Rigid Body Properties Editor

Determines how the rigid body behaves during the dynamic simulation and how it reacts during collisions.

To apply: Select an object and choose Create Rigid Body Active or Passive Rigid Body from the Simulate toolbar.

To redisplay: Select the rigid body and choose Modify Rigid Body Edit Rigid Body from the Simulate toolbar. You can also click the rigid body's Rigid Body Properties icon in the explorer.

Mute

Toggles the availability of the rigid body in simulation calculations.

Passive

Toggles the active/passive state of the rigid body.

If this option is selected, the rigid body is passive and is not affected by forces or moved as a result of a collision. However, passive rigid bodies can be used as stationary objects in collisions and rigid body constraints.

If this option is not selected, the rigid body is active. Active rigid bodies are affected by forces and move as a result of collisions with other rigid bodies.

For more information, see Active or Passive? [ Simulation and Effects].

Collisions

Collide with	Sets the availability of the rigid body for collisions: Everything makes the rigid body available for collisions with all rigid bodies in the current environment, regardless of their Collision Layer numbers. Nothing makes the rigid body unavailable for any collisions. Layer allows the rigid body to collide only with other rigid bodies that have matching collision Layer numbers.
Layer	If the Collide with Layer option is selected, you can enter a number for the layer in which you want the rigid body to be. By default, all rigid bodies have a collision layer value of 0 meaning that they can all collide with each other. For more information, see Setting Up Collision Layers [ Simulation and Effects].
Collision Type	Type of geometry to be used for the rigid body's collision: Bounding shapes (Box, Sphere, or Capsule) provide a quick solution for collisions when shape accuracy is not an issue or the bounding shape's geometry is close enough to the shape of the rigid body. Convex Hull is available only for the PhysX dynamics engine. Convex hulls give a quick approximation of an object's actual shape, with the results similar to a box being shrinkwrapped around object. Convex hull doesn't calculate any dips or holes in the rigid body geometry, but is otherwise the same as the rigid body's original shape. Actual Shape provides an accurate collision but takes longer to calculate than bounding shapes or convex hulls. You may need to use the actual shape for rigid body geometry that is irregular in shape or has holes, dips, or peaks that you want to consider for the collision. When you select this option with PhysX as the dynamics engine, collision data is created to calculate each rigid body's geometry for the collision. This collision data is based on the rigid body's actual shape collision volume. For more information on these collision types, see Selecting a Collision Geometry Type [ Simulation and Effects].
Detail	This is available only when the Collision Type is Actual Shape and PhysX is set as the current dynamics engine. This parameter lets you define how accurately you want the collision data to follow the rigid body's shape. You can set the resolution to Low, Medium, High, or Coffee break. For more information, see Actual Shape - PhysX [ Simulation and Effects].
Subdivision Level	This applies only when the Collision Type is Actual Shape. This parameter determines the definition of the surface used for the collision geometry. The higher this value, the smoother the surface used for collisions and the more accurate the collision. For more information, see Actual Shape - PhysX [ Simulation and Effects].
Animatable Deformation	Detects collisions based on the change in the geometry of rigid bodies that have animated deformations applied to them (such as shape animation, envelopes, or lattices). You should leave this option off unless you need it because it can use lots of memory.

Surface Properties

The values for the Friction and Elasticity parameters for each collision object are multiplied by the values of the corresponding parameters set for other collision objects. That means that the results of a collision are modulated by the elasticity and friction of all colliding rigid bodies.

To keep this relationship simple, it's usually best to set the values for only one collision object at a time and test out the results.

Elasticity

Also called the coefficient of restitution, this is the factor that influences the amount of energy that is retained to move rigid bodies in the opposite direction (bounce) during a collision.

A value of 0 means that a rigid body will not bounce in a collision because no energy is retained. A value of 1 means that the rigid body will not lose any energy and therefore bounce back with a speed equal and opposite to what it had before the collision.

Note that due to possible numerical inaccuracies, a rigid body may bounce back even if this value is 0, and it may lose kinetic energy even if this value is 1.

You can enter values higher than allowed by the slider range, but you cannot enter negative values. For example, you may want to set use a value greater than 1 for effects such as creating a jumping bean or a bouncing ball. However, using values above 1 makes the rigid body return more energy at each collision, and can make a simulation less stable.

Static Friction

The resistive force that tends to oppose a rigid body from changing its state from resting to motion when in contact with another rigid body. It has little or no effect after an object is moving. In general, static friction is greater than dynamic friction.

The value range is between 0 and 1, with 0 being no friction (free movement) and 1 being full friction (no movement). You cannot enter negative values or values over 1.

Dynamic Friction

This type of friction is available only for the PhysX dynamics engine.

This is the resistive force acting between rigid bodies that tends to dampen motion. Dynamic (also known as kinetic) friction is how much a moving rigid body resists movement against another rigid body's surface. This force is generally proportional to any force that has been applied to the rigid body, so you can think of it as the ratio of frictional force to the applied force on the body.

The value range is between 0 and 1, with 0 being no friction (free movement) and 1 being full friction (no movement). You cannot enter negative values or values over 1.

Velocity/Acceleration Limits

These parameters put a soft limit on the maximum velocity and acceleration of a rigid body. Because collisions happen very quickly, they can cause large but accurate accelerations that can make the rigid bodies become unstable when they collide. These parameters can help solve any interpenetration problems of the rigid body geometries in a collision that make them seem to "explode" off into space. Generally, you shouldn't need to set these limits, but they may help solve this type of simulation problem.

For more information, see Setting Limits on the Rigid Body's Velocity and Acceleration [ Simulation and Effects].

Velocity Limits Active	Toggles the activeness of the velocity limits.
Linear Limit	Sets the limit on the rigid body's linear velocity. Values are in Softimage units.
Angular Limit	Sets the limit on the rigid body's angular velocity. Values are in radians.
Acceleration Limits Active	Toggles the activeness of the acceleration limits.
Linear Limit	Sets the limit on the rigid body's linear acceleration. Values are in Softimage units.
Angular Limit	Sets the limit on the rigid body's angular acceleration. Values are in radians.

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