Soft/Rigid Bodies > Create Active Rigid Body

Creates an active rigid body.

Soft/Rigid Bodies > Create Active Rigid Body >

Sets the options when creating an active rigid body. The options are:

Rigid Body Name: Lets you name the rigid body for easy identification.
Active: Makes the rigid body an active rigid body. If off, the rigid body is passive.
Particle Collision: If you’ve made particles collide with the surface and the surface is an active rigid body, you can turn Particle Collision on or off to set whether the rigid body reacts to the collision force.
Allow Disconnection: By default, you cannot break connections from the rigid body to the rigid body solver that handles its dynamic animation. You can turn on Allow Disconnection so that you can break the connections. See Warning when you delete rigid body connections. Available in Attribute Editor only.
Mass: Sets the mass of an active rigid body. The greater the mass, the greater the influence on objects it collides with. Maya ignores the mass attribute of passive rigid bodies.

NoteThe Rigid options window includes checkboxes for Set Center of Mass, Set Initial Position, and Set Initial Velocity. These checkboxes make the X, Y, and Z settings for Center of Mass, Initial Position, and Initial Velocity available (or unavailable) for editing. The Set Center of Mass applies only to active rigid bodies.
Center of Mass X, Y, Z: Specifies the position of an active rigid body’s center of mass in local space coordinates. An x-shaped icon represents the center of mass. It’s easiest to see in wireframe mode.

The center of mass affects how an active rigid body bounces. For example, suppose you place a sphere’s center of mass below and to the side of the sphere’s surface. If you make the sphere fall with gravity and collide with a passive rigid body NURBS plane, the sphere bounces and bobbles around the center of mass.

The center of mass also sets the point about which an active rigid body rotates when you set the Initial Spin (described later). For example, if you set the center of mass within an active rigid body sphere, the rigid body spins about itself. If you set it outside the sphere, the sphere rotates about the center of mass.

By default, a polygonal object’s center of mass is the centroid of its bounding box. A NURBS object’s default center of mass might be slightly away from the centroid.

Maya doesn’t use the center of mass in dynamic calculations of passive rigid bodies.
Lock Center of Mass: By default, Maya recalculates a rigid body’s center of mass when you alter the object’s surface during modeling. If you turn on this attribute, Maya doesn’t change the center of mass. Available in Attribute Editor only.
Static Friction: Sets how much a rigid body resists moving from resting contact with another rigid body. For instance, if you place a ball on a sloped plane, Static Friction sets how easily the ball begins its initial slide or roll down the plane. Static friction has little or no effect after an object is moving.

A value of 0 lets the rigid body move freely. A value of 1 diminishes movement.
Dynamic Friction: Sets how much a moving rigid body resists movement against another rigid body’s surface.

A value of 0 lets the rigid body move freely. A value of 1 diminishes movement.

TipWhen two rigid bodies are in contact, the Static and Dynamic Friction of each contributes to the motion. To tune sliding and rolling of rigid bodies in contact, try various values for Static and Dynamic Friction. For example, to simulate a hockey puck sliding across wet ice, you must set Dynamic Friction to nearly 0 on the puck and ice.
Bounciness: Sets the resilience of the rigid body.
Damping: Sets an opposing force against the rigid body’s movement. This attribute is similar to drag; it affects object movement before, during, and after contact with another object. A positive value diminishes movement. A negative value increases movement.
Impulse X, Y, Z: Creates an instantaneous force, with magnitude and direction, on the rigid body at the local space position specified in Impulse Position X, Y, Z. The higher the number, the greater the magnitude of force. For more details, see Keying impulses to rigid bodies.
Impulse Position X, Y, Z: Specifies the position in the rigid body’s local space where the impulse strikes. If the impulse strikes a point other than the center of mass, the rigid body rotates about its center of mass in addition to moving with the change to its velocity.

If you specify a position outside the object’s surface boundaries, you’ll still see rotation and velocity. Note that the 0, 0, 0 position of an object’s local space is at the center of its bounding box.
Spin Impulse X, Y, Z: Applies an instantaneous rotational force (torque) on the rigid body’s center of mass in the direction you specify by the X, Y, and Z values. These values set magnitude and direction. The higher the number, the greater the magnitude of the rotational force.

NoteThe Attribute Editor displays the current Velocity, Spin, Force, and Torque of a rigid body. See Get data on velocity, forces, and collisions for details on these read-only attributes.
Solver Id: The read-only rigid body index number the solver uses to calculate dynamics for this rigid body. You can use the Solver Id in MEL scripts and expressions to identify a specific rigid body in the solver.

Initial Settings attributes

Initial Spin X, Y, Z: Sets the initial angular velocity of the rigid body. This spins the rigid body.
Initial Position X, Y, Z: Sets the initial position of the rigid body in world space.
Initial Orientation X, Y, Z: Sets the initial local space orientation of the rigid body. For example, an Initial Orientation X value of 90 means the object has an orientation of 90 degrees rotation about its X-axis. This assumes you are using the degrees rather than radians as your working units.
Initial Velocity X, Y, Z: Sets the initial speed and direction of the rigid body.

Performance Attributes

Stand In: Displays a menu that lets you select a simple internal cube or sphere as a stand-in for rigid body calculations. The original object remains visible in the scene. If you use a stand-in sphere or cube, playback speed improves but collision reactions differ from the actual object. To use the actual geometry, select none.
Apply Force At: Displays a menu that lets you set whether forces affect a rigid body at its center of mass, the corners of its bounding box, or its CVs or vertices
Center of Mass: Applies force to a single position at the center of mass. No torque is imparted to the rigid body.
Bounding Box: Applies force to the eight corners of the object’s bounding box. This is the default setting. To see the object’s bounding box, select Shading > Bounding Box from the menus above the workspace pane.
Vertices or CVs: Applies force at each vertex of polygonal objects, or at each CV of NURBS surfaces. This is the slowest but most accurate choice.
Tessellation Factor: Maya internally converts NURBS objects to polygons before it animates rigid body dynamics. The Tessellation Factor sets the approximate number of polygons created during the conversion. Lower numbers create coarser geometry and lessen animation accuracy, but increase the playback speed.

Increase the Tessellation Factor if you are bouncing an object on a bumpy, irregular surface. Experiment with various values until you see the desired result.

If you change the Tessellation Factor, the internal conversion occurs once, immediately after you change its value. This takes some time for complex NURBS surfaces. Increasing the Tessellation Factor increases the time for Maya to detect rigid body collisions.
Collision Layer: You can use collision layers to create exclusive groups of objects that collide with each other. Only rigid bodies with the same collision layer number can collide with each other.

For example, suppose you have four objects moving towards each other, but you want one of the objects to pass through without colliding. You can assign the non-colliding object a different collision layer number.

By putting rigid bodies that don’t collide in different collision layers, you can lessen collision processing time.

A rigid body in collision layer -1 (minus 1) will collide with all rigid bodies in the solver, regardless of their collision layer numbers.
Collisions: When off, the rigid body doesn’t collide with any objects in a scene.

TipYou can turn on the Interpenetrate attribute of two or more rigid bodies to prevent only those objects from colliding with each other. To do this, select the objects then select Solvers > Set Rigid Body Interpenetration. To turn off the Interpenetrate attribute later, select the objects then select Solver > Set Rigid Body Collision.
Ignore: When on, this turns off the influence of fields, collisions, and any other rigid body effects. This is useful if you have a scene with many computation-intensive rigid bodies and want to disable several to speed up animation play.