Introducing Maya® 2008

With this methodology, you could bake out the animation of any simulation, from

dynamics (as we just did) to constraints and some scripts. The curve simplification works

with good old-fashioned keyframed curves as well, so if you inherit a scene from another

animator and need to simplify the curves, do it just as we did here.

Particle Dynamics

Like rigid body objects, particles are moved dynamically using collisions and fields. In

short, a particle is a point in space that is given renderable properties; that is, it can render

out. When particles are used en masse, they can create effects such as smoke, a swarm of

insects, fireworks, and so on. Although particles can be an advanced and involved aspect

of Maya, it is important to have some exposure to them as you begin to learn Maya.

Much of what you learned about rigid body dynamics transfers to particles. However, it

is important to think of particle animation as manipulating a larger system rather than as

controlling every single particle in the simulation. You control fields and dynamic attrib-

utes to govern the motion of the system as a whole.

For example, with the pool table you control the motion of the cue ball and let Maya

dynamics calculate the motion of the other balls after they collide. Each ball is a distinct

part of the scene and renders out as a distinct object in the frame. Particles are most often

used together in large numbers so that the entirety is rendered out to create an effect. To

control a particle system, you’ll create an emitter and define fields and attributes that con-

trol the particles’ movement.

Figure 12.15

Creation options for

a Particle emitter

Emitting Particles

Typical work flow for creating a particle

effect in Maya breaks into two parts: motion

and rendering. First, you create and define

the behavior of particles through emission.

An emitter is a Maya object that creates the

particles themselves. After creating fields

and adjusting particle behavior within a

dynamic simulation, much as you would do

with rigid body motion, you give the parti-

cles renderable qualities to define how they

look. This second aspect of the workflow

defines how the particles “come together” to

create the desired effect, such as steam. You

will make a steaming locomotive pump later

in this chapter.

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To create a particle system, follow these steps:

1. Make sure you are in the Dynamics menu, and then choose Particles

➔

Create

Emitter

➔

❒. The Option box gives you various creation options for the Particle emit-

ter, as shown in Figure 12.15.

The default settings will create an Omni emitter with a rate of 100 particles per sec-

ond and a speed of 1.0. Click Create. A small round object (the emitter) will appear

at the origin.

2. Click the Play button to play the scene. As with rigid body dynamics, you must also

play back the scene using the Play Every Frame option. You cannot scrub or reverse

play particles unless you create a cache file. You will learn how to create a particle disk

cache later in this chapter. But for the most part, particles need to be played back to

run properly.

You will notice a mass of small dots stream out of the emitter in all directions (see Fig-

ure 12.16). These are the particles themselves.

Emitter Attributes

You can control how particles are created and behave by changing the type of emitter and

adjusting its attributes:

Omni Emits particles in all directions.

Directional Emits a spray of particles in a specific direction, as shown in Figure 12.17.

Figure 12.16

An Omni emitter

emits a swarm of

little particles in all

directions.

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Volume Emits particles from within a specified volume, as in Figure 12.18. The volume

can be a cube, a sphere, a cylinder, a cone, or a torus. By default, the particles can leave the

perimeter of the volume.

After you create an emitter, its attributes govern how the particles are released into the

scene. Every emitter has the following attributes to control the emission:

Rate Governs how many particles are emitted per second.

Speed Specifies how fast the particles move out from the emitter.

Figure 12.18

Particles emit from

anywhere inside the

emitter’s volume.

Figure 12.17

Particles sprayed in

a specific direction

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