threejs/examples/jsm/physics/OimoPhysics.js

import * as OIMO from '../libs/OimoPhysics/index.js';

async function OimoPhysics() {

	const frameRate = 60;

	const world = new OIMO.World( 2, new OIMO.Vec3( 0, - 9.8, 0 ) );

	//

	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;

			return new OIMO.OBoxGeometry( new OIMO.Vec3( sx, sy, sz ) );

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

			const radius = parameters.radius !== undefined ? parameters.radius : 1;

			return new OIMO.OSphereGeometry( radius );

		}

		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 shapeConfig = new OIMO.ShapeConfig();
		shapeConfig.geometry = shape;

		const bodyConfig = new OIMO.RigidBodyConfig();
		bodyConfig.type = mass === 0 ? OIMO.RigidBodyType.STATIC : OIMO.RigidBodyType.DYNAMIC;
		bodyConfig.position = new OIMO.Vec3( mesh.position.x, mesh.position.y, mesh.position.z );

		const body = new OIMO.RigidBody( bodyConfig );
		body.addShape( new OIMO.Shape( shapeConfig ) );
		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 shapeConfig = new OIMO.ShapeConfig();
			shapeConfig.geometry = shape;

			const bodyConfig = new OIMO.RigidBodyConfig();
			bodyConfig.type = mass === 0 ? OIMO.RigidBodyType.STATIC : OIMO.RigidBodyType.DYNAMIC;
			bodyConfig.position = new OIMO.Vec3( array[ index + 12 ], array[ index + 13 ], array[ index + 14 ] );

			const body = new OIMO.RigidBody( bodyConfig );
			body.addShape( new OIMO.Shape( shapeConfig ) );
			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.setPosition( new OIMO.Vec3( position.x, position.y, position.z ) );

		} else if ( mesh.isMesh ) {

			const body = meshMap.get( mesh );

			body.setPosition( new OIMO.Vec3( position.x, position.y, position.z ) );

		}

	}

	//

	let lastTime = 0;

	function step() {

		const time = performance.now();

		if ( lastTime > 0 ) {

			// console.time( 'world.step' );
			world.step( 1 / frameRate );
			// 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 ];

					compose( body.getPosition(), body.getOrientation(), array, j * 16 );

				}

				mesh.instanceMatrix.needsUpdate = true;

			} else if ( mesh.isMesh ) {

				const body = meshMap.get( mesh );

				mesh.position.copy( body.getPosition() );
				mesh.quaternion.copy( body.getOrientation() );

			}

		}

	}

	// 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;

}

export { OimoPhysics };