9.5.2

386 • CHAPTER 7
OBJECTS MENU • PARTICLES • 387
A Deector modier deects particles. A realistically animated billiard table could quite easily be
created with just ve deectors (one for the surface plus four cushions). The emitter creates just one
particle (a sphere for the ball) that never leaves the table, rebounding off the cushions.
Beware of using fast moving particles with deectors. Consider a simple particle moving at a high
velocity of 200 units per frame. In the rst frame it is 100 units in front of the deector. However, in
the next frame it has moved to 100 units behind the deector. The deector algorithm simply does not
see the particle and has no chance to inuence it. This is a problem common to all particle simulations
currently available.
The use of the Bake Particles command may help here (Object manager: Objects > Bake Particles).
In the Bake Particles dialog, dene a higher Samples Per Frame, such as 10. This will ensure that the
entire animation, and in particular those frames involving particle calculations, are rendered with a
higher time rate (in this case, it would be 10 times higher). The deector then has a chance of seeing,
and thus inuencing, the particle.
Attribute manager settings
Object Properties
Elasticity
Indicates how bouncy the deectors should be, i.e. the degree of rebound. With a value of 100%, the
exit angle is the same as the entry angle. The smaller the elasticity value, the more the particle’s energy
is absorbed by the deector and the more the motion proceeds along the direction of the deector.
Split Beam
If this option is enabled, the deector divides the particle stream. Some of the particles will be
deected, while the remaining particles ignore the deector and pass through unhindered.
Size X, Size Y
Denes the size of the Deector modier in the X and Y directions.