example.js

var gl;

function initGL(canvas) {
  try {
    gl = canvas.getContext('experimental-webgl');
    gl.viewportWidth = canvas.width;
    gl.viewportHeight = canvas.height;
  } catch (e) {
  }
  if (!gl) {
    alert('Could not initialise WebGL, sorry :-(');
  }
}


function getShader(gl, id) {
  var shaderScript = document.getElementById(id);
  if (!shaderScript) {
    return null;
  }

  var str = '';
  var k = shaderScript.firstChild;
  while (k) {
    if (k.nodeType == 3) {
      str += k.textContent;
    }
    k = k.nextSibling;
  }

  var shader;
  if (shaderScript.type == 'x-shader/x-fragment') {
    shader = gl.createShader(gl.FRAGMENT_SHADER);
  } else if (shaderScript.type == 'x-shader/x-vertex') {
    shader = gl.createShader(gl.VERTEX_SHADER);
  } else {
    return null;
  }

  gl.shaderSource(shader, str);
  gl.compileShader(shader);

  if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
    alert(gl.getShaderInfoLog(shader));
    return null;
  }

  return shader;
}


var shaderProgram;

function initShaders() {
  var fragmentShader = getShader(gl, 'shader-fs');
  var vertexShader = getShader(gl, 'shader-vs');

  shaderProgram = gl.createProgram();
  gl.attachShader(shaderProgram, vertexShader);
  gl.attachShader(shaderProgram, fragmentShader);
  gl.linkProgram(shaderProgram);

  if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
    alert('Could not initialise shaders');
  }

  gl.useProgram(shaderProgram);

  shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, 'aVertexPosition');
  gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);

  shaderProgram.vertexColorAttribute = gl.getAttribLocation(shaderProgram, 'aVertexColor');
  gl.enableVertexAttribArray(shaderProgram.vertexColorAttribute);

  shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, 'uPMatrix');
  shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, 'uMVMatrix');
}


var mvMatrix = mat4.create();
var mvMatrixStack = [];
var pMatrix = mat4.create();

function mvPushMatrix() {
  var copy = mat4.create();
  mat4.set(mvMatrix, copy);
  mvMatrixStack.push(copy);
}

function mvPopMatrix() {
  if (mvMatrixStack.length == 0) {
    throw 'Invalid popMatrix!';
  }
  mvMatrix = mvMatrixStack.pop();
}


function setMatrixUniforms() {
  gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
  gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
}


function degToRad(degrees) {
  return degrees * Math.PI / 180;
}


var pyramidVertexPositionBuffer;
var pyramidVertexColorBuffer;
var cubeVertexPositionBuffer;
var cubeVertexColorBuffer;
var cubeVertexIndexBuffer;

function initBuffers() {
  pyramidVertexPositionBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexPositionBuffer);
  var vertices = [
    // Front face
    0.0,  1.0,  0.0,
    -1.0, -1.0,  1.0,
    1.0, -1.0,  1.0,

    // Right face
    0.0,  1.0,  0.0,
    1.0, -1.0,  1.0,
    1.0, -1.0, -1.0,

    // Back face
    0.0,  1.0,  0.0,
    1.0, -1.0, -1.0,
    -1.0, -1.0, -1.0,

    // Left face
    0.0,  1.0,  0.0,
    -1.0, -1.0, -1.0,
    -1.0, -1.0,  1.0
  ];
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
  pyramidVertexPositionBuffer.itemSize = 3;
  pyramidVertexPositionBuffer.numItems = 12;

  pyramidVertexColorBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexColorBuffer);
  var colors = [
    // Front face
    1.0, 0.0, 0.0, 1.0,
    0.0, 1.0, 0.0, 1.0,
    0.0, 0.0, 1.0, 1.0,

    // Right face
    1.0, 0.0, 0.0, 1.0,
    0.0, 0.0, 1.0, 1.0,
    0.0, 1.0, 0.0, 1.0,

    // Back face
    1.0, 0.0, 0.0, 1.0,
    0.0, 1.0, 0.0, 1.0,
    0.0, 0.0, 1.0, 1.0,

    // Left face
    1.0, 0.0, 0.0, 1.0,
    0.0, 0.0, 1.0, 1.0,
    0.0, 1.0, 0.0, 1.0
  ];
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
  pyramidVertexColorBuffer.itemSize = 4;
  pyramidVertexColorBuffer.numItems = 12;


  cubeVertexPositionBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
  vertices = [
    // Front face
    -1.0, -1.0,  1.0,
    1.0, -1.0,  1.0,
    1.0,  1.0,  1.0,
    -1.0,  1.0,  1.0,

    // Back face
    -1.0, -1.0, -1.0,
    -1.0,  1.0, -1.0,
    1.0,  1.0, -1.0,
    1.0, -1.0, -1.0,

    // Top face
    -1.0,  1.0, -1.0,
    -1.0,  1.0,  1.0,
    1.0,  1.0,  1.0,
    1.0,  1.0, -1.0,

    // Bottom face
    -1.0, -1.0, -1.0,
    1.0, -1.0, -1.0,
    1.0, -1.0,  1.0,
    -1.0, -1.0,  1.0,

    // Right face
    1.0, -1.0, -1.0,
    1.0,  1.0, -1.0,
    1.0,  1.0,  1.0,
    1.0, -1.0,  1.0,

    // Left face
    -1.0, -1.0, -1.0,
    -1.0, -1.0,  1.0,
    -1.0,  1.0,  1.0,
    -1.0,  1.0, -1.0
  ];
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
  cubeVertexPositionBuffer.itemSize = 3;
  cubeVertexPositionBuffer.numItems = 24;

  cubeVertexColorBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexColorBuffer);
  colors = [
    [1.0, 0.0, 0.0, 1.0], // Front face
    [1.0, 1.0, 0.0, 1.0], // Back face
    [0.0, 1.0, 0.0, 1.0], // Top face
    [1.0, 0.5, 0.5, 1.0], // Bottom face
    [1.0, 0.0, 1.0, 1.0], // Right face
    [0.0, 0.0, 1.0, 1.0]  // Left face
  ];
  var unpackedColors = [];
  for (var i in colors) {
    var color = colors[i];
    for (var j=0; j < 4; j++) {
      unpackedColors = unpackedColors.concat(color);
    }
  }
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(unpackedColors), gl.STATIC_DRAW);
  cubeVertexColorBuffer.itemSize = 4;
  cubeVertexColorBuffer.numItems = 24;

  cubeVertexIndexBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
  var cubeVertexIndices = [
    0, 1, 2,      0, 2, 3,    // Front face
    4, 5, 6,      4, 6, 7,    // Back face
    8, 9, 10,     8, 10, 11,  // Top face
    12, 13, 14,   12, 14, 15, // Bottom face
    16, 17, 18,   16, 18, 19, // Right face
    20, 21, 22,   20, 22, 23  // Left face
  ];
  gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
  cubeVertexIndexBuffer.itemSize = 1;
  cubeVertexIndexBuffer.numItems = 36;
}


var rPyramid = 0;
var rCube = 0;

function drawScene() {
  gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
  gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

  mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);

  mat4.identity(mvMatrix);

  mat4.translate(mvMatrix, [-1.5, 0.0, -8.0]);

  mvPushMatrix();
  mat4.rotate(mvMatrix, degToRad(rPyramid), [0, 1, 0]);

  gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexPositionBuffer);
  gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, pyramidVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

  gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexColorBuffer);
  gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, pyramidVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

  setMatrixUniforms();
  gl.drawArrays(gl.TRIANGLES, 0, pyramidVertexPositionBuffer.numItems);

  mvPopMatrix();


  mat4.translate(mvMatrix, [3.0, 0.0, 0.0]);

  mvPushMatrix();
  mat4.rotate(mvMatrix, degToRad(rCube), [1, 1, 1]);

  gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
  gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, cubeVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

  gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexColorBuffer);
  gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, cubeVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
  setMatrixUniforms();
  gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);

  mvPopMatrix();

}


var lastTime = 0;

function animate() {
  var timeNow = new Date().getTime();
  if (lastTime != 0) {
    var elapsed = timeNow - lastTime;

    rPyramid += (90 * elapsed) / 1000.0;
    rCube -= (75 * elapsed) / 1000.0;
  }
  lastTime = timeNow;
}


function tick() {
  requestAnimFrame(tick);
  drawScene();
  animate();
}


function webGLStart() {
  var canvas = document.getElementById('lesson04-canvas');
  initGL(canvas);
  initShaders()
  initBuffers();

  gl.clearColor(0.0, 0.0, 0.0, 1.0);
  gl.enable(gl.DEPTH_TEST);

  tick();
}