Comprehensive Guide to Babylon.js Game Engine, undefined

Constraints and Joints

Connect physics objects with various types of joints:

// Create a hinge joint (like a door hinge)
const hingePivot = new BABYLON.Vector3(0, 5, 0);
const hingeAxis = new BABYLON.Vector3(0, 1, 0); // Rotate around Y axis
const hingeJoint = new BABYLON.PhysicsJoint(
    BABYLON.PhysicsJoint.HingeJoint, {
        mainPivot: hingePivot,
        connectedPivot: new BABYLON.Vector3(0, 0, 0),
        mainAxis: hingeAxis,
        connectedAxis: hingeAxis
    }
);

// Connect a box to a fixed anchor point
const anchor = BABYLON.MeshBuilder.CreateBox("anchor", {size: 0.5}, scene);
anchor.position = hingePivot;
anchor.physicsImpostor = new BABYLON.PhysicsImpostor(
    anchor,
    BABYLON.PhysicsImpostor.BoxImpostor,
    { mass: 0 }, // Fixed point (zero mass)
    scene
);

// Create a panel to act as a door
const door = BABYLON.MeshBuilder.CreateBox("door", {
    width: 0.5,
    height: 6,
    depth: 4
}, scene);
door.position = new BABYLON.Vector3(2, 5, 0);
door.physicsImpostor = new BABYLON.PhysicsImpostor(
    door,
    BABYLON.PhysicsImpostor.BoxImpostor,
    { mass: 5, friction: 0.5 },
    scene
);

// Connect the door to the anchor with a hinge joint
anchor.physicsImpostor.addJoint(door.physicsImpostor, hingeJoint);

Additional Joint Types

Other types of physical joints and constraints:

// Ball-and-socket joint (allows rotation in all directions)
const ballJoint = new BABYLON.PhysicsJoint(
    BABYLON.PhysicsJoint.BallAndSocketJoint, {
        mainPivot: new BABYLON.Vector3(0, 0, 0),
        connectedPivot: new BABYLON.Vector3(0, 2, 0)
    }
);

// Distance joint (maintains fixed distance between objects)
const distanceJoint = new BABYLON.PhysicsJoint(
    BABYLON.PhysicsJoint.DistanceJoint, {
        maxDistance: 5 // Maximum distance constraint
    }
);

// Prismatic joint (allows movement along one axis only)
const prismaticJoint = new BABYLON.PhysicsJoint(
    BABYLON.PhysicsJoint.PrismaticJoint, {
        mainAxis: new BABYLON.Vector3(1, 0, 0), // Movement along X axis
        connectedAxis: new BABYLON.Vector3(1, 0, 0)
    }
);

// Slider joint with limits
const sliderJoint = new BABYLON.PhysicsJoint(
    BABYLON.PhysicsJoint.SliderJoint, {
        mainAxis: new BABYLON.Vector3(0, 1, 0),
        connectedAxis: new BABYLON.Vector3(0, 1, 0)
    }
);
sliderJoint.setLimit(1, 5); // Min and max distance

Spring Systems

Create spring-like behavior with physics:

// Create a spring joint
const spring = new BABYLON.PhysicsJoint(
    BABYLON.PhysicsJoint.SpringJoint, {
        length: 5,          // Rest length
        stiffness: 50,      // Spring strength
        damping: 0.5,       // Damping factor
        collision: true     // Allow connected bodies to collide
    }
);

// Create anchor point
const springAnchor = BABYLON.MeshBuilder.CreateSphere("anchor", {diameter: 1}, scene);
springAnchor.position.y = 15;
springAnchor.physicsImpostor = new BABYLON.PhysicsImpostor(
    springAnchor,
    BABYLON.PhysicsImpostor.SphereImpostor,
    { mass: 0 }, // Fixed position
    scene
);

// Create suspended object
const bob = BABYLON.MeshBuilder.CreateSphere("bob", {diameter: 2}, scene);
bob.position.y = 10;
bob.physicsImpostor = new BABYLON.PhysicsImpostor(
    bob,
    BABYLON.PhysicsImpostor.SphereImpostor,
    { mass: 2, restitution: 0.6 },
    scene
);

// Connect with spring joint
springAnchor.physicsImpostor.addJoint(bob.physicsImpostor, spring);

// Visualize the spring connection with a line
const springLine = BABYLON.MeshBuilder.CreateLines("springLine", {
    points: [springAnchor.position, bob.position],
    updatable: true
}, scene);

// Update the line in the render loop
scene.onBeforeRenderObservable.add(() => {
    springLine = BABYLON.MeshBuilder.CreateLines("springLine", {
        points: [springAnchor.position, bob.position],
        instance: springLine
    });
});