Hinge Constraint

Keeps a shared anchor together and permits relative rotation around one world-space axis.

Use a Hinge for doors, levers, wheels and powered pivots. It provides angular limits in degrees, a changeable reference rotation, current-angle state, and torque-limited velocity or position motors.

Syntax#

jolt_hinge(body_a, body_b, anchor_x, anchor_y, anchor_z, axis_x, axis_y, axis_z, options=undefined)
jolt_hinge_world(body, anchor_x, anchor_y, anchor_z, axis_x, axis_y, axis_z, options=undefined)

Arguments#

Options#

Methods#

Example: limited door#

var frame = jolt_box_create_static(-1.8, 0, 2, 0.3, 0.3, 4);
var door  = jolt_box_create_dynamic(0, 0, 2, 3.6, 0.25, 4, { mass: 18 });

var hinge = jolt_hinge(frame, door, -1.8, 0, 2, 0, 0, 1, {
    limits_min: 0,
    limits_max: 110,
    collision: false
});

Example: position and velocity motors#

hinge.set_motor_max_torque(45);
hinge.set_motor_spring(3, 0.8);
hinge.set_motor_position(90); // degrees

// Later, switch to continuous velocity mode.
hinge.set_motor_velocity(4);  // radians per second

var angle = hinge.get_angle();
var state = hinge.get_motor_state();

Reference rotation#

set_rotation(angle) redefines the Hinge zero angle while preserving its handle, anchor, limits, collision state and motor settings. Existing limits are then measured from the new reference.

World variant#

var lever = jolt_box_create_dynamic(0, 0, 2, 4, 0.3, 0.3, { mass: 6 });
var pivot = jolt_hinge_world(lever, -2, 0, 2, 0, 1, 0, {
    limits_min: -35,
    limits_max: 35
});

Errors and lifecycle#

• Body-to-body creators require two different live managed JoltBody values in the same managed default world.
• At least one connected body must be movable; native Jolt rejects an unsupported static-static pair.
• Constructors return a managed JoltConstraint on success or undefined after a validation/native creation failure.
• Destroying either attached body automatically destroys and invalidates the constraint before releasing that body.
• Read jolt_get_error() after a failed creator or method when the values may be untrusted.
• Anchor and axis components must be finite and the axis must have non-zero length.
• Limits must be finite and ordered; motor torque must be finite and non-negative.
• If both motor_velocity and motor_position are supplied, position is applied last and becomes the active mode.

Verified operation contracts#

These contracts distinguish units, return values, errors and lifetime according to the current implementation. Check results: false, 0 and undefined can mean different things for different methods.