text: /*
   * Copyright (C) 2007 Apple Inc.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
   * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
   */
  
  function createVector(x,y,z) {
      return new Array(x,y,z);
  }
  
  function sqrLengthVector(self) {
      return self[0] * self[0] + self[1] * self[1] + self[2] * self[2];
  }
  
  function lengthVector(self) {
      return Math.sqrt(self[0] * self[0] + self[1] * self[1] + self[2] * self[2]);
  }
  
  function addVector(self, v) {
      self[0] += v[0];
      self[1] += v[1];
      self[2] += v[2];
      return self;
  }
  
  function subVector(self, v) {
      self[0] -= v[0];
      self[1] -= v[1];
      self[2] -= v[2];
      return self;
  }
  
  function scaleVector(self, scale) {
      self[0] *= scale;
      self[1] *= scale;
      self[2] *= scale;
      return self;
  }
  
  function normaliseVector(self) {
      var len = Math.sqrt(self[0] * self[0] + self[1] * self[1] + self[2] * self[2]);
      self[0] /= len;
      self[1] /= len;
      self[2] /= len;
      return self;
  }
  
  function add(v1, v2) {
      return new Array(v1[0] + v2[0], v1[1] + v2[1], v1[2] + v2[2]);
  }
  
  function sub(v1, v2) {
      return new Array(v1[0] - v2[0], v1[1] - v2[1], v1[2] - v2[2]);
  }
  
  function scalev(v1, v2) {
      return new Array(v1[0] * v2[0], v1[1] * v2[1], v1[2] * v2[2]);
  }
  
  function dot(v1, v2) {
      return v1[0] * v2[0] + v1[1] * v2[1] + v1[2] * v2[2];
  }
  
  function scale(v, scale) {
      return [v[0] * scale, v[1] * scale, v[2] * scale];
  }
  
  function cross(v1, v2) {
      return [v1[1] * v2[2] - v1[2] * v2[1], 
              v1[2] * v2[0] - v1[0] * v2[2],
              v1[0] * v2[1] - v1[1] * v2[0]];
  
  }
  
  function normalise(v) {
      var len = lengthVector(v);
      return [v[0] / len, v[1] / len, v[2] / len];
  }
  
  function transformMatrix(self, v) {
      var vals = self;
      var x  = vals[0] * v[0] + vals[1] * v[1] + vals[2] * v[2] + vals[3];
      var y  = vals[4] * v[0] + vals[5] * v[1] + vals[6] * v[2] + vals[7];
      var z  = vals[8] * v[0] + vals[9] * v[1] + vals[10] * v[2] + vals[11];
      return [x, y, z];
  }
  
  function invertMatrix(self) {
      var temp = new Array(16);
      var tx = -self[3];
      var ty = -self[7];
      var tz = -self[11];
      for (h = 0; h < 3; h++) 
          for (v = 0; v < 3; v++) 
              temp[h + v * 4] = self[v + h * 4];
      for (i = 0; i < 11; i++)
          self[i] = temp[i];
      self[3] = tx * self[0] + ty * self[1] + tz * self[2];
      self[7] = tx * self[4] + ty * self[5] + tz * self[6];
      self[11] = tx * self[8] + ty * self[9] + tz * self[10];
      return self;
  }
  
  
  // Triangle intersection using barycentric coord method
  function Triangle(p1, p2, p3) {
      var edge1 = sub(p3, p1);
      var edge2 = sub(p2, p1);
      var normal = cross(edge1, edge2);
      if (Math.abs(normal[0]) > Math.abs(normal[1]))
          if (Math.abs(normal[0]) > Math.abs(normal[2]))
              this.axis = 0; 
          else 
              this.axis = 2;
      else
          if (Math.abs(normal[1]) > Math.abs(normal[2])) 
              this.axis = 1;
          else 
              this.axis = 2;
      var u = (this.axis + 1) % 3;
      var v = (this.axis + 2) % 3;
      var u1 = edge1[u];
      var v1 = edge1[v];
      
      var u2 = edge2[u];
      var v2 = edge2[v];
      this.normal = normalise(normal);
      this.nu = normal[u] / normal[this.axis];
      this.nv = normal[v] / normal[this.axis];
      this.nd = dot(normal, p1) / normal[this.axis];
      var det = u1 * v2 - v1 * u2;
      this.eu = p1[u];
      this.ev = p1[v]; 
      this.nu1 = u1 / det;
      this.nv1 = -v1 / det;
      this.nu2 = v2 / det;
      this.nv2 = -u2 / det; 
      this.material = [0.7, 0.7, 0.7];
  }
  
  Triangle.prototype.intersect = function(orig, dir, near, far) {
      var u = (this.axis + 1) % 3;
      var v = (this.axis + 2) % 3;
      var d = dir[this.axis] + this.nu * dir[u] + this.nv * dir[v];
      var t = (this.nd - orig[this.axis] - this.nu * orig[u] - this.nv * orig[v]) / d;
      if (t < near || t > far)
          return null;
      var Pu = orig[u] + t * dir[u] - this.eu;
      var Pv = orig[v] + t * dir[v] - this.ev;
      var a2 = Pv * this.nu1 + Pu * this.nv1;
      if (a2 < 0) 
          return null;
      var a3 = Pu * this.nu2 + Pv * this.nv2;
      if (a3 < 0) 
          return null;
  
      if ((a2 + a3) > 1) 
          return null;
      return t;
  }
  
  function Scene(a_triangles) {
      this.triangles = a_triangles;
      this.lights = [];
      this.ambient = [0,0,0];
      this.background = [0.8,0.8,1];
  }
  var zero = new Array(0,0,0);
  
  Scene.prototype.intersect = function(origin, dir, near, far) {
      var closest = null;
      for (i = 0; i < this.triangles.length; i++) {
          var triangle = this.triangles[i];   
          var d = triangle.intersect(origin, dir, near, far);
          if (d == null || d > far || d < near)
              continue;
          far = d;
          closest = triangle;
      }
      
      if (!closest)
          return [this.background[0],this.background[1],this.background[2]];
          
      var normal = closest.normal;
      var hit = add(origin, scale(dir, far)); 
      if (dot(dir, normal) > 0)
          normal = [-normal[0], -normal[1], -normal[2]];
      
      var colour = null;
      if (closest.shader) {
          colour = closest.shader(closest, hit, dir);
      } else {
          colour = closest.material;
      }
      
      // do reflection
      var reflected = null;
      if (colour.reflection > 0.001) {
          var reflection = addVector(scale(normal, -2*dot(dir, normal)), dir);
          reflected = this.intersect(hit, reflection, 0.0001, 1000000);
          if (colour.reflection >= 0.999999)
              return reflected;
      }
      
      var l = [this.ambient[0], this.ambient[1], this.ambient[2]];
      for (var i = 0; i < this.lights.length; i++) {
          var light = this.lights[i];
          var toLight = sub(light, hit);
          var distance = lengthVector(toLight);
          scaleVector(toLight, 1.0/distance);
          distance -= 0.0001;
          if (this.blocked(hit, toLight, distance))
              continue;
          var nl = dot(normal, toLight);
          if (nl > 0)
              addVector(l, scale(light.colour, nl));
      }
      l = scalev(l, colour);
      if (reflected) {
          l = addVector(scaleVector(l, 1 - colour.reflection), scaleVector(reflected, colour.reflection));
      }
      return l;
  }
  
  Scene.prototype.blocked = function(O, D, far) {
      var near = 0.0001;
      var closest = null;
      for (i = 0; i < this.triangles.length; i++) {
          var triangle = this.triangles[i];   
          var d = triangle.intersect(O, D, near, far);
          if (d == null || d > far || d < near)
              continue;
          return true;
      }
      
      return false;
  }
  
  
  // this camera code is from notes i made ages ago, it is from *somewhere* -- i cannot remember where
  // that somewhere is
  function Camera(origin, lookat, up) {
      var zaxis = normaliseVector(subVector(lookat, origin));
      var xaxis = normaliseVector(cross(up, zaxis));
      var yaxis = normaliseVector(cross(xaxis, subVector([0,0,0], zaxis)));
      var m = new Array(16);
      m[0] = xaxis[0]; m[1] = xaxis[1]; m[2] = xaxis[2];
      m[4] = yaxis[0]; m[5] = yaxis[1]; m[6] = yaxis[2];
      m[8] = zaxis[0]; m[9] = zaxis[1]; m[10] = zaxis[2];
      invertMatrix(m);
      m[3] = 0; m[7] = 0; m[11] = 0;
      this.origin = origin;
      this.directions = new Array(4);
      this.directions[0] = normalise([-0.7,  0.7, 1]);
      this.directions[1] = normalise([ 0.7,  0.7, 1]);
      this.directions[2] = normalise([ 0.7, -0.7, 1]);
      this.directions[3] = normalise([-0.7, -0.7, 1]);
      this.directions[0] = transformMatrix(m, this.directions[0]);
      this.directions[1] = transformMatrix(m, this.directions[1]);
      this.directions[2] = transformMatrix(m, this.directions[2]);
      this.directions[3] = transformMatrix(m, this.directions[3]);
  }
  
  Camera.prototype.generateRayPair = function(y) {
      rays = new Array(new Object(), new Object());
      rays[0].origin = this.origin;
      rays[1].origin = this.origin;
      rays[0].dir = addVector(scale(this.directions[0], y), scale(this.directions[3], 1 - y));
      rays[1].dir = addVector(scale(this.directions[1], y), scale(this.directions[2], 1 - y));
      return rays;
  }
  
  function renderRows(camera, scene, pixels, width, height, starty, stopy) {
      for (var y = starty; y < stopy; y++) {
          var rays = camera.generateRayPair(y / height);
          for (var x = 0; x < width; x++) {
              var xp = x / width;
              var origin = addVector(scale(rays[0].origin, xp), scale(rays[1].origin, 1 - xp));
              var dir = normaliseVector(addVector(scale(rays[0].dir, xp), scale(rays[1].dir, 1 - xp)));
              var l = scene.intersect(origin, dir);
              pixels[y][x] = l;
          }
      }
  }
  
  Camera.prototype.render = function(scene, pixels, width, height) {
      var cam = this;
      var row = 0;
      renderRows(cam, scene, pixels, width, height, 0, height);
  }
  
  
  
  function raytraceScene()
  {
      var startDate = new Date().getTime();
      var numTriangles = 2 * 6;
      var triangles = new Array();//numTriangles);
      var tfl = createVector(-10,  10, -10);
      var tfr = createVector( 10,  10, -10);
      var tbl = createVector(-10,  10,  10);
      var tbr = createVector( 10,  10,  10);
      var bfl = createVector(-10, -10, -10);
      var bfr = createVector( 10, -10, -10);
      var bbl = createVector(-10, -10,  10);
      var bbr = createVector( 10, -10,  10);
      
      // cube!!!
      // front
      var i = 0;
      
      triangles[i++] = new Triangle(tfl, tfr, bfr);
      triangles[i++] = new Triangle(tfl, bfr, bfl);
      // back
      triangles[i++] = new Triangle(tbl, tbr, bbr);
      triangles[i++] = new Triangle(tbl, bbr, bbl);
      //        triangles[i-1].material = [0.7,0.2,0.2];
      //            triangles[i-1].material.reflection = 0.8;
      // left
      triangles[i++] = new Triangle(tbl, tfl, bbl);
      //            triangles[i-1].reflection = 0.6;
      triangles[i++] = new Triangle(tfl, bfl, bbl);
      //            triangles[i-1].reflection = 0.6;
      // right
      triangles[i++] = new Triangle(tbr, tfr, bbr);
      triangles[i++] = new Triangle(tfr, bfr, bbr);
      // top
      triangles[i++] = new Triangle(tbl, tbr, tfr);
      triangles[i++] = new Triangle(tbl, tfr, tfl);
      // bottom
      triangles[i++] = new Triangle(bbl, bbr, bfr);
      triangles[i++] = new Triangle(bbl, bfr, bfl);
      
      //Floor!!!!
      var green = createVector(0.0, 0.4, 0.0);
      var grey = createVector(0.4, 0.4, 0.4);
      grey.reflection = 1.0;
      var floorShader = function(tri, pos, view) {
          var x = ((pos[0]/32) % 2 + 2) % 2;
          var z = ((pos[2]/32 + 0.3) % 2 + 2) % 2;
          if (x < 1 != z < 1) {
              //in the real world we use the fresnel term...
              //    var angle = 1-dot(view, tri.normal);
              //   angle *= angle;
              //  angle *= angle;
              // angle *= angle;
              //grey.reflection = angle;
              return grey;
          } else 
              return green;
      }
      var ffl = createVector(-1000, -30, -1000);
      var ffr = createVector( 1000, -30, -1000);
      var fbl = createVector(-1000, -30,  1000);
      var fbr = createVector( 1000, -30,  1000);
      triangles[i++] = new Triangle(fbl, fbr, ffr);
      triangles[i-1].shader = floorShader;
      triangles[i++] = new Triangle(fbl, ffr, ffl);
      triangles[i-1].shader = floorShader;
      
      var _scene = new Scene(triangles);
      _scene.lights[0] = createVector(20, 38, -22);
      _scene.lights[0].colour = createVector(0.7, 0.3, 0.3);
      _scene.lights[1] = createVector(-23, 40, 17);
      _scene.lights[1].colour = createVector(0.7, 0.3, 0.3);
      _scene.lights[2] = createVector(23, 20, 17);
      _scene.lights[2].colour = createVector(0.7, 0.7, 0.7);
      _scene.ambient = createVector(0.1, 0.1, 0.1);
      //  _scene.background = createVector(0.7, 0.7, 1.0);
      
      var size = 30;
      var pixels = new Array();
      for (var y = 0; y < size; y++) {
          pixels[y] = new Array();
          for (var x = 0; x < size; x++) {
              pixels[y][x] = 0;
          }
      }
  
      var _camera = new Camera(createVector(-40, 40, 40), createVector(0, 0, 0), createVector(0, 1, 0));
      _camera.render(_scene, pixels, size, size);
  
      return pixels;
  }
  
  function arrayToCanvasCommands(pixels)
  {
      var s = '<canvas id="renderCanvas" width="30px" height="30px"></canvas><scr' + 'ipt>\nvar pixels = [';
      var size = 30;
      for (var y = 0; y < size; y++) {
          s += "[";
          for (var x = 0; x < size; x++) {
              s += "[" + pixels[y][x] + "],";
          }
          s+= "],";
      }
      s += '];\n    var canvas = document.getElementById("renderCanvas").getContext("2d");\n\
  \n\
  \n\
      var size = 30;\n\
      canvas.fillStyle = "red";\n\
      canvas.fillRect(0, 0, size, size);\n\
      canvas.scale(1, -1);\n\
      canvas.translate(0, -size);\n\
  \n\
      if (!canvas.setFillColor)\n\
          canvas.setFillColor = function(r, g, b, a) {\n\
              this.fillStyle = "rgb("+[Math.floor(r * 255), Math.floor(g * 255), Math.floor(b * 255)]+")";\n\
      }\n\
  \n\
  for (var y = 0; y < size; y++) {\n\
    for (var x = 0; x < size; x++) {\n\
      var l = pixels[y][x];\n\
      canvas.setFillColor(l[0], l[1], l[2], 1);\n\
      canvas.fillRect(x, y, 1, 1);\n\
    }\n\
  }</scr' + 'ipt>';
  
      return s;
  }
  
  testOutput = arrayToCanvasCommands(raytraceScene());
  