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Chapter 43: Simulating Physics-Based Motion with reactor
FIGURE 43.4
The Property Editor can set the physical properties for geometric objects included in the scene.

Mass, friction, and elasticity
The Mass property defines how heavy the object is. For example, a bowling ball has a higher mass value
than a Ping-Pong ball. The Elasticity value defines how springy the object is; a tennis ball is more elastic
than a marble. The Friction value defines how resistant the object is to rolling or sliding along the floor. For
example, a brick has a higher friction value than an ice cube.

Tip
A rigid body with a Mass value of 0 is left out of all calculations and remains stuck in the simulation. n
The Property Editor also includes several other options. The Inactive option removes the object from the
simulation calculations. The Disable All Collisions option causes the object to not collide with other objects.
The Unyielding option makes the object immovable and is good to use for floor and wall objects, and the
Phantom option makes objects so they have no impact on other objects in the scene.
The Shell value defines an additional radius that surrounds convex shapes and is used for collision detec-
tion. If you specify a shell value, the simulation runs much more quickly, and the likelihood that objects
will interpenetrate each other is much less. The Penetration value is the amount of penetration that is
allowed between objects. By providing a non-zero value, the simulation can be solved much more quickly.
The Quality settings let you set how important the object’s motion is to the animation. The options include
Debris, for objects of low importance; Moving, for objects of medium importance; Critical, for objects that
should never penetrate other objects; and Bullet, for objects that move rapidly. The Shell, Penetration, and
Quality values work only with the version 3 reactor engine.

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