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Chapter 11 Animation Composition
it is controlled by whatever environmental physics have been assigned to it.
Environmental physics simulate gravity and wind. These settings control how
the particle interacts with the virtual environment.
For example, to create sparks, the particles might be set as orange, a size of
two, a random initial vector, and a rate of four per second. The spark may have
a lifetime of about one second. The color and opacity of the particles may be
animated from an initial
opaque
red particle to semitransparent
gray to simulate a transition from
glowing particle to smoke. In
terms of particle systems, sparks
are larger particles. Something
like smoke will have much
smaller particles, longer lifetime,
and be disbursed over a larger
area to make it realistic.
Some modeling programs have emitter settings specifically to simulate
liquids, as shown in Figure 11-14. However, liquid can be simulated using
basic particles as well. For example, the emitter can be placed at the top
of a fountain. Gravity can be set to pull the particles down toward a basin,
where they can pool together. As the basin fills with particles, some spill over
the edge. Or, to prevent spillover, set the lifetime of the particles so they are
removed before the basin fills up. To make the water appear realistic and not
just a single stream of water that follows the same path, vary the rate, direction,
and lifespan of the particles. In most software, varying settings is not totally
random. Generally, a setting contains a randomizing constraint, such as ±20
percent. This allows for a 40 percent (–20 percent to + 20 percent) variance for
all particles emitted.
CHEAT CODE: OPAQUE
Opaque means not transparent.
In other words, light cannot pass
through it.
Particle Settings Description
Initial Position How far from the emitter the particles will be created
Initial Speed How fast particles travel when created
Initial Vector What direction particles travel when created
Initial Size How big particles are when created
Initial Color What color particles are when created
Initial Opacity How transparent particles are when created
Shape What shape the particles are when created
Lifetime How long each particle will be displayed
Figure 11-15.
These are typical settings for a particle system. Depending on the software,
there may be different settings or the settings may have different names.
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