Rigid Body Joint Constraint

The Rigid Body Joint constraint is very special, it is used to simulate a joint between its owner and its target. It offers four joint types: hinge type, ball-and-socket type, cone-twist type, and generic six-DoF type.

The joint point and axes are defined and fixed relative to the owner. The target moves as if it were stuck to the center point of a stick, the other end of the stick rotating around the joint/pivot point…

For a demo file that shows some of the different types, see: BGE-Physics-RigidBodyJoints.blend.

Note

In order for this constraint to work properly, both objects (so the owner and the target object) need to have Collision Bounds enabled.

Options

../../../_images/rigging_constraints_relationship_rigid-body-joint_panel.png

Rigid Body Joint panel.

Target
Data ID used to select the constraints target, and is not functional (red state) when it has none.
Joint Type
Ball
Works like an ideal ball-and-socket joint, i.e. allows rotations around all axes like a shoulder joint.
Hinge

Works in one plane, like an elbow: the owner and target can only rotate around the X axis of the pivot (joint point).

Limits
Angular limits for the X axis.
Cone Twist

Similar to Ball, this is a point-to-point joint with limits added for the cone and twist axis.

Limits
Angular limits.
Generic 6DOF

Works like the Ball option, but the target is no longer constrained at a fixed distance from the pivot point, by default (hence the six degrees of freedom: rotation and translation around/along the three axes). In fact, there is no longer a joint by default, with this option, but it enables additional settings which allow you to restrict some of these DoF:

Limits
Linear and angular limits for a given axis (of the pivot) in Blender Units and degrees respectively.
Child Object
Normally, leave this blank. You can reset it to blank by right-clicking and selecting Reset to Default Value.
Linked Collision
When enabled, this will disable the collision detection between the owner and the target.
Display Pivot
When enabled, this will draw the pivot of the joint in the 3D Views. The most useful, especially with the Generic 6DOF joint type!
Pivot
These three numeric fields allow you to relocate the pivot point, in the owner’s space.
Axis
These three numeric fields allow you to rotate the pivot point, in the owner’s space.