Hinge Joint

Hinge joints are used to simulate the connection of two objects through an axis, allowing them to rotate freely around this axis. This type of joint is commonly used to implement door hinges, wheels, pendulums, and other physical effects that require rotation around a fixed axis.

Usage

1. Select the target entity and click the add component button in the inspector to add the HingeJoint component.

2. Use the connectedCollider property of the component to set the target collider to connect to (if not needed, keep it as null, which means connecting to a point in world space).

3. Adjust the joint's properties as needed to modify its behavior. Refer to the descriptions below for the meaning and function of each property.

Property Descriptions

Collider Settings

• connectedCollider
  Specifies the target collider to connect to. When set to null, the joint connects to a fixed point in world space.

Anchor Settings

• anchor
  Defines the anchor point on the main collider (local coordinates). This point is the rotation center of the hinge.

• connectedAnchor
  Defines the connection point position:

  • When connectedCollider is null, it represents a fixed point in world space
  • When connectedCollider is not null, it represents the connection point in the local space of the target collider

• automaticConnectedAnchor
  Whether to automatically calculate the connection point position. When enabled, it automatically maintains the initial relative position of the objects.

Rotation Settings

• axis
  Defines the direction of the hinge's rotation axis. Objects will rotate along this axis.

Motion Limits

• useLimits
  Whether to enable angle limits. When enabled, the rotation range of the hinge can be limited.

• limits
  Sets the rotation range of the hinge:

Motor Drive

• useMotor
  Whether to enable the motor function. When enabled, the hinge can be actively driven to rotate.

• motor
  Motor parameter settings:

Spring Settings

• useSpring
  Whether to enable the spring effect. When enabled, the limiter will exhibit elastic characteristics.

Break Thresholds

• breakForce
  The maximum force the joint can withstand before breaking.

• breakTorque
  The maximum torque the joint can withstand before breaking.

Mass Calculation Intervention

• connectedMassScale and massScale
  Adjust the mass influence of the connected collider and the main collider. The default value is 1.0.

Script Usage

Basic Usage

// Add Hinge Joint component
const hingeJoint = entity.addComponent(HingeJoint);
 
// Set the connected object
hingeJoint.connectedCollider = targetEntity.getComponent(Collider);
 
// Set the rotation axis
hingeJoint.axis.setValue(0, 1, 0); // Rotate around Y-axis

Motion Limits

// Enable angle limits
hingeJoint.useLimits = true;
hingeJoint.limits = new JointLimits();
hingeJoint.limits.min = -45;         // Minimum angle
hingeJoint.limits.max = 45;          // Maximum angle
hingeJoint.limits.contactDistance = 5; // Contact distance
 
// Enable elastic limits
hingeJoint.useSpring = true;
hingeJoint.limits.stiffness = 100;  // Spring stiffness
hingeJoint.limits.damping = 0.2;    // Damping coefficient

Motor Drive

// Enable motor
hingeJoint.useMotor = true;
hingeJoint.motor = new JointMotor();
hingeJoint.motor.targetVelocity = 180;  // Target angular velocity (degrees/second)
hingeJoint.motor.forceLimit = 500;      // Maximum torque
hingeJoint.motor.freeSpin = false;      // Free spin
hingeJoint.motor.gearRatio = 1;         // Gear ratio

Get Motion Information

// Get current angle
const currentAngle = hingeJoint.angle;
 
// Get current angular velocity
const angularVelocity = hingeJoint.velocity;