RBD simulations

Overview

The RBD solver simulates rigid bodies, solid objects that don’t change shape, as they collide with other objects. RBD stands for rigid body dynamics.

RBD objects can be active and passive. Active objects are affected by forces and collisions. Passive objects can be collided with by active objects, but don’t move, and are not affected by forces.

See relationships for how to make cloth interact with other objects. See also how to switch between keyframe animation and simulation.

Shelf tools

The Rigid Bodies shelf tab contains tools for creating and constraining RBD objects. You can also use the forces on the Drive simulation shelf tab to affect the objects.

Important nodes

Important RBD Object parameters

Use deforming geometry

For efficiency, the dynamics engine does not use animated geometry by default. To have the RBD object use animated geometry, set Use animated geometry to 1 in the RBD Object’s parameters. You can animate the value of this option, so you can only use animation in the time periods where it matters, and switch back to static geometry in other places for efficiency.

Number of objects

In an RBD Object’s parameters, set the Number of objects parameter.
The RBD object node creates multiple copies of the object, but creates them at the exact same position, so they overlap and still appear to be one object. You need to use an expression in the object’s Position parameter to space them out.
In the Position parameter (on the Initial State tab), enter an expression that uses the $OBJ (“object number”) local variable to position the copies.
For example, use $OBJ * 2 in the Position X field to space the copies 2 units apart along the positive X axis. The expression is evaluated for each copy with $OBJ set to the current copy number.