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Maya has two kinds of rigid bodies—active and passive.
An active rigid body is animated by dynamics—fields, collisions, and
springs—not by keys.
Because the ball and planks are all active rigid bodies, gravity pushes
it down and it rebounds after colliding with the planks.
A passive rigid body can have active rigid bodies collide with it. You
can key its Translate and Rotate attributes, but dynamics have no effect
on it.
In the previous steps, all the planks were active rigid bodies and
reacted to the collision of the ball. In the following steps, you'll
change the bottom plank to be a passive rigid body so the ball bounces
off the plank but the plank doesn't react to the collision.
To change an active rigid body to a passive rigid body
Select pCube1 and display the Attribute Editor.
Click the rigidBody1 tab to display the rigid body attributes.
In the Rigid Body Attributes section, turn off Active to make pCube1 a
passive rigid body. Hide the Attribute Editor.
Go to the start of the playback range and play the animation.
Observe how pCube1 no longer reacts to the impact of the ball, but the
ball continues to bounce off it.
In this lesson you learned some fundamental concepts with respect to
rigid body dynamics.
There are differences between active and passive rigid bodies.
When a rigid body is passive, rigid bodies will collide with it but will
not move it. You can control its movement by setting keys.
When the rigid body is active, you control its movement using dynamic
forces, specifically fields and collisions. You can change the active
and passive state of the rigid body to achieve various effects. For
example, you can roll a ball off a table using keys (passive rigid body)
then cause the ball to fall using gravity (active rigid body).
How a hinge constraint can be used between an active rigid body and a
position in the scene view
You can also create a hinge constraint between a passive rigid body and
a position in the scene view, two rigid bodies, and an active and
passive rigid body.
Other types of constraints include pin, nail, spring and barrier
constraints. For additional information on the types of constraints and
their usage, please refer to the Maya Help.
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