Hinge Joint 2D fundamentals

The Hinge Joint 2D’s is used to have a joint that allows a GameObject to rotate around a particular point, for example a door hinge, wheels, or pendulums.

You can use this joint to make two points overlap. Those two points can be two Rigidbody 2D components, or a Rigidbody 2D component and a fixed position in the world space. Connect the Hinge Joint 2D to a fixed position in the world by setting Connected Rigidbody to None. The joint applies a linear force to both connected Rigidbody 2D GameObjects.

The Hinge Joint 2D has a simulated rotational motor which you can turn on or off. Set the Maximum Motor Speed and Maximum Motor Force to control the angular speed (Torque) and make the two Rigidbody 2D GameObjects rotate in an arc relative to each other. Set the limits of the arc using Lower Angle and Upper Angle.

Constraints

Hinge Joint 2D has three simultaneous constraints. All are optional:

• Maintain a relative linear distance between two anchor points on two Rigidbody 2D GameObjects.
• Maintain an angular speed between two anchor points on two Rigidbody 2D GameObjects (limited with a maximum torque in Maximum Motor Force).
• Maintain an angle within a specified arc.

You can use this joint to construct physical GameObjects that need to behave as if they are connected with a rotational pivot. For example:

• A see-saw pivot where the horizontal section is connected to the base. Use the joint’s Angle Limits to simulate the highest and lowest point of the see-saw’s movement.
• A pair of scissors connected together with a hinge pivot. Use the joint’s Angle Limits to simulate the closing and maximum opening of the scissors.
• A simple wheel connected to the body of a car with the pivot connecting the wheel at its center to the car. In this example you can use the Hinge Joint 2D’s motor to rotate the wheel.

Additional resources

• Joints 2D
• Hinge Joint 2D component reference