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<!DOCTYPE html>

<html>
<head>
  <title>Javascript Racer - v1 (straight)</title>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
  <link href="common.css" rel="stylesheet" type="text/css" />
</head>

<body>
  <table id="controls">
    <tr>
      <td colspan="2">
        <a href='v1.straight.html'>straight</a> |
        <a href='v2.curves.html'>curves</a> |
        <a href='v3.hills.html'>hills</a> |
        <a href='v4.final.html'>final</a>
      </td>
    </tr>
    <tr><td id="fps" colspan="2" align="right"></td></tr>
    <tr>
      <th><label for="resolution">Resolution :</label></th>
      <td>
        <select id="resolution" style="width:100%">
          <option value='fine'>Fine (1280x960)</option>
          <option selected value='high'>High (1024x768)</option>
          <option value='medium'>Medium (640x480)</option>
          <option value='low'>Low (480x360)</option>
        </select>
      </td>
    </tr>
    <tr>
      <th><label for="lanes">Lanes :</label></th>
      <td>
        <select id="lanes">
          <option>1</option>
          <option>2</option>
          <option selected>3</option>
          <option>4</option>
        </select>
      </td>
    </tr>
    <tr>
      <th><label for="roadWidth">Road Width (<span id="currentRoadWidth"></span>) :</label></th>
      <td><input id="roadWidth" type='range' min='500' max='3000' title="integer (500-3000)"></td>
    </tr>
    <tr>
      <th><label for="cameraHeight">CameraHeight (<span id="currentCameraHeight"></span>) :</label></th>
      <td><input id="cameraHeight" type='range' min='500' max='5000' title="integer (500-5000)"></td>
    </tr>
    <tr>
      <th><label for="drawDistance">Draw Distance (<span id="currentDrawDistance"></span>) :</label></th>
      <td><input id="drawDistance" type='range' min='100' max='500' title="integer (100-500)"></td>
    </tr>
    <tr>
      <th><label for="fieldOfView">Field of View (<span id="currentFieldOfView"></span>) :</label></th>
      <td><input id="fieldOfView" type='range' min='80' max='140' title="integer (80-140)"></td>
    </tr>
    <tr>
      <th><label for="fogDensity">Fog Density (<span id="currentFogDensity"></span>) :</label></th>
      <td><input id="fogDensity" type='range' min='0' max='50' title="integer (0-50)"></td>
    </tr>
  </table>

  <div id='instructions'>
    <p>Use the <b>arrow keys</b> to drive the car.</p>
  </div>
  <div id="racer">
    <canvas id="canvas">
      Sorry, this example cannot be run because your browser does not support the &lt;canvas&gt; element
    </canvas>
    Loading...
  </div>

  <audio id='music'>
    <source src="music/racer.ogg">
    <source src="music/racer.mp3">
  </audio>
  <span id="mute"></span>

  <script src="stats.js"></script>
  <script src="common.js"></script>
  <script>

    var fps = 60; // how many 'update' frames per second
    var step = 1/fps; // how long is each frame (in seconds)
    var width = 1024; // logical canvas width
    var height = 768; // logical canvas height
    var segments = []; // array of road segments
    var stats = Game.stats('fps'); // mr.doobs FPS counter
    var canvas = Dom.get('canvas'); // our canvas...
    var ctx = canvas.getContext('2d'); // ...and its drawing context
    var background = null; // our background image (loaded below)
    var sprites = null; // our spritesheet (loaded below)
    var resolution = null; // scaling factor to provide resolution independence (computed)
    var roadWidth = 2000; // actually half the roads width, easier math if the road spans from -roadWidth to +roadWidth
    var segmentLength = 200; // length of a single segment
    var rumbleLength = 3; // number of segments per red/white rumble strip
    var trackLength = null; // z length of entire track (computed)
    var lanes = 3; // number of lanes
    var fieldOfView = 100; // angle (degrees) for field of view
    var cameraHeight = 1000; // z height of camera
    var cameraDepth = null; // z distance camera is from screen (computed)
    var drawDistance = 300; // number of segments to draw
    var playerX = 0; // player x offset from center of road (-1 to 1 to stay independent of roadWidth)
    var playerZ = null; // player relative z distance from camera (computed)
    var fogDensity = 5; // exponential fog density
    var position = 0; // current camera Z position (add playerZ to get player's absolute Z position)
    var speed = 0; // current speed
    var maxSpeed = segmentLength/step; // top speed (ensure we can't move more than 1 segment in a single frame to make collision detection easier)
    var accel = maxSpeed/5; // acceleration rate - tuned until it 'felt' right
    var breaking = -maxSpeed; // deceleration rate when braking
    var decel = -maxSpeed/5; // 'natural' deceleration rate when neither accelerating, nor braking
    var offRoadDecel = -maxSpeed/2; // off road deceleration is somewhere in between
    var offRoadLimit = maxSpeed/4; // limit when off road deceleration no longer applies (e.g. you can always go at least this speed even when off road)

    var keyLeft = false;
    var keyRight = false;
    var keyFaster = false;
    var keySlower = false;

    //=========================================================================
    // UPDATE THE GAME WORLD
    //=========================================================================

    function update(dt) {

      position = Util.increase(position, dt * speed, trackLength);

      var dx = dt * 2 * (speed/maxSpeed); // at top speed, should be able to cross from left to right (-1 to 1) in 1 second

      if (keyLeft)
        playerX = playerX - dx;
      else if (keyRight)
        playerX = playerX + dx;

      if (keyFaster)
        speed = Util.accelerate(speed, accel, dt);
      else if (keySlower)
        speed = Util.accelerate(speed, breaking, dt);
      else
        speed = Util.accelerate(speed, decel, dt);

      if (((playerX < -1) || (playerX > 1)) && (speed > offRoadLimit))
        speed = Util.accelerate(speed, offRoadDecel, dt);

      playerX = Util.limit(playerX, -2, 2); // dont ever let player go too far out of bounds
      speed = Util.limit(speed, 0, maxSpeed); // or exceed maxSpeed

    }

    //=========================================================================
    // RENDER THE GAME WORLD
    //=========================================================================

    function render() {

      var baseSegment = findSegment(position);
      var maxy = height;

      ctx.clearRect(0, 0, width, height);

      Render.background(ctx, background, width, height, BACKGROUND.SKY);
      Render.background(ctx, background, width, height, BACKGROUND.HILLS);
      Render.background(ctx, background, width, height, BACKGROUND.TREES);

      var n, segment;

      for(n = 0 ; n < drawDistance ; n++) {

        segment = segments[(baseSegment.index + n) % segments.length];
        segment.looped = segment.index < baseSegment.index;
        segment.fog = Util.exponentialFog(n/drawDistance, fogDensity);

        Util.project(segment.p1, (playerX * roadWidth), cameraHeight, position - (segment.looped ? trackLength : 0), cameraDepth, width, height, roadWidth);
        Util.project(segment.p2, (playerX * roadWidth), cameraHeight, position - (segment.looped ? trackLength : 0), cameraDepth, width, height, roadWidth);

        if ((segment.p1.camera.z <= cameraDepth) || // behind us
            (segment.p2.screen.y >= maxy)) // clip by (already rendered) segment
          continue;

        Render.segment(ctx, width, lanes,
                       segment.p1.screen.x,
                       segment.p1.screen.y,
                       segment.p1.screen.w,
                       segment.p2.screen.x,
                       segment.p2.screen.y,
                       segment.p2.screen.w,
                       segment.fog,
                       segment.color);

        maxy = segment.p2.screen.y;
      }

      Render.player(ctx, width, height, resolution, roadWidth, sprites, speed/maxSpeed,
                    cameraDepth/playerZ,
                    width/2,
                    height,
                    speed * (keyLeft ? -1 : keyRight ? 1 : 0),
                    0);
    }

    //=========================================================================
    // BUILD ROAD GEOMETRY
    //=========================================================================

    function resetRoad() {
      segments = [];
      for(var n = 0 ; n < 500 ; n++) {
        segments.push({
           index: n,
           p1: { world: { z: n *segmentLength }, camera: {}, screen: {} },
           p2: { world: { z: (n+1)*segmentLength }, camera: {}, screen: {} },
           color: Math.floor(n/rumbleLength)%2 ? COLORS.DARK : COLORS.LIGHT
        });
      }

      segments[findSegment(playerZ).index + 2].color = COLORS.START;
      segments[findSegment(playerZ).index + 3].color = COLORS.START;
      for(var n = 0 ; n < rumbleLength ; n++)
        segments[segments.length-1-n].color = COLORS.FINISH;

      trackLength = segments.length * segmentLength;
    }

    function findSegment(z) {
      return segments[Math.floor(z/segmentLength) % segments.length];
    }

    //=========================================================================
    // THE GAME LOOP
    //=========================================================================

    Game.run({
      canvas: canvas, render: render, update: update, stats: stats, step: step,
      images: ["background", "sprites"],
      keys: [
        { keys: [KEY.LEFT, KEY.A], mode: 'down', action: function() { keyLeft = true; } },
        { keys: [KEY.RIGHT, KEY.D], mode: 'down', action: function() { keyRight = true; } },
        { keys: [KEY.UP, KEY.W], mode: 'down', action: function() { keyFaster = true; } },
        { keys: [KEY.DOWN, KEY.S], mode: 'down', action: function() { keySlower = true; } },
        { keys: [KEY.LEFT, KEY.A], mode: 'up', action: function() { keyLeft = false; } },
        { keys: [KEY.RIGHT, KEY.D], mode: 'up', action: function() { keyRight = false; } },
        { keys: [KEY.UP, KEY.W], mode: 'up', action: function() { keyFaster = false; } },
        { keys: [KEY.DOWN, KEY.S], mode: 'up', action: function() { keySlower = false; } }
      ],
      ready: function(images) {
        background = images[0];
        sprites = images[1];
        reset();
      }
    });

    function reset(options) {
      /*
options = options || {};
canvas.width = width = Util.toInt(options.width, width);
canvas.height = height = Util.toInt(options.height, height);
lanes = Util.toInt(options.lanes, lanes);
roadWidth = Util.toInt(options.roadWidth, roadWidth);
cameraHeight = Util.toInt(options.cameraHeight, cameraHeight);
drawDistance = Util.toInt(options.drawDistance, drawDistance);
fogDensity = Util.toInt(options.fogDensity, fogDensity);
fieldOfView = Util.toInt(options.fieldOfView, fieldOfView);
segmentLength = Util.toInt(options.segmentLength, segmentLength);
rumbleLength = Util.toInt(options.rumbleLength, rumbleLength);
cameraDepth = 1 / Math.tan((fieldOfView/2) * Math.PI/180);
playerZ = (cameraHeight * cameraDepth);
resolution = height/480;
refreshTweakUI();
*/
      options = options || {};
      canvas.width = width = Util.toInt(options.width, width);
      canvas.height = height = Util.toInt(options.height, height);
      lanes = Util.toInt(options.lanes, lanes);
      roadWidth = Util.toInt(options.roadWidth, roadWidth);
      cameraHeight = Util.toInt(options.cameraHeight, cameraHeight);
      drawDistance = Util.toInt(options.drawDistance, drawDistance);
      fogDensity = Util.toInt(options.fogDensity, fogDensity);
      fieldOfView = Util.toInt(options.fieldOfView, fieldOfView);
      segmentLength = Util.toInt(options.segmentLength, segmentLength);
      rumbleLength = Util.toInt(options.rumbleLength, rumbleLength);
      cameraDepth = 1 / Math.tan((fieldOfView/2) * Math.PI/180);
      playerZ = (cameraHeight * cameraDepth);
      resolution = height/480;


      if ((segments.length==0) || (options.segmentLength) || (options.rumbleLength))
        resetRoad(); // only rebuild road when necessary
    }

    //=========================================================================
    // TWEAK UI HANDLERS
    //=========================================================================

    Dom.on('resolution', 'change', function(ev) {
      var w, h, ratio;
      switch(ev.target.options[ev.target.selectedIndex].value) {
        case 'fine': w = 1280; h = 960; ratio=w/width; break;
        case 'high': w = 1024; h = 768; ratio=w/width; break;
        case 'medium': w = 640; h = 480; ratio=w/width; break;
        case 'low': w = 480; h = 360; ratio=w/width; break;
      }
      reset({ width: w, height: h })
      Dom.blur(ev);
    });
    
    Dom.on('lanes', 'change', function(ev) { Dom.blur(ev); reset({ lanes: ev.target.options[ev.target.selectedIndex].value }); });
    Dom.on('roadWidth', 'change', function(ev) { Dom.blur(ev); reset({ roadWidth: Util.limit(Util.toInt(ev.target.value), Util.toInt(ev.target.getAttribute('min')), Util.toInt(ev.target.getAttribute('max'))) }); });
    Dom.on('cameraHeight', 'change', function(ev) { Dom.blur(ev); reset({ cameraHeight: Util.limit(Util.toInt(ev.target.value), Util.toInt(ev.target.getAttribute('min')), Util.toInt(ev.target.getAttribute('max'))) }); });
    Dom.on('drawDistance', 'change', function(ev) { Dom.blur(ev); reset({ drawDistance: Util.limit(Util.toInt(ev.target.value), Util.toInt(ev.target.getAttribute('min')), Util.toInt(ev.target.getAttribute('max'))) }); });
    Dom.on('fieldOfView', 'change', function(ev) { Dom.blur(ev); reset({ fieldOfView: Util.limit(Util.toInt(ev.target.value), Util.toInt(ev.target.getAttribute('min')), Util.toInt(ev.target.getAttribute('max'))) }); });
    Dom.on('fogDensity', 'change', function(ev) { Dom.blur(ev); reset({ fogDensity: Util.limit(Util.toInt(ev.target.value), Util.toInt(ev.target.getAttribute('min')), Util.toInt(ev.target.getAttribute('max'))) }); });

    function refreshTweakUI() {
      Dom.get('lanes').selectedIndex = lanes-1;
      Dom.get('currentRoadWidth').innerHTML = Dom.get('roadWidth').value = roadWidth;
      Dom.get('currentCameraHeight').innerHTML = Dom.get('cameraHeight').value = cameraHeight;
      Dom.get('currentDrawDistance').innerHTML = Dom.get('drawDistance').value = drawDistance;
      Dom.get('currentFieldOfView').innerHTML = Dom.get('fieldOfView').value = fieldOfView;
      Dom.get('currentFogDensity').innerHTML = Dom.get('fogDensity').value = fogDensity;
    }

    //=========================================================================

  </script>

</body>

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