使用物理引擎为三维场景增加物理效果

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

        var collisionConfiguration = new Ammo.btSoftBodyRigidBodyCollisionConfiguration();
        var dispatcher = new Ammo.btCollisionDispatcher( collisionConfiguration );
        var broadphase = new Ammo.btDbvtBroadphase();
        var solver = new Ammo.btSequentialImpulseConstraintSolver();
        var 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 ) );

        pos.set( 0, - 0.5, 0 );
        quat.set( 0, 0, 0, 1 );
        var 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.wrapS = THREE.RepeatWrapping;
          texture.wrapT = THREE.RepeatWrapping;
          texture.repeat.set( 80, 80 );
          ground.material.map = texture;
          ground.material.needsUpdate = true;
        } );

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

        var threeObject = new THREE.Mesh( new THREE.BoxGeometry( sx, sy, sz, 1, 1, 1 ), material );
        var 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 );

        var 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 ) );
        var motionState = new Ammo.btDefaultMotionState( transform );

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

        var rbInfo = new Ammo.btRigidBodyConstructionInfo( mass, motionState, physicsShape, localInertia );
        var 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 );

          return body;
      }

          raycaster.setFromCamera( mouseCoords, camera );

          // Creates a ball
          var ballMass = 3;
          var ballRadius = 0.4;

          var ball = new THREE.Mesh( new THREE.SphereGeometry( ballRadius, 18, 16 ), createRendomColorObjectMeatrial() );
          ball.castShadow = true;
          ball.receiveShadow = true;
          var ballShape = new Ammo.btSphereShape( ballRadius );
          ballShape.setMargin( margin );
          pos.copy( raycaster.ray.direction );
          pos.add( raycaster.ray.origin );
          quat.set( 0, 0, 0, 1 );
          var ballBody = createRigidBody( ball, ballShape, ballMass, pos, quat );
          ballBody.setFriction( 0.5 );

          pos.copy( raycaster.ray.direction );
          pos.multiplyScalar( 14 );
          ballBody.setLinearVelocity( new Ammo.btVector3( pos.x, pos.y, pos.z ) );

          clickRequest = false;

      function animate() {

        requestAnimationFrame( animate );

        render();
        stats.update();

      }

      function render() {

        var deltaTime = clock.getDelta();

        updatePhysics( deltaTime );

        processClick();

        renderer.render( scene, camera );

      }

      function updatePhysics( deltaTime ) {

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

        // Update soft volumes
        for ( var i = 0, il = softBodies.length; i < il; i++ ) {
          var volume = softBodies[ i ];
          var geometry = volume.geometry;
          var softBody = volume.userData.physicsBody;
          var volumePositions = geometry.attributes.position.array;
          var volumeNormals = geometry.attributes.normal.array;
          var association = geometry.ammoIndexAssociation;
          var numVerts = association.length;
          var nodes = softBody.get_m_nodes();
          for ( var j = 0; j < numVerts; j ++ ) {

            var node = nodes.at( j );
            var nodePos = node.get_m_x();
            var x = nodePos.x();
            var y = nodePos.y();
            var z = nodePos.z();
            var nodeNormal = node.get_m_n();
            var nx = nodeNormal.x();
            var ny = nodeNormal.y();
            var nz = nodeNormal.z();

            var assocVertex = association[ j ];

            for ( var k = 0, kl = assocVertex.length; k < kl; k++ ) {
              var indexVertex = assocVertex[ k ];
              volumePositions[ indexVertex ] = x;
              volumeNormals[ indexVertex ] = nx;
              indexVertex++;
              volumePositions[ indexVertex ] = y;
              volumeNormals[ indexVertex ] = ny;
              indexVertex++;
              volumePositions[ indexVertex ] = z;
              volumeNormals[ indexVertex ] = nz;
            }
          }

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

        }

        // Update rigid bodies
        for ( var i = 0, il = rigidBodies.length; i < il; i++ ) {
          var objThree = rigidBodies[ i ];
          var objPhys = objThree.userData.physicsBody;
          var ms = objPhys.getMotionState();
          if ( ms ) {

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

          }
        }

      }