Rigid Body Joint Constraint¶
The Rigid Body Joint constraint is very special, it is used by the physics part of the Blender Game Engine 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.
This constraint only works with the Game Engine.
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…
This constraint is of no use in most “standard” static or animated projects. However, you can use its results outside of the BGE, through the Rigid Bodies for more info on this topic).. (see
For a demo file that shows some of the different types, see: BGE-Physics-RigidBodyJoints.blend.
In order for this constraint to work properly, both objects (so the owner and the target object) need to have Collision Bounds enabled.
- Data ID used to select the constraints target, and is not functional (red state) when it has none.
- Joint Type
- Works like an ideal ball-and-socket joint, i.e. allows rotations around all axes like a shoulder joint.
Works in one plane, like an elbow: the owner and target can only rotate around the X axis of the pivot (joint point).
- 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.
- 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:
- 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 (in the physical engine of the BGE).
- 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!
- These three numeric fields allow you to relocate the pivot point, in the owner’s space.
- These three numeric fields allow you to rotate the pivot point, in the owner’s space.