Conveyor Belts

Turns the upper surface of an existing body into a moving physical contact surface.

jolt_conveyor attaches a managed native helper to one non-sensor Static or Kinematic JoltBody. Dynamic cargo is transported by Jolt's contact solver and friction: its position, rotation and velocity are never teleported, and ordinary collisions remain active.

Syntax#

jolt_conveyor(body, options=undefined)

Arguments#

Options#

Public methods#

Contact and movement rules#

• Only Dynamic, non-sensor rigid bodies in real upper-surface contact are transported. Airborne, side-contact and underside bodies are ignored.
• The top test uses the host's local +Z normal and accepts contact normals inside a 60-degree top cone.
• Speed is a target relative surface velocity, not an impulse accumulated every Step. Friction, normal force, cargo mass and contact conditions determine the actual response.
• Boxes translate while spheres and cylinders can roll naturally. Cargo-to-cargo collision and all normal contact response remain active.
• LOCAL direction follows rotated or inclined hosts. WORLD stays absolute, but is still projected onto the upper tangent plane and cannot create lift.
• Changing speed, direction, layers or smart assistance wakes eligible bodies touching the real host shape.

Centering and rotation alignment#

• Centering applies a capped lateral PD force toward the line through the public host origin in the conveyor direction. It has no forward component and never teleports cargo.
• Rotation alignment applies capped torque around the surface normal toward the nearest rotation_step multiple relative to the host orientation.
• Alignment controls projected yaw only; it is not full three-dimensional upright stabilization.
• Both smart helpers operate only during top contact and can be resisted by mass, friction and other colliders.

Example#

var conveyor_body = jolt_box_create_static(0, 0, 0, 3, 20, 0.5, {
    friction: 0.8
});

var belt = jolt_conveyor(conveyor_body, {
    direction: {x:0, y:1, z:0},
    speed: 2,
    center_objects: true,
    center_strength: 100,
    align_rotation: true,
    rotation_step: 90,
    rotation_strength: 50
});

Runtime control#

belt.set_speed(-2); // Reverse
belt.set_speed(0);  // Stop physical surface motion

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.