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

  <script type="module">
    import * as v3d from '../build/v3d.module.js';

    import Stats from './jsm/libs/stats.module.js';

    import { OrbitControls } from './jsm/controls/OrbitControls.js';

    // Graphics variables
    let container, stats;
    let camera, controls, scene, renderer;
    let textureLoader;
    const clock = new v3d.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();
      animate();

    });

    function init() {

      initGraphics();

      initPhysics();

      createObjects();

      initInput();

    }

    function initGraphics() {

      container = document.getElementById('container');

      camera = new v3d.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 0.2, 2000);

      scene = new v3d.Scene();
      scene.background = new v3d.Color(0xbfd1e5);

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

      renderer = new v3d.WebGLRenderer();
      renderer.setPixelRatio(window.devicePixelRatio);
      renderer.setSize(window.innerWidth, window.innerHeight);
      renderer.shadowMap.enabled = true;
      container.appendChild(renderer.domElement);

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

      textureLoader = new v3d.TextureLoader();

      const ambientLight = new v3d.AmbientLight(0x404040);
      scene.add(ambientLight);

      const light = new v3d.DirectionalLight(0xffffff, 1);
      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, false);

    }

    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 v3d.Vector3();
      const quat = new v3d.Quaternion();

      // Ground
      pos.set(0, - 0.5, 0);
      quat.set(0, 0, 0, 1);
      const ground = createParalellepiped(40, 1, 40, 0, pos, quat, new v3d.MeshPhongMaterial({ color: 0xFFFFFF }));
      ground.castShadow = true;
      ground.receiveShadow = true;
      textureLoader.load("textures/grid.png", function(texture) {

        texture.wrapS = v3d.RepeatWrapping;
        texture.wrapT = v3d.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 v3d.Mesh(new v3d.SphereBufferGeometry(ballRadius, 20, 20), new v3d.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 v3d.BufferGeometry();
      const ropeMaterial = new v3d.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 v3d.BufferAttribute(new Uint16Array(ropeIndices), 1));
      ropeGeometry.setAttribute('position', new v3d.BufferAttribute(new Float32Array(ropePositions), 3));
      ropeGeometry.computeBoundingSphere();
      rope = new v3d.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 v3d.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 v3d.Mesh(new v3d.BoxBufferGeometry(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 v3d.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;

        }

      }, false);

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

        armMovement = 0;

      }, false);

    }

    function onWindowResize() {

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

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

    }

    function animate() {

      requestAnimationFrame(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>