9.0

182 RIGID BODIES
DYNAMICS
DYNAMICS
RIGID BODIES 183
Make the source object a child of the proxy object.
Set up collision detection using the proxy object instead of the source object.
The collision detection will now be processed in a fraction of the usual time. In the
case of the diagram example, 370 polygons will now be checked instead of 6500.
Elasticity
This value denes the percentage of energy that the rigid body will retain following
a collision. An Elasticity setting of 0% would cause the rigid body to halt suddenly
during the collision while a value of 100% would see the rigid body rebound without
loss of speed.
For example, in the case of a pool table, the pool balls should have an elasticity closer to
100% than to 0% since pool balls keep most of their velocity following a collision.
Static, Dynamic
When two bodies are in contact, a type of friction will exist between the bodies. If the
bodies are at rest relative to each other, the friction will be static and will resist any
motion between the two bodies, this is the friction we mostly notice during everyday
life. If the bodies are moving relative to one another, the friction will be dynamic and
try and slow the bodies by transferring the movement to heat.
Both types of friction can be simulated with Dynamics.
Static friction is always greater than dynamic friction. For example, when trying to
push a car that has broken down it is harder to get the car moving than it is to keep
it moving.
On the left, the block’s weight
component down the incline is
not great enough to overcome
‘static’ friction, so the block does
not slide.
On the right, the incline has
been increased and the block
is now sliding. Static friction
having been overcome, the
block is now being resisted
instead by the lesser force of
‘dynamic’ friction.