Bezel Jolt

Bezel Jolt is Atlas's default physics backend. Atlas gives scripts and scenes a stable Rigidbody, query, joint, and vehicle API while Bezel translates those operations to Jolt Physics.

Add a rigidbody

The editor can attach a Rigidbody component and configure its collider, mass, friction, damping, restitution, tags, sensor state, and motion type. You can also work with the component from a script:

import { Component } from "atlas";
import { Rigidbody } from "bezel";
import { Position3d } from "atlas/units";

export class Crate extends Component {
    body: Rigidbody | null = null;

    init(): void {
        this.body = this.getParent(Rigidbody);
        this.body?.setMass(2);
        this.body?.setFriction(0.7);
        this.body?.setDamping(0.05, 0.1);
    }

    update(_deltaTime: number): void {}

    jump(): void {
        this.body?.applyImpulse(new Position3d(0, 8, 0));
    }
}

Use applyForce() for acceleration over time and applyImpulse() for an immediate change in velocity. applyForceAtPoint() can also produce torque. Direct velocity setters are useful for character or arcade-style control.

React to collisions

Collision callbacks belong on components attached to the participating objects.

import { Component, GameObject } from "atlas";
import { Debug } from "atlas/log";

export class CollisionReporter extends Component {
    init(): void {}
    update(_deltaTime: number): void {}

    onCollisionEnter(other: GameObject): void {
        Debug.print(`Started touching ${other.name}`);
    }

    onCollisionExit(other: GameObject): void {
        Debug.print(`Stopped touching ${other.name}`);
    }
}

Use a Sensor when you need contact detection without a normal solid response. Sensors can send a named signal to other components.

Query the world

Rigidbody supports raycasts, overlap tests, and movement prediction sweeps. Single-result variants expose the closest hit, while All variants collect every hit.

import { Position3d } from "atlas/units";

const result = this.body?.raycast(new Position3d(0, -1, 0), 2);
if (result?.hit?.didHit) {
    const distance = result.hit.distance;
}

Tagged raycasts limit results to bodies with selected tags. World variants accept an explicit origin, which is useful when the query should not begin at the owning rigidbody.

Joints and vehicles

Use FixedJoint to lock two members together, HingeJoint for rotation around an axis, and SpringJoint for a configurable distance constraint. A joint can connect two game objects or connect an object to the world. Configure both endpoints and anchors before initialization.

Vehicle is a component with wheel, suspension, engine, transmission, differential, steering, brake, and hand-brake settings. After changing its structural settings, call requestRecreate() so Bezel rebuilds the backend vehicle safely.

Frame timing

Atlas pushes authored transforms into physics before the simulation step and pulls simulated transforms back afterward. Apply physics inputs through components and avoid overwriting a dynamic object's transform every update(), because that fights the solver. Use a kinematic body when script-controlled movement is the intended behavior.