Introducing Maya® 2008

To create a particle disk cache, switch to the Dynamics menu and choose Solvers

➔

Cre-

ate Particle Disk Cache. Maya will run the simulation according to the Timeline and save

the position of all the particle systems in the scene to cache files in your current project’s

particle folder. You can then play your animation back and forth and the particles will run

properly.

If you make any dynamics changes to the particles, such as emission rate or speed, you will

need to detach the cache file from the scene for the changes to take effect. Choose Solvers

➔

Edit Oversampling or Cache Settings, and uncheck the Use Particle Disk Cache check box.

Now that you understand the basics of particle dynamics, it’s time to see for yourself

how they work.

Animating a Particle Effect: Locomotive Steam

You will create a spray of steam puffing out of the steam pump on the side of the locomo-

tive that drives the wheels on the model you started creating in Chapter 4, “Modeling with

Polygons,” and Chapter 5, “Modeling with NURBS.” We’ll use the more detailed locomo-

tive from Chapter 8, “Introduction to Animation,” and Chapter 9, “Further Animation

Practices.”

Emitting the Particles

The first step is to create an emitter to spray from the steam pump and to set up the

motion and behavior of the particles:

1. In the Dynamics menu, choose Particles

➔

Create Emitter

➔

❒. Set Emitter Type to

Directional and click Create. Place the emitter at the end of the pump, as shown in

Figure 12.25.

Figure 12.25

Place the emitter at

the end of the

pump.

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2. To set up the emission in the proper direction, adjust the attributes of the emitter. In

the Distance/Direction Attributes section, set Direction Y to 0, Direction X to 0, and

Direction Z to 1. This emits the particles straight out of the pump over that first large

wheel and toward the back of the engine.

3. Play back your scene. You’ll see particles emit in a straight line from the engine, as

shown in Figure 12.26.

You can load the file

Locomotive_Steam_v1.ma from the Locomotive project on the

CD to check your work.

4. To change the particle emission to more of a spray, adjust the Spread attribute for the

emitter. Click the emitter1 tab in the particle’s Attribute Editor (or select the emitter

to focus the Attribute Editor on it instead), and change Spread from 0 to 0.25.

Figure 12.27 shows the new spray.

Figure 12.27

The emitter’s Spread attribute widens the spray

of particles.

Figure 12.26

Particles emit in a straight line from the pump.

The Spread attribute sets the cone angle for a directional emission. A value of 0 results in a

thin line of particles. A value of 1 emits particles in a 180-degree arc.

The Direction attributes are relative. Entering a value of 1 for Direction X and a value of 2 for

Direction Y will make the particles spray at twice the height (Y) of their lateral distance (X).

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