examples/physics_ammo_rope.html

<html lang="en">
	<head>
		<title>Amjs softbody rope demo</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
		<link type="text/css" rel="stylesheet" href="main.css">
		<style>
			body {
				color: #333;
			}
		</style>
	</head>
	<body>
	<div id="info">Ammo.js physics soft body rope demo<br>Press Q or A to move the arm.</div>
	<div id="container"></div>

	<script src="jsm/libs/ammo.wasm.js"></script>

	<script type="importmap">
		{
			"imports": {
				"three": "../build/three.module.js",
				"three/addons/": "./jsm/"
			}
		}
	</script>

	<script type="module">
		import * as THREE from 'three';

		import Stats from 'three/addons/libs/stats.module.js';

		import { OrbitControls } from 'three/addons/controls/OrbitControls.js';

		// Graphics variables
		let container, stats;
		let camera, controls, scene, renderer;
		let textureLoader;
		const clock = new THREE.Clock();

		// Physics variables
		const gravityConstant = - 9.8;
		let collisionConfiguration;
		let dispatcher;
		let broadphase;
		let solver;
		let softBodySolver;
		let physicsWorld;
		const rigidBodies = [];
		const margin = 0.05;
		let hinge;
		let rope;
		let transformAux1;

		let armMovement = 0;

		Ammo().then( function ( AmmoLib ) {

			Ammo = AmmoLib;

			init();

		} );

		function init() {

			initGraphics();

			initPhysics();

			createObjects();

			initInput();

		}

		function initGraphics() {

			container = document.getElementById( 'container' );

			camera = new THREE.PerspectiveCamera( 60, window.innerWidth / window.innerHeight, 0.2, 2000 );

			scene = new THREE.Scene();
			scene.background = new THREE.Color( 0xbfd1e5 );

			camera.position.set( - 7, 5, 8 );

			renderer = new THREE.WebGLRenderer( { antialias: true } );
			renderer.setPixelRatio( window.devicePixelRatio );
			renderer.setSize( window.innerWidth, window.innerHeight );
			renderer.setAnimationLoop( animate );
			renderer.shadowMap.enabled = true;
			container.appendChild( renderer.domElement );

			controls = new OrbitControls( camera, renderer.domElement );
			controls.target.set( 0, 2, 0 );
			controls.update();

			textureLoader = new THREE.TextureLoader();

			const ambientLight = new THREE.AmbientLight( 0xbbbbbb );
			scene.add( ambientLight );

			const light = new THREE.DirectionalLight( 0xffffff, 3 );
			light.position.set( - 10, 10, 5 );
			light.castShadow = true;
			const d = 10;
			light.shadow.camera.left = - d;
			light.shadow.camera.right = d;
			light.shadow.camera.top = d;
			light.shadow.camera.bottom = - d;

			light.shadow.camera.near = 2;
			light.shadow.camera.far = 50;

			light.shadow.mapSize.x = 1024;
			light.shadow.mapSize.y = 1024;

			scene.add( light );

			stats = new Stats();
			stats.domElement.style.position = 'absolute';
			stats.domElement.style.top = '0px';
			container.appendChild( stats.domElement );

			//

			window.addEventListener( 'resize', onWindowResize );

		}

		function initPhysics() {

			// Physics configuration

			collisionConfiguration = new Ammo.btSoftBodyRigidBodyCollisionConfiguration();
			dispatcher = new Ammo.btCollisionDispatcher( collisionConfiguration );
			broadphase = new Ammo.btDbvtBroadphase();
			solver = new Ammo.btSequentialImpulseConstraintSolver();
			softBodySolver = new Ammo.btDefaultSoftBodySolver();
			physicsWorld = new Ammo.btSoftRigidDynamicsWorld( dispatcher, broadphase, solver, collisionConfiguration, softBodySolver );
			physicsWorld.setGravity( new Ammo.btVector3( 0, gravityConstant, 0 ) );
			physicsWorld.getWorldInfo().set_m_gravity( new Ammo.btVector3( 0, gravityConstant, 0 ) );

			transformAux1 = new Ammo.btTransform();

		}

		function createObjects() {

			const pos = new THREE.Vector3();
			const quat = new THREE.Quaternion();

			// Ground
			pos.set( 0, - 0.5, 0 );
			quat.set( 0, 0, 0, 1 );
			const ground = createParalellepiped( 40, 1, 40, 0, pos, quat, new THREE.MeshPhongMaterial( { color: 0xFFFFFF } ) );
			ground.castShadow = true;
			ground.receiveShadow = true;
			textureLoader.load( 'textures/grid.png', function ( texture ) {

				texture.colorSpace = THREE.SRGBColorSpace;
				texture.wrapS = THREE.RepeatWrapping;
				texture.wrapT = THREE.RepeatWrapping;
				texture.repeat.set( 40, 40 );
				ground.material.map = texture;
				ground.material.needsUpdate = true;

			} );


			// Ball
			const ballMass = 1.2;
			const ballRadius = 0.6;

			const ball = new THREE.Mesh( new THREE.SphereGeometry( ballRadius, 20, 20 ), new THREE.MeshPhongMaterial( { color: 0x202020 } ) );
			ball.castShadow = true;
			ball.receiveShadow = true;
			const ballShape = new Ammo.btSphereShape( ballRadius );
			ballShape.setMargin( margin );
			pos.set( - 3, 2, 0 );
			quat.set( 0, 0, 0, 1 );
			createRigidBody( ball, ballShape, ballMass, pos, quat );
			ball.userData.physicsBody.setFriction( 0.5 );

			// Wall
			const brickMass = 0.5;
			const brickLength = 1.2;
			const brickDepth = 0.6;
			const brickHeight = brickLength * 0.5;
			const numBricksLength = 6;
			const numBricksHeight = 8;
			const z0 = - numBricksLength * brickLength * 0.5;
			pos.set( 0, brickHeight * 0.5, z0 );
			quat.set( 0, 0, 0, 1 );

			for ( let j = 0; j < numBricksHeight; j ++ ) {

				const oddRow = ( j % 2 ) == 1;

				pos.z = z0;

				if ( oddRow ) {

					pos.z -= 0.25 * brickLength;

				}

				const nRow = oddRow ? numBricksLength + 1 : numBricksLength;

				for ( let i = 0; i < nRow; i ++ ) {

					let brickLengthCurrent = brickLength;
					let brickMassCurrent = brickMass;
					if ( oddRow && ( i == 0 || i == nRow - 1 ) ) {

						brickLengthCurrent *= 0.5;
						brickMassCurrent *= 0.5;

					}

					const brick = createParalellepiped( brickDepth, brickHeight, brickLengthCurrent, brickMassCurrent, pos, quat, createMaterial() );
					brick.castShadow = true;
					brick.receiveShadow = true;

					if ( oddRow && ( i == 0 || i == nRow - 2 ) ) {

						pos.z += 0.75 * brickLength;

					} else {

						pos.z += brickLength;

					}

				}

				pos.y += brickHeight;

			}

			// The rope
			// Rope graphic object
			const ropeNumSegments = 10;
			const ropeLength = 4;
			const ropeMass = 3;
			const ropePos = ball.position.clone();
			ropePos.y += ballRadius;

			const segmentLength = ropeLength / ropeNumSegments;
			const ropeGeometry = new THREE.BufferGeometry();
			const ropeMaterial = new THREE.LineBasicMaterial( { color: 0x000000 } );
			const ropePositions = [];
			const ropeIndices = [];

			for ( let i = 0; i < ropeNumSegments + 1; i ++ ) {

				ropePositions.push( ropePos.x, ropePos.y + i * segmentLength, ropePos.z );

			}

			for ( let i = 0; i < ropeNumSegments; i ++ ) {

				ropeIndices.push( i, i + 1 );

			}

			ropeGeometry.setIndex( new THREE.BufferAttribute( new Uint16Array( ropeIndices ), 1 ) );
			ropeGeometry.setAttribute( 'position', new THREE.BufferAttribute( new Float32Array( ropePositions ), 3 ) );
			ropeGeometry.computeBoundingSphere();
			rope = new THREE.LineSegments( ropeGeometry, ropeMaterial );
			rope.castShadow = true;
			rope.receiveShadow = true;
			scene.add( rope );

			// Rope physic object
			const softBodyHelpers = new Ammo.btSoftBodyHelpers();
			const ropeStart = new Ammo.btVector3( ropePos.x, ropePos.y, ropePos.z );
			const ropeEnd = new Ammo.btVector3( ropePos.x, ropePos.y + ropeLength, ropePos.z );
			const ropeSoftBody = softBodyHelpers.CreateRope( physicsWorld.getWorldInfo(), ropeStart, ropeEnd, ropeNumSegments - 1, 0 );
			const sbConfig = ropeSoftBody.get_m_cfg();
			sbConfig.set_viterations( 10 );
			sbConfig.set_piterations( 10 );
			ropeSoftBody.setTotalMass( ropeMass, false );
			Ammo.castObject( ropeSoftBody, Ammo.btCollisionObject ).getCollisionShape().setMargin( margin * 3 );
			physicsWorld.addSoftBody( ropeSoftBody, 1, - 1 );
			rope.userData.physicsBody = ropeSoftBody;
			// Disable deactivation
			ropeSoftBody.setActivationState( 4 );

			// The base
			const armMass = 2;
			const armLength = 3;
			const pylonHeight = ropePos.y + ropeLength;
			const baseMaterial = new THREE.MeshPhongMaterial( { color: 0x606060 } );
			pos.set( ropePos.x, 0.1, ropePos.z - armLength );
			quat.set( 0, 0, 0, 1 );
			const base = createParalellepiped( 1, 0.2, 1, 0, pos, quat, baseMaterial );
			base.castShadow = true;
			base.receiveShadow = true;
			pos.set( ropePos.x, 0.5 * pylonHeight, ropePos.z - armLength );
			const pylon = createParalellepiped( 0.4, pylonHeight, 0.4, 0, pos, quat, baseMaterial );
			pylon.castShadow = true;
			pylon.receiveShadow = true;
			pos.set( ropePos.x, pylonHeight + 0.2, ropePos.z - 0.5 * armLength );
			const arm = createParalellepiped( 0.4, 0.4, armLength + 0.4, armMass, pos, quat, baseMaterial );
			arm.castShadow = true;
			arm.receiveShadow = true;

			// Glue the rope extremes to the ball and the arm
			const influence = 1;
			ropeSoftBody.appendAnchor( 0, ball.userData.physicsBody, true, influence );
			ropeSoftBody.appendAnchor( ropeNumSegments, arm.userData.physicsBody, true, influence );

			// Hinge constraint to move the arm
			const pivotA = new Ammo.btVector3( 0, pylonHeight * 0.5, 0 );
			const pivotB = new Ammo.btVector3( 0, - 0.2, - armLength * 0.5 );
			const axis = new Ammo.btVector3( 0, 1, 0 );
			hinge = new Ammo.btHingeConstraint( pylon.userData.physicsBody, arm.userData.physicsBody, pivotA, pivotB, axis, axis, true );
			physicsWorld.addConstraint( hinge, true );


		}

		function createParalellepiped( sx, sy, sz, mass, pos, quat, material ) {

			const threeObject = new THREE.Mesh( new THREE.BoxGeometry( sx, sy, sz, 1, 1, 1 ), material );
			const shape = new Ammo.btBoxShape( new Ammo.btVector3( sx * 0.5, sy * 0.5, sz * 0.5 ) );
			shape.setMargin( margin );

			createRigidBody( threeObject, shape, mass, pos, quat );

			return threeObject;

		}

		function createRigidBody( threeObject, physicsShape, mass, pos, quat ) {

			threeObject.position.copy( pos );
			threeObject.quaternion.copy( quat );

			const transform = new Ammo.btTransform();
			transform.setIdentity();
			transform.setOrigin( new Ammo.btVector3( pos.x, pos.y, pos.z ) );
			transform.setRotation( new Ammo.btQuaternion( quat.x, quat.y, quat.z, quat.w ) );
			const motionState = new Ammo.btDefaultMotionState( transform );

			const localInertia = new Ammo.btVector3( 0, 0, 0 );
			physicsShape.calculateLocalInertia( mass, localInertia );

			const rbInfo = new Ammo.btRigidBodyConstructionInfo( mass, motionState, physicsShape, localInertia );
			const body = new Ammo.btRigidBody( rbInfo );

			threeObject.userData.physicsBody = body;

			scene.add( threeObject );

			if ( mass > 0 ) {

				rigidBodies.push( threeObject );

				// Disable deactivation
				body.setActivationState( 4 );

			}

			physicsWorld.addRigidBody( body );

		}

		function createRandomColor() {

			return Math.floor( Math.random() * ( 1 << 24 ) );

		}

		function createMaterial() {

			return new THREE.MeshPhongMaterial( { color: createRandomColor() } );

		}

		function initInput() {

			window.addEventListener( 'keydown', function ( event ) {

				switch ( event.keyCode ) {

					// Q
					case 81:
						armMovement = 1;
						break;

					// A
					case 65:
						armMovement = - 1;
						break;

				}

			} );

			window.addEventListener( 'keyup', function () {

				armMovement = 0;

			} );

		}

		function onWindowResize() {

			camera.aspect = window.innerWidth / window.innerHeight;
			camera.updateProjectionMatrix();

			renderer.setSize( window.innerWidth, window.innerHeight );

		}

		function animate() {

			render();
			stats.update();

		}

		function render() {

			const deltaTime = clock.getDelta();

			updatePhysics( deltaTime );

			renderer.render( scene, camera );

		}

		function updatePhysics( deltaTime ) {

			// Hinge control
			hinge.enableAngularMotor( true, 1.5 * armMovement, 50 );

			// Step world
			physicsWorld.stepSimulation( deltaTime, 10 );

			// Update rope
			const softBody = rope.userData.physicsBody;
			const ropePositions = rope.geometry.attributes.position.array;
			const numVerts = ropePositions.length / 3;
			const nodes = softBody.get_m_nodes();
			let indexFloat = 0;

			for ( let i = 0; i < numVerts; i ++ ) {

				const node = nodes.at( i );
				const nodePos = node.get_m_x();
				ropePositions[ indexFloat ++ ] = nodePos.x();
				ropePositions[ indexFloat ++ ] = nodePos.y();
				ropePositions[ indexFloat ++ ] = nodePos.z();

			}

			rope.geometry.attributes.position.needsUpdate = true;

			// Update rigid bodies
			for ( let i = 0, il = rigidBodies.length; i < il; i ++ ) {

				const objThree = rigidBodies[ i ];
				const objPhys = objThree.userData.physicsBody;
				const ms = objPhys.getMotionState();
				if ( ms ) {

					ms.getWorldTransform( transformAux1 );
					const p = transformAux1.getOrigin();
					const q = transformAux1.getRotation();
					objThree.position.set( p.x(), p.y(), p.z() );
					objThree.quaternion.set( q.x(), q.y(), q.z(), q.w() );

				}

			}

		}

		</script>

	</body>
</html>