planck-js/example/Car.js

2D JavaScript physics engine for cross-platform HTML5 game development

/*
 * MIT License
 * Copyright (c) 2019 Erin Catto
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

// This is a fun demo that shows off the wheel joint
planck.testbed('Car', function(testbed) {

  testbed.speed = 1.3;
  testbed.hz = 50;

  var pl = planck, Vec2 = pl.Vec2;
  var world = new pl.World({
    gravity : Vec2(0, -10)
  });

  // wheel spring settings
  var HZ = 4.0;
  var ZETA = 0.7;
  var SPEED = 50.0;

  var ground = world.createBody();

  var groundFD = {
    density : 0.0,
    friction : 0.6
  };

  ground.createFixture(pl.Edge(Vec2(-20.0, 0.0), Vec2(20.0, 0.0)), groundFD);

  var hs = [ 0.25, 1.0, 4.0, 0.0, 0.0, -1.0, -2.0, -2.0, -1.25, 0.0 ];

  var x = 20.0, y1 = 0.0, dx = 5.0;

  for (var i = 0; i < 10; ++i) {
    var y2 = hs[i];
    ground.createFixture(pl.Edge(Vec2(x, y1), Vec2(x + dx, y2)), groundFD);
    y1 = y2;
    x += dx;
  }

  for (var i = 0; i < 10; ++i) {
    var y2 = hs[i];
    ground.createFixture(pl.Edge(Vec2(x, y1), Vec2(x + dx, y2)), groundFD);
    y1 = y2;
    x += dx;
  }

  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x + 40.0, 0.0)), groundFD);

  x += 80.0;
  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x + 40.0, 0.0)), groundFD);

  x += 40.0;
  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x + 10.0, 5.0)), groundFD);

  x += 20.0;
  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x + 40.0, 0.0)), groundFD);

  x += 40.0;
  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x, 20.0)), groundFD);

  // Teeter
  var teeter = world.createDynamicBody(Vec2(140.0, 1.0));
  teeter.createFixture(pl.Box(10.0, 0.25), 1.0);
  world.createJoint(pl.RevoluteJoint({
    lowerAngle : -8.0 * Math.PI / 180.0,
    upperAngle : 8.0 * Math.PI / 180.0,
    enableLimit : true
  }, ground, teeter, teeter.getPosition()));

  teeter.applyAngularImpulse(100.0, true);

  // Bridge
  var bridgeFD = {};
  bridgeFD.density = 1.0;
  bridgeFD.friction = 0.6;

  var prevBody = ground;
  for (var i = 0; i < 20; ++i) {
    var bridgeBlock = world.createDynamicBody(Vec2(161.0 + 2.0 * i, -0.125));
    bridgeBlock.createFixture(pl.Box(1.0, 0.125), bridgeFD);

    world.createJoint(pl.RevoluteJoint({}, prevBody, bridgeBlock, Vec2(160.0 + 2.0 * i, -0.125)));

    prevBody = bridgeBlock;
  }

  world.createJoint(pl.RevoluteJoint({}, prevBody, ground, Vec2(160.0 + 2.0 * i, -0.125)));

  // Boxes
  var box = pl.Box(0.5, 0.5);

  world.createDynamicBody(Vec2(230.0, 0.5))
    .createFixture(box, 0.5);

  world.createDynamicBody(Vec2(230.0, 1.5))
    .createFixture(box, 0.5);

  world.createDynamicBody(Vec2(230.0, 2.5))
    .createFixture(box, 0.5);

  world.createDynamicBody(Vec2(230.0, 3.5))
    .createFixture(box, 0.5);

  world.createDynamicBody(Vec2(230.0, 4.5))
    .createFixture(box, 0.5);

  // Car
  var car = world.createDynamicBody(Vec2(0.0, 1.0));
  car.createFixture(pl.Polygon([
    Vec2(-1.5, -0.5),
    Vec2(1.5, -0.5),
    Vec2(1.5, 0.0),
    Vec2(0.0, 0.9),
    Vec2(-1.15, 0.9),
    Vec2(-1.5, 0.2)
  ]), 1.0);

  var wheelFD = {};
  wheelFD.density = 1.0;
  wheelFD.friction = 0.9;

  var wheelBack = world.createDynamicBody(Vec2(-1.0, 0.35));
  wheelBack.createFixture(pl.Circle(0.4), wheelFD);

  var wheelFront = world.createDynamicBody(Vec2(1.0, 0.4));
  wheelFront.createFixture(pl.Circle(0.4), wheelFD);

  var springBack = world.createJoint(pl.WheelJoint({
    motorSpeed : 0.0,
    maxMotorTorque : 20.0,
    enableMotor : true,
    frequencyHz : HZ,
    dampingRatio : ZETA
  }, car, wheelBack, wheelBack.getPosition(), Vec2(0.0, 1.0)));

  var springFront = world.createJoint(pl.WheelJoint({
    motorSpeed : 0.0,
    maxMotorTorque : 10.0,
    enableMotor : false,
    frequencyHz : HZ,
    dampingRatio : ZETA
  }, car, wheelFront, wheelFront.getPosition(), Vec2(0.0, 1.0)));

  testbed.keydown = function() {
    if (testbed.activeKeys.down) {
      HZ = Math.max(0.0, HZ - 1.0);
      springBack.setSpringFrequencyHz(HZ);
      springFront.setSpringFrequencyHz(HZ);

    } else if (testbed.activeKeys.up) {
      HZ += 1.0;
      springBack.setSpringFrequencyHz(HZ);
      springFront.setSpringFrequencyHz(HZ);
    }
  };

  testbed.step = function() {
    if (testbed.activeKeys.right && testbed.activeKeys.left) {
      springBack.setMotorSpeed(0);
      springBack.enableMotor(true);

    } else if (testbed.activeKeys.right) {
      springBack.setMotorSpeed(-SPEED);
      springBack.enableMotor(true);

    } else if (testbed.activeKeys.left) {
      springBack.setMotorSpeed(+SPEED);
      springBack.enableMotor(true);

    } else {
      springBack.setMotorSpeed(0);
      springBack.enableMotor(false);
    }

    var cp = car.getPosition();
    if (cp.x > testbed.x + 10) {
      testbed.x = cp.x - 10;

    } else if (cp.x < testbed.x - 10) {
      testbed.x = cp.x + 10;
    }
  };

  testbed.info('←/→: Accelerate car, ↑/↓: Change spring frequency');

  return world;
});