Guides

Physics guide

Build a stable Jolt simulation with reusable shapes, fixed stepping, and explicit rendering sync.

Create one game-owned world, reuse colliders, create bodies with an explicit motion type, optimize the broadphase after initial setup, and step it from the game loop:

typescript

import { BoxCollider, Game, MotionType, PhysicsWorld } from '@bornengine/engine';

const game = new Game();
const world = new PhysicsWorld(game, { gravity: { x: 0, y: -9.81, z: 0 } });
const groundShape = new BoxCollider(world, { x: 50, y: 0.5, z: 50 });
const ground = world.createBody(groundShape, {
  motionType: MotionType.STATIC,
  position: { x: 0, y: -0.5, z: 0 },
});

world.optimizeBroadphase();
game.run({
  update(deltaTime) { world.step(deltaTime); },
  render() {},
  onStop: () => game.dispose(),
});

PhysicsWorld.step() uses a fixed internal timestep with an accumulator and returns interpolation alpha. Use world.setInterpolation(true) for smoothed body transforms or read world.stepAlpha to blend your own values. stepVariable() exists when your game owns the accumulator.

Larger systems

Characters use world.createCharacter() and their controller instance, soft bodies use world.createSoftBody() with vertex positions and inverse masses, and vehicles expose chassis and wheel transforms through world.createVehicle(). Native and Web/WASM share the class surface; check target-specific limitations before relying on a feature.

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