Graphics Programs Reference
In-Depth Information
in the Attribute Editor is the emitter1 node that belongs to the
particle's emitter. This makes it easier to toggle back and forth to
adjust emitter and particle settings.
The Lifespan Attributes
When any particle is created, or born, you can give it a
lifespan
, which
allows the particle to die when it reaches a certain point in time. Giving
particles a lifespan is a good idea for a variety of reasons. As you'll see
with the steaming locomotive later in the chapter, a particle that has
a lifespan can change over that lifespan. For example, a particle may
start out as white and fade away at the end of its life. A lifespan also
helps keep the total number of particles in a scene to a minimum,
which helps the scene run more efficiently.
You use the Lifespan mode to select the type of lifespan for the
nParticle:
Live Forever
The particles in the scene can exist indefinitely.
Constant
All particles die when their Lifespan value is reached.
Lifespan is measured in seconds, so upon emission, a particle with
a Lifespan of 1.0 will exist for 30 frames (in a scene set up at 30fps)
before it disappears.
Random Range
This type sets a lifespan in Constant mode but assigns
a range value via the Lifespan Random attribute to allow some par-
ticles to live longer than others for a more natural effect.
LifespanPP Only
This mode is used in conjunction with expres-
sions that are programmed into the particle with Maya Embedded
Language (MEL). Expressions are an advanced Maya concept and
aren't used in this topic.
Figure 12.20
nParticle attributes
The Shading Attributes
The Shading attributes determine how your particles look and how they will render. Two
types of particle rendering are used in Maya: software and hardware.
Hardware particles
are typically rendered out separately from anything else in the scene and are then com-
posited with the rest of the scene. Because of this compound workflow for hardware par-
ticles, this topic will introduce you to a software particle called
Cloud.
Cloud, like other
software particles
, can be rendered with the rest of a scene through the software renderer.
With your particles selected, open the Attribute Editor. In the Shading section, you'll
find the Particle Render Type drop-down menu (see Figure 12.21).
