter Type.
Around Axis: Sets the speed around the central axis of all volume emitters. Around Axis applies only when the Emitter Type is set to Volume. See Emitter Type.
Directional Speed: Adds velocity in the direction specified by the Direction X,Y, and Z attributes. Directional Speed is applicable to all emitter types.
Direction X, Y, Z: Sets the emission speed direction relative to the emitter’s position and orientation.

Volume Emitter Attributes

Volume Shape: Indicates the shape of volume the emitter will use if the emitter is of volume type. Has an effect only if emitter type is Volume. Otherwise volume controls are disabled.
Volume Offset X, Y, Z: This is the parent attribute for the translational offset of the emission volume's center from the emitter's origin.
Volume Sweep: The arc of the volume emission. Used for sphere, cone, cylinder and torus.
Section Radius: Applies to torus volumes only. Defines the radius of a section of the torus.
Normalized Dropoff: When on, dropoff for volume emitters is fixed relative to the emitter’s scale, rather than to Worldspace. This ensures that fluid simulations remain consistent if the fluid container and emitter are scaled together. It also improves Fluid Dropoff for Cube volume emitters by using a smooth dropoff towards the volume boundaries. In previous versions of Maya, a cylindrical pattern dropoff is used with Cube volume emitters.

Object Display

For details, see the Basics guide.

Extra Attributes

For details, see the Basics guide