Constraints

In the physics engine, Constraints are used to simulate connections between objects, such as rods, strings, springs, or ragdolls.

Constraints depend on Rigidbody. If the node does not have a rigidbody component, the engine will automatically add a rigidbody component when adding constraints.

Note: The current constraint only works if the physics engine is selected as Bullet, PhysX or Cannon.js.

HingeConstraint

Hinge constraints constrain the motion of connected objects to a certain axis. This constraint is useful in situations such as simulating the hinge of a door or the rotation of a motor.

Properties	Description
AttachedBody	Rigid body components under the node where the current constraint is located
ConnectedBody	Gets or sets the rigid body to which the constraint is connected, null means it is linked to a static body at the world origin
EnableCollision	Gets or sets whether collision is enabled between two bodies connected by a constraint
PivotA	Constrain the relative position of a joint in the local space of its own rigid body
PivotB	Constrain the relative position of the joint in the local space of the connected rigid body
Axis	The axis that constrains constraint rotation in local space

Please refer to HingeConstraint API for the hinge constraint interface.

PointToPointConstraint

A point-to-point constraint is a simple composite constraint that connects two objects, or one object, to a point in the coordinate system. The connected objects can be freely rotated with respect to each other while sharing a common connection point.

Properties	Description
AttachedBody	The rigid body to which the collider is attached
ConnectedBody	Gets or sets the body to which the constraint is connected
EnableCollision	Gets or sets whether collision is enabled between two bodies connected by a constraint
PivotA	Constrain the relative position of a joint in the local space of its own rigid body
PivotB	Constrain the relative position of the joint in the local space of the connected rigid body

For point-to-point constraint interface, please refer to PointToPointConstraint API.

FixedConstraint

A fixed constraint is the simplest constraint, it locks the relative position and rotation of two rigid bodies. The connected objects are not allowed to move relatively to each other.

Properties	Description
AttachedBody	The rigid body to which the collider is attached
ConnectedBody	Gets or sets the body to which the constraint is connected
EnableCollision	Gets or sets whether collision is enabled between two bodies connected by a constraint
BreakForce	Gets or sets the maximum force that can be applied to the constraint before it breaks
BreakTorque	Gets or sets the maximum torque that can be applied to the constraint before it breaks

For point-to-point constraint interface, please refer to FixedConstraint API.