threejs/examples/js/physics/AmmoPhysics.js

( function () {

	async function AmmoPhysics() {

		if ( 'Ammo' in window === false ) {

			console.error( 'AmmoPhysics: Couldn\'t find Ammo.js' );
			return;

		}

		const AmmoLib = await Ammo(); // eslint-disable-line no-undef

		const frameRate = 60;
		const collisionConfiguration = new AmmoLib.btDefaultCollisionConfiguration();
		const dispatcher = new AmmoLib.btCollisionDispatcher( collisionConfiguration );
		const broadphase = new AmmoLib.btDbvtBroadphase();
		const solver = new AmmoLib.btSequentialImpulseConstraintSolver();
		const world = new AmmoLib.btDiscreteDynamicsWorld( dispatcher, broadphase, solver, collisionConfiguration );
		world.setGravity( new AmmoLib.btVector3( 0, - 9.8, 0 ) );
		const worldTransform = new AmmoLib.btTransform();

		//

		function getShape( geometry ) {

			const parameters = geometry.parameters;

			// TODO change type to is*

			if ( geometry.type === 'BoxGeometry' ) {

				const sx = parameters.width !== undefined ? parameters.width / 2 : 0.5;
				const sy = parameters.height !== undefined ? parameters.height / 2 : 0.5;
				const sz = parameters.depth !== undefined ? parameters.depth / 2 : 0.5;
				const shape = new AmmoLib.btBoxShape( new AmmoLib.btVector3( sx, sy, sz ) );
				shape.setMargin( 0.05 );
				return shape;

			} else if ( geometry.type === 'SphereGeometry' || geometry.type === 'IcosahedronGeometry' ) {

				const radius = parameters.radius !== undefined ? parameters.radius : 1;
				const shape = new AmmoLib.btSphereShape( radius );
				shape.setMargin( 0.05 );
				return shape;

			}

			return null;

		}

		const meshes = [];
		const meshMap = new WeakMap();
		function addMesh( mesh, mass = 0 ) {

			const shape = getShape( mesh.geometry );
			if ( shape !== null ) {

				if ( mesh.isInstancedMesh ) {

					handleInstancedMesh( mesh, mass, shape );

				} else if ( mesh.isMesh ) {

					handleMesh( mesh, mass, shape );

				}

			}

		}

		function handleMesh( mesh, mass, shape ) {

			const position = mesh.position;
			const quaternion = mesh.quaternion;
			const transform = new AmmoLib.btTransform();
			transform.setIdentity();
			transform.setOrigin( new AmmoLib.btVector3( position.x, position.y, position.z ) );
			transform.setRotation( new AmmoLib.btQuaternion( quaternion.x, quaternion.y, quaternion.z, quaternion.w ) );
			const motionState = new AmmoLib.btDefaultMotionState( transform );
			const localInertia = new AmmoLib.btVector3( 0, 0, 0 );
			shape.calculateLocalInertia( mass, localInertia );
			const rbInfo = new AmmoLib.btRigidBodyConstructionInfo( mass, motionState, shape, localInertia );
			const body = new AmmoLib.btRigidBody( rbInfo );
			// body.setFriction( 4 );
			world.addRigidBody( body );
			if ( mass > 0 ) {

				meshes.push( mesh );
				meshMap.set( mesh, body );

			}

		}

		function handleInstancedMesh( mesh, mass, shape ) {

			const array = mesh.instanceMatrix.array;
			const bodies = [];
			for ( let i = 0; i < mesh.count; i ++ ) {

				const index = i * 16;
				const transform = new AmmoLib.btTransform();
				transform.setFromOpenGLMatrix( array.slice( index, index + 16 ) );
				const motionState = new AmmoLib.btDefaultMotionState( transform );
				const localInertia = new AmmoLib.btVector3( 0, 0, 0 );
				shape.calculateLocalInertia( mass, localInertia );
				const rbInfo = new AmmoLib.btRigidBodyConstructionInfo( mass, motionState, shape, localInertia );
				const body = new AmmoLib.btRigidBody( rbInfo );
				world.addRigidBody( body );
				bodies.push( body );

			}

			if ( mass > 0 ) {

				meshes.push( mesh );
				meshMap.set( mesh, bodies );

			}

		}

		//

		function setMeshPosition( mesh, position, index = 0 ) {

			if ( mesh.isInstancedMesh ) {

				const bodies = meshMap.get( mesh );
				const body = bodies[ index ];
				body.setAngularVelocity( new AmmoLib.btVector3( 0, 0, 0 ) );
				body.setLinearVelocity( new AmmoLib.btVector3( 0, 0, 0 ) );
				worldTransform.setIdentity();
				worldTransform.setOrigin( new AmmoLib.btVector3( position.x, position.y, position.z ) );
				body.setWorldTransform( worldTransform );

			} else if ( mesh.isMesh ) {

				const body = meshMap.get( mesh );
				body.setAngularVelocity( new AmmoLib.btVector3( 0, 0, 0 ) );
				body.setLinearVelocity( new AmmoLib.btVector3( 0, 0, 0 ) );
				worldTransform.setIdentity();
				worldTransform.setOrigin( new AmmoLib.btVector3( position.x, position.y, position.z ) );
				body.setWorldTransform( worldTransform );

			}

		}

		//

		let lastTime = 0;
		function step() {

			const time = performance.now();
			if ( lastTime > 0 ) {

				const delta = ( time - lastTime ) / 1000;

				// console.time( 'world.step' );
				world.stepSimulation( delta, 10 );
				// console.timeEnd( 'world.step' );

			}

			lastTime = time;

			//

			for ( let i = 0, l = meshes.length; i < l; i ++ ) {

				const mesh = meshes[ i ];
				if ( mesh.isInstancedMesh ) {

					const array = mesh.instanceMatrix.array;
					const bodies = meshMap.get( mesh );
					for ( let j = 0; j < bodies.length; j ++ ) {

						const body = bodies[ j ];
						const motionState = body.getMotionState();
						motionState.getWorldTransform( worldTransform );
						const position = worldTransform.getOrigin();
						const quaternion = worldTransform.getRotation();
						compose( position, quaternion, array, j * 16 );

					}

					mesh.instanceMatrix.needsUpdate = true;

				} else if ( mesh.isMesh ) {

					const body = meshMap.get( mesh );
					const motionState = body.getMotionState();
					motionState.getWorldTransform( worldTransform );
					const position = worldTransform.getOrigin();
					const quaternion = worldTransform.getRotation();
					mesh.position.set( position.x(), position.y(), position.z() );
					mesh.quaternion.set( quaternion.x(), quaternion.y(), quaternion.z(), quaternion.w() );

				}

			}

		}

		// animate

		setInterval( step, 1000 / frameRate );
		return {
			addMesh: addMesh,
			setMeshPosition: setMeshPosition
			// addCompoundMesh
		};

	}

	function compose( position, quaternion, array, index ) {

		const x = quaternion.x(),
			y = quaternion.y(),
			z = quaternion.z(),
			w = quaternion.w();
		const x2 = x + x,
			y2 = y + y,
			z2 = z + z;
		const xx = x * x2,
			xy = x * y2,
			xz = x * z2;
		const yy = y * y2,
			yz = y * z2,
			zz = z * z2;
		const wx = w * x2,
			wy = w * y2,
			wz = w * z2;
		array[ index + 0 ] = 1 - ( yy + zz );
		array[ index + 1 ] = xy + wz;
		array[ index + 2 ] = xz - wy;
		array[ index + 3 ] = 0;
		array[ index + 4 ] = xy - wz;
		array[ index + 5 ] = 1 - ( xx + zz );
		array[ index + 6 ] = yz + wx;
		array[ index + 7 ] = 0;
		array[ index + 8 ] = xz + wy;
		array[ index + 9 ] = yz - wx;
		array[ index + 10 ] = 1 - ( xx + yy );
		array[ index + 11 ] = 0;
		array[ index + 12 ] = position.x();
		array[ index + 13 ] = position.y();
		array[ index + 14 ] = position.z();
		array[ index + 15 ] = 1;

	}

	THREE.AmmoPhysics = AmmoPhysics;

} )();