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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