Create Emitter and Emit From Object Options

This sets the options when you create an emitter by selecting nParticles > Create Emitter or nParticles > Emit From Object.

See Emit nParticles

Basic Emitter Attributes

Emitter Name: The name helps you identify the emitter object in the Outliner. If you don’t enter a name, the emitter object receives a default name such as emitter1.
Solver: Specifies which Maya Nucleus solver the nParticle emitter object belongs to. Select a solver from the drop-down list (existing Maya Nucleus solvers are listed), or select Create New Solver to create a new Maya Nucleus solver for the new nParticle emitter object.

Emitter type

Omni: Sets the emitter type to an omnidirectional point emitter. Particles emit in all directions.
Directional: Sets the emitter type to a directional point emitter. Particles emit in the direction you specify with the Direction X, Y, and Z attributes.
Surface: Emits particles from randomly distributed positions on or near a NURBS or polygonal surface.
Curve: Emits particles from randomly distributed positions on or near a curve.
Volume: Emits particles from a closed volume. You pick the shape from the Volume Shape pulldown.

Rate (Particle/Sec)

Sets the average rate at which particles are emitted per second. The rate is absolute, unless you turn on Scale Rate by Object Size (see below).

Emission occurs only if your animation plays two or more consecutive frames with the emitter rate set to a positive value.

If you want to see how many particles have been emitted, select the emitted particle object and examine the Count in the General Control section of the Attribute Editor.

Note:

When you set Rate (Particle/Sec) to low values, the actual number of particles emitted may be less than the set value due to round-off errors in the emission computation. For example, if you set a rate that emits one particle per-frame, you may need to increase the Rate (Particle/Sec) by a very small amount (1.0001) to ensure that particles are emitted at specific frames.

Scale Rate by Object Size

Only available when the current Emitter Type is Surface, Curve, or Volume.

If you turn on this attribute, the size of the object emitting the particles affects the rate of particles emitted per frame. The larger the object, the greater the rate of emission. The attribute is off by default.

For surface emission, the rate is particles per centimeter of area per second. For example, a 2 cm by 2 cm plane has an area of 4 square cm. If the emission rate is 3, the plane emits roughly 12 particles each second. If you use inches or other units, Maya converts the units to centimeters to make the rate calculation.

For curve emission, the rate is particles per cm length per time unit. For example, a 4 cm curve with a rate of 3 emits roughly 12 particles per second.

If this attribute is turned off (the default), the emission rate is absolute, instead of relative to object size, which is how previous versions of Maya behave.

Use Per-Point Rates(Rate PP)

See Vary emission from different points of point emitters.

Need Parent UV

(NURBS Surface emitters only.) If you turn this on in the Emitter Options window (before you create the emitter), Maya adds parentU and parentV attributes to the particle shape and sets the needparentUV attribute to on. You can use parent UVs to drive the value of some other parameter such as color or opacity.

If you turn this on in the Attribute Editor or Channel Box (after you create the emitter). Maya sets the needParentUV attribute to on, it does not add the attributes.

Cycle Emission

Cycle Emission lets you restart the random number sequence of the emission. You can use it to create simple cycles for games work.

If you set it to Frame, the sequence is restarted after the number of frames you specify in Cycle Interval.

If you set it to None, the random number generator is not restarted.

Cycle Interval

Defines the interval in frames for restarting the random number sequence when using Cycle Emission. Only available when Frame in selected in the Cycle Emission drop-down menu.

Distance/Direction Attributes

Min Distance

Sets the minimum distance from the emitter at which emission occurs. You can enter a value of 0 or greater.

Particles are emitted randomly and uniformly between the Min Distance and Max Distance.

Max Distance

Sets the maximum distance from the emitter at which emission occurs. You can enter a value of 0 or greater, but it must be greater than Min Distance.

Direction X, Y, Z

Sets the emission direction relative to the emitter’s position and orientation. Available only for Directional, Curve, and Volume emitters.

Note: With point emitters, the emitter’s position and orientation are set by its Translate and Rotate attributes—Scale and Shear have no effect.

The original speed of particles emitted by a Directional emitter is equal to the Speed attribute of the emitter, which, by default, is 1 unit (cm) per second. The Direction X, Y and Z attributes do not affect the speed.

The original speed of particles emitted by an Omni emitter is 1 unit per second in whatever direction the particles are emitted, unless it’s been modified by the Speed Random attribute.

Spread

Sets the emission spread angle. This angle defines a conical region where the particles are emitted randomly. You can enter any value between 0 and 1. A value of 0.5 is 90 degrees, a value of 1 is 180 degrees. Available for only Directional and Curve emitters.

Basic Emission Speed Attributes

Speed

Sets a speed multiplier for the original emission speed of the emitted particles. You can enter a value of 0 or more. A value of 1 leaves the speed as is. A value of 0.5 reduces the speed by half. A value of 2 doubles the speed.

Speed doesn’t affect velocity resulting from expressions, fields, or other dynamics.

Speed Random

The Speed Random attribute lets you add randomness to your emission speeds without using expressions. If you set Speed Random to a positive value, the emitter generates random speeds for each particle. The Speed value is the mean speed; Speed Random defines the range of the speed variation.

Each particle’s speed is a random value between:

Speed - Speed Random/2 Speed + Speed Random/2

Tangent Speed

Sets the magnitude of the tangent component of emission speed for surface and curve emission (see the following figures). The default value is 0. You can enter a value of 0 or greater. Valid for surface and curve emitters only.

Normal Speed

Sets the magnitude of the normal component of emission speed for surface and curve emission (see the following figures). The default value is 1. You can enter a value of 0 or greater. Valid for surface and curve emitters only.

Volume Emitter Attributes

In the Attribute Editor and the Create Emitter option window, attributes not applicable to a volume emitter are dimmed. However, the Channel Box does not support dimming. We recommend you use the Attribute Editor instead of the Channel Box to edit volume field attributes until you become familiar with the attributes that apply to each volume shape.

Volume Shape

Specifies the shape of the volume that the particles are emitted into. Choose Cube, Sphere, Cylinder, Cone, or Torus.

Volume Offset

Offsets the emitting volume from the location of the emitter. If you rotate the emitter, you also rotate the offset direction because it operates in local space.

Volume Sweep

Defines the extent of rotation for all volumes except cubes. This can be a value between 0 and 360 degrees.

Section Radius

(Torus only) Defines the thickness of the solid portion of the torus, relative to the radius of the torus’s central ring. The radius of the central ring is determined by the emitter’s scale. If you scale the emitter, the Section Radius will maintain its proportion relative to the central ring.

Die on Emission Volume Exit

If you turn this attribute on, the emitted particles die when they exit the volume. Although this is a particle shape attribute, you can initially set it using the Emitter options window.

If you want to edit this attribute after you create the emitter, display the particle shape attributes in the Attribute Editor Volume Exit (under Emission Attributes).

Volume Speed Attributes

The Volume Speed Attributes apply only to the initial velocity of the particles. To affect particles as they move through the volume, use the Volume Axis field (see Work with volume axis fields).

Away From Center: Specifies the speed at which particles move away from the center point of cube or sphere volumes.
Away From Axis: Specifies the speed at which particles move away from the central axis of cylinder, cone, or torus volumes.
Along Axis: Specifies the speed at which particles move along the central axis of all volumes. The central axis is defined as positive-Y for cube and sphere volumes.
Around Axis: Specifies the speed at which particles move around the central axis of all volumes.
Random Direction: Adds irregularity to the direction and initial speed of the particle’s Volume Speed attributes, somewhat like Spread does for other emitter types.
Directional Speed: Adds speed in the direction specified by the Direction XYZ attributes of all volume emitters.
Scale Speed by Size: If you turn this attribute on, when you increase the size of the volume, the speed of the particles increases.
Display Speed: Turns on the display of arrows indicating speed.