planck-js/example/OneSidedPlatform.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.
 */

planck.testbed('OneSidedPlatform', function(testbed) {
  var pl = planck, Vec2 = pl.Vec2;
  var world = new pl.World(Vec2(0, -10));

  var radius = 0.5;
  var top = 10.0 + 0.5;
  var bottom = 10.0 - 0.5;

  var UNKNOWN = 0, ABOVE = +1, BELOW = -1;

  var state = UNKNOWN;

  // Ground
  var ground = world.createBody();
  ground.createFixture(pl.Edge(Vec2(-20.0, 0.0), Vec2(20.0, 0.0)), 0.0);

  // Platform
  var platform = world.createBody(Vec2(0.0, 10.0));
  var platformFix = platform.createFixture(pl.Box(3.0, 0.5), 0.0);

  // Actor
  var character = world.createDynamicBody(Vec2(0.0, 12.0));
  var characterFix = character.createFixture(pl.Circle(radius), 20.0);
  character.setLinearVelocity(Vec2(0.0, -50.0));

  world.on('pre-solve', function(contact, oldManifold) {
    var fixA = contact.getFixtureA();
    var fixB = contact.getFixtureB();

    var isCharPlatformContact =
      fixA === platformFix && fixB === characterFix ||
      fixB === platformFix && fixA === characterFix;

    if (!isCharPlatformContact) {
      return;
    }

    if (0) {
      var p = character.getPosition();

      if (p.y < top + radius - 3.0 * /*linearSlop*/ 0.005) {
        contact.setEnabled(false);
      }
    } else {
      var v = character.getLinearVelocity();
      if (v.y > 0.0) {
        contact.setEnabled(false);
      }
    }
  });

  testbed.step = function(settings) {
    var v = character.getLinearVelocity();
    testbed.status("Character Linear Velocity", v.y);
  };

  return world;
});