Lab 2

lab2/README.md

+# Lab2 IHM
+
+* **docs**: contains the lab's statement
+* **libs**: contains WebGL libraries and utilities
+* **src**: contains the source code of the lab2 that you should complete (`main()` function in **lab2.js** file)
+* **DO NOT CHANGE** the name of the file `lab2.html`, however, you are free to change its content.

lab2/lib/cuon-utils.js

+// cuon-utils.js (c) 2012 kanda and matsuda
+/**
+ * Create a program object and make current
+ * @param gl GL context
+ * @param vshader a vertex shader program (string)
+ * @param fshader a fragment shader program (string)
+ * @return true, if the program object was created and successfully made current 
+ */
+function initShaders(gl, vshader, fshader) {
+  var program = createProgram(gl, vshader, fshader);
+  if (!program) {
+    console.log('Failed to create program');
+    return false;
+  }
+
+  gl.useProgram(program);
+  gl.program = program;
+
+  return true;
+}
+
+/**
+ * Create the linked program object
+ * @param gl GL context
+ * @param vshader a vertex shader program (string)
+ * @param fshader a fragment shader program (string)
+ * @return created program object, or null if the creation has failed
+ */
+function createProgram(gl, vshader, fshader) {
+  // Create shader object
+  var vertexShader = loadShader(gl, gl.VERTEX_SHADER, vshader);
+  var fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fshader);
+  if (!vertexShader || !fragmentShader) {
+    return null;
+  }
+
+  // Create a program object
+  var program = gl.createProgram();
+  if (!program) {
+    return null;
+  }
+
+  // Attach the shader objects
+  gl.attachShader(program, vertexShader);
+  gl.attachShader(program, fragmentShader);
+
+  // Link the program object
+  gl.linkProgram(program);
+
+  // Check the result of linking
+  var linked = gl.getProgramParameter(program, gl.LINK_STATUS);
+  if (!linked) {
+    var error = gl.getProgramInfoLog(program);
+    console.log('Failed to link program: ' + error);
+    gl.deleteProgram(program);
+    gl.deleteShader(fragmentShader);
+    gl.deleteShader(vertexShader);
+    return null;
+  }
+  return program;
+}
+
+/**
+ * Create a shader object
+ * @param gl GL context
+ * @param type the type of the shader object to be created
+ * @param source shader program (string)
+ * @return created shader object, or null if the creation has failed.
+ */
+function loadShader(gl, type, source) {
+  // Create shader object
+  var shader = gl.createShader(type);
+  if (shader == null) {
+    console.log('unable to create shader');
+    return null;
+  }
+
+  // Set the shader program
+  gl.shaderSource(shader, source);
+
+  // Compile the shader
+  gl.compileShader(shader);
+
+  // Check the result of compilation
+  var compiled = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
+  if (!compiled) {
+    var error = gl.getShaderInfoLog(shader);
+    console.log('Failed to compile shader: ' + error);
+    gl.deleteShader(shader);
+    return null;
+  }
+
+  return shader;
+}
+
+/** 
+ * Initialize and get the rendering for WebglInstance
+ * @param canvas <cavnas> element
+ * @param opt_debug flag to initialize the context for debugging
+ * @return the rendering context for WebglInstance
+ */
+function getWebGLContext(canvas, opt_debug) {
+  // Get the rendering context for WebglInstance
+  var gl = WebGLUtils.setupWebGL(canvas);
+  if (!gl) return null;
+
+  // if opt_debug is explicitly false, create the context for debugging
+  if (arguments.length < 2 || opt_debug) {
+    gl = WebGLDebugUtils.makeDebugContext(gl);
+  }
+
+  return gl;
+}

lab2/lib/webgl-debug.js

+//Copyright (c) 2009 The Chromium Authors. All rights reserved.
+//Use of this source code is governed by a BSD-style license that can be
+//found in the LICENSE file.
+
+// Various functions for helping debug WebglInstance apps.
+
+WebGLDebugUtils = function() {
+
+/**
+ * Wrapped logging function.
+ * @param {string} msg Message to log.
+ */
+var log = function(msg) {
+  if (window.console && window.console.log) {
+    window.console.log(msg);
+  }
+};
+
+/**
+ * Which arguements are enums.
+ * @type {!Object.<number, string>}
+ */
+var glValidEnumContexts = {
+
+  // Generic setters and getters
+
+  'enable': { 0:true },
+  'disable': { 0:true },
+  'getParameter': { 0:true },
+
+  // Rendering
+
+  'drawArrays': { 0:true },
+  'drawElements': { 0:true, 2:true },
+
+  // Shaders
+
+  'createShader': { 0:true },
+  'getShaderParameter': { 1:true },
+  'getProgramParameter': { 1:true },
+
+  // Vertex attributes
+
+  'getVertexAttrib': { 1:true },
+  'vertexAttribPointer': { 2:true },
+
+  // Textures
+
+  'bindTexture': { 0:true },
+  'activeTexture': { 0:true },
+  'getTexParameter': { 0:true, 1:true },
+  'texParameterf': { 0:true, 1:true },
+  'texParameteri': { 0:true, 1:true, 2:true },
+  'texImage2D': { 0:true, 2:true, 6:true, 7:true },
+  'texSubImage2D': { 0:true, 6:true, 7:true },
+  'copyTexImage2D': { 0:true, 2:true },
+  'copyTexSubImage2D': { 0:true },
+  'generateMipmap': { 0:true },
+
+  // Buffer objects
+
+  'bindBuffer': { 0:true },
+  'bufferData': { 0:true, 2:true },
+  'bufferSubData': { 0:true },
+  'getBufferParameter': { 0:true, 1:true },
+
+  // Renderbuffers and framebuffers
+
+  'pixelStorei': { 0:true, 1:true },
+  'readPixels': { 4:true, 5:true },
+  'bindRenderbuffer': { 0:true },
+  'bindFramebuffer': { 0:true },
+  'checkFramebufferStatus': { 0:true },
+  'framebufferRenderbuffer': { 0:true, 1:true, 2:true },
+  'framebufferTexture2D': { 0:true, 1:true, 2:true },
+  'getFramebufferAttachmentParameter': { 0:true, 1:true, 2:true },
+  'getRenderbufferParameter': { 0:true, 1:true },
+  'renderbufferStorage': { 0:true, 1:true },
+
+  // Frame buffer operations (clear, blend, depth test, stencil)
+
+  'clear': { 0:true },
+  'depthFunc': { 0:true },
+  'blendFunc': { 0:true, 1:true },
+  'blendFuncSeparate': { 0:true, 1:true, 2:true, 3:true },
+  'blendEquation': { 0:true },
+  'blendEquationSeparate': { 0:true, 1:true },
+  'stencilFunc': { 0:true },
+  'stencilFuncSeparate': { 0:true, 1:true },
+  'stencilMaskSeparate': { 0:true },
+  'stencilOp': { 0:true, 1:true, 2:true },
+  'stencilOpSeparate': { 0:true, 1:true, 2:true, 3:true },
+
+  // Culling
+
+  'cullFace': { 0:true },
+  'frontFace': { 0:true },
+};
+
+/**
+ * Map of numbers to names.
+ * @type {Object}
+ */
+var glEnums = null;
+
+/**
+ * Initializes this module. Safe to call more than once.
+ * @param {!WebGLRenderingContext} ctx A WebglInstance context. If
+ *    you have more than one context it doesn't matter which one
+ *    you pass in, it is only used to pull out constants.
+ */
+function init(ctx) {
+  if (glEnums == null) {
+    glEnums = { };
+    for (var propertyName in ctx) {
+      if (typeof ctx[propertyName] == 'number') {
+        glEnums[ctx[propertyName]] = propertyName;
+      }
+    }
+  }
+}
+
+/**
+ * Checks the utils have been initialized.
+ */
+function checkInit() {
+  if (glEnums == null) {
+    throw 'WebGLDebugUtils.init(ctx) not called';
+  }
+}
+
+/**
+ * Returns true or false if value matches any WebglInstance enum
+ * @param {*} value Value to check if it might be an enum.
+ * @return {boolean} True if value matches one of the WebglInstance defined enums
+ */
+function mightBeEnum(value) {
+  checkInit();
+  return (glEnums[value] !== undefined);
+}
+
+/**
+ * Gets an string version of an WebglInstance enum.
+ *
+ * Example:
+ *   var str = WebGLDebugUtil.glEnumToString(ctx.getError());
+ *
+ * @param {number} value Value to return an enum for
+ * @return {string} The string version of the enum.
+ */
+function glEnumToString(value) {
+  checkInit();
+  var name = glEnums[value];
+  return (name !== undefined) ? name :
+      ("*UNKNOWN WebglInstance ENUM (0x" + value.toString(16) + ")");
+}
+
+/**
+ * Returns the string version of a WebglInstance argument.
+ * Attempts to convert enum arguments to strings.
+ * @param {string} functionName the name of the WebglInstance function.
+ * @param {number} argumentIndx the index of the argument.
+ * @param {*} value The value of the argument.
+ * @return {string} The value as a string.
+ */
+function glFunctionArgToString(functionName, argumentIndex, value) {
+  var funcInfo = glValidEnumContexts[functionName];
+  if (funcInfo !== undefined) {
+    if (funcInfo[argumentIndex]) {
+      return glEnumToString(value);
+    }
+  }
+  return value.toString();
+}
+
+/**
+ * Given a WebglInstance context returns a wrapped context that calls
+ * gl.getError after every command and calls a function if the
+ * result is not gl.NO_ERROR.
+ *
+ * @param {!WebGLRenderingContext} ctx The webgl context to
+ *        wrap.
+ * @param {!function(err, funcName, args): void} opt_onErrorFunc
+ *        The function to call when gl.getError returns an
+ *        error. If not specified the default function calls
+ *        console.log with a message.
+ */
+function makeDebugContext(ctx, opt_onErrorFunc) {
+  init(ctx);
+  opt_onErrorFunc = opt_onErrorFunc || function(err, functionName, args) {
+        // apparently we can't do args.join(",");
+        var argStr = "";
+        for (var ii = 0; ii < args.length; ++ii) {
+          argStr += ((ii == 0) ? '' : ', ') +
+              glFunctionArgToString(functionName, ii, args[ii]);
+        }
+        log("WebglInstance error "+ glEnumToString(err) + " in "+ functionName +
+            "(" + argStr + ")");
+      };
+
+  // Holds booleans for each GL error so after we get the error ourselves
+  // we can still return it to the client app.
+  var glErrorShadow = { };
+
+  // Makes a function that calls a WebglInstance function and then calls getError.
+  function makeErrorWrapper(ctx, functionName) {
+    return function() {
+      var result = ctx[functionName].apply(ctx, arguments);
+      var err = ctx.getError();
+      if (err != 0) {
+        glErrorShadow[err] = true;
+        opt_onErrorFunc(err, functionName, arguments);
+      }
+      return result;
+    };
+  }
+
+  // Make a an object that has a copy of every property of the WebglInstance context
+  // but wraps all functions.
+  var wrapper = {};
+  for (var propertyName in ctx) {
+    if (typeof ctx[propertyName] == 'function') {
+       wrapper[propertyName] = makeErrorWrapper(ctx, propertyName);
+     } else {
+       wrapper[propertyName] = ctx[propertyName];
+     }
+  }
+
+  // Override the getError function with one that returns our saved results.
+  wrapper.getError = function() {
+    for (var err in glErrorShadow) {
+      if (glErrorShadow[err]) {
+        glErrorShadow[err] = false;
+        return err;
+      }
+    }
+    return ctx.NO_ERROR;
+  };
+
+  return wrapper;
+}
+
+function resetToInitialState(ctx) {
+  var numAttribs = ctx.getParameter(ctx.MAX_VERTEX_ATTRIBS);
+  var tmp = ctx.createBuffer();
+  ctx.bindBuffer(ctx.ARRAY_BUFFER, tmp);
+  for (var ii = 0; ii < numAttribs; ++ii) {
+    ctx.disableVertexAttribArray(ii);
+    ctx.vertexAttribPointer(ii, 4, ctx.FLOAT, false, 0, 0);
+    ctx.vertexAttrib1f(ii, 0);
+  }
+  ctx.deleteBuffer(tmp);
+
+  var numTextureUnits = ctx.getParameter(ctx.MAX_TEXTURE_IMAGE_UNITS);
+  for (var ii = 0; ii < numTextureUnits; ++ii) {
+    ctx.activeTexture(ctx.TEXTURE0 + ii);
+    ctx.bindTexture(ctx.TEXTURE_CUBE_MAP, null);
+    ctx.bindTexture(ctx.TEXTURE_2D, null);
+  }
+
+  ctx.activeTexture(ctx.TEXTURE0);
+  ctx.useProgram(null);
+  ctx.bindBuffer(ctx.ARRAY_BUFFER, null);
+  ctx.bindBuffer(ctx.ELEMENT_ARRAY_BUFFER, null);
+  ctx.bindFramebuffer(ctx.FRAMEBUFFER, null);
+  ctx.bindRenderbuffer(ctx.RENDERBUFFER, null);
+  ctx.disable(ctx.BLEND);
+  ctx.disable(ctx.CULL_FACE);
+  ctx.disable(ctx.DEPTH_TEST);
+  ctx.disable(ctx.DITHER);
+  ctx.disable(ctx.SCISSOR_TEST);
+  ctx.blendColor(0, 0, 0, 0);
+  ctx.blendEquation(ctx.FUNC_ADD);
+  ctx.blendFunc(ctx.ONE, ctx.ZERO);
+  ctx.clearColor(0, 0, 0, 0);
+  ctx.clearDepth(1);
+  ctx.clearStencil(-1);
+  ctx.colorMask(true, true, true, true);
+  ctx.cullFace(ctx.BACK);
+  ctx.depthFunc(ctx.LESS);
+  ctx.depthMask(true);
+  ctx.depthRange(0, 1);
+  ctx.frontFace(ctx.CCW);
+  ctx.hint(ctx.GENERATE_MIPMAP_HINT, ctx.DONT_CARE);
+  ctx.lineWidth(1);
+  ctx.pixelStorei(ctx.PACK_ALIGNMENT, 4);
+  ctx.pixelStorei(ctx.UNPACK_ALIGNMENT, 4);
+  ctx.pixelStorei(ctx.UNPACK_FLIP_Y_WEBGL, false);
+  ctx.pixelStorei(ctx.UNPACK_PREMULTIPLY_ALPHA_WEBGL, false);
+  // TODO: Delete this IF.
+  if (ctx.UNPACK_COLORSPACE_CONVERSION_WEBGL) {
+    ctx.pixelStorei(ctx.UNPACK_COLORSPACE_CONVERSION_WEBGL, ctx.BROWSER_DEFAULT_WEBGL);
+  }
+  ctx.polygonOffset(0, 0);
+  ctx.sampleCoverage(1, false);
+  ctx.scissor(0, 0, ctx.canvas.width, ctx.canvas.height);
+  ctx.stencilFunc(ctx.ALWAYS, 0, 0xFFFFFFFF);
+  ctx.stencilMask(0xFFFFFFFF);
+  ctx.stencilOp(ctx.KEEP, ctx.KEEP, ctx.KEEP);
+  ctx.viewport(0, 0, ctx.canvas.clientWidth, ctx.canvas.clientHeight);
+  ctx.clear(ctx.COLOR_BUFFER_BIT | ctx.DEPTH_BUFFER_BIT | ctx.STENCIL_BUFFER_BIT);
+
+  // TODO: This should NOT be needed but Firefox fails with 'hint'
+  while(ctx.getError());
+}
+
+function makeLostContextSimulatingContext(ctx) {
+  var wrapper_ = {};
+  var contextId_ = 1;
+  var contextLost_ = false;
+  var resourceId_ = 0;
+  var resourceDb_ = [];
+  var onLost_ = undefined;
+  var onRestored_ = undefined;
+  var nextOnRestored_ = undefined;
+
+  // Holds booleans for each GL error so can simulate errors.
+  var glErrorShadow_ = { };
+
+  function isWebGLObject(obj) {
+    //return false;
+    return (obj instanceof WebGLBuffer ||
+            obj instanceof WebGLFramebuffer ||
+            obj instanceof WebGLProgram ||
+            obj instanceof WebGLRenderbuffer ||
+            obj instanceof WebGLShader ||
+            obj instanceof WebGLTexture);
+  }
+
+  function checkResources(args) {
+    for (var ii = 0; ii < args.length; ++ii) {
+      var arg = args[ii];
+      if (isWebGLObject(arg)) {
+        return arg.__webglDebugContextLostId__ == contextId_;
+      }
+    }
+    return true;
+  }
+
+  function clearErrors() {
+    var k = Object.keys(glErrorShadow_);
+    for (var ii = 0; ii < k.length; ++ii) {
+      delete glErrorShdow_[k];
+    }
+  }
+
+  // Makes a function that simulates WebglInstance when out of context.
+  function makeLostContextWrapper(ctx, functionName) {
+    var f = ctx[functionName];
+    return function() {
+      // Only call the functions if the context is not lost.
+      if (!contextLost_) {
+        if (!checkResources(arguments)) {
+          glErrorShadow_[ctx.INVALID_OPERATION] = true;
+          return;
+        }
+        var result = f.apply(ctx, arguments);
+        return result;
+      }
+    };
+  }
+
+  for (var propertyName in ctx) {
+    if (typeof ctx[propertyName] == 'function') {
+       wrapper_[propertyName] = makeLostContextWrapper(ctx, propertyName);
+     } else {
+       wrapper_[propertyName] = ctx[propertyName];
+     }
+  }
+
+  function makeWebGLContextEvent(statusMessage) {
+    return {statusMessage: statusMessage};
+  }
+
+  function freeResources() {
+    for (var ii = 0; ii < resourceDb_.length; ++ii) {
+      var resource = resourceDb_[ii];
+      if (resource instanceof WebGLBuffer) {
+        ctx.deleteBuffer(resource);
+      } else if (resource instanceof WebctxFramebuffer) {
+        ctx.deleteFramebuffer(resource);
+      } else if (resource instanceof WebctxProgram) {
+        ctx.deleteProgram(resource);
+      } else if (resource instanceof WebctxRenderbuffer) {
+        ctx.deleteRenderbuffer(resource);
+      } else if (resource instanceof WebctxShader) {
+        ctx.deleteShader(resource);
+      } else if (resource instanceof WebctxTexture) {
+        ctx.deleteTexture(resource);
+      }
+    }
+  }
+
+  wrapper_.loseContext = function() {
+    if (!contextLost_) {
+      contextLost_ = true;
+      ++contextId_;
+      while (ctx.getError());
+      clearErrors();
+      glErrorShadow_[ctx.CONTEXT_LOST_WEBGL] = true;
+      setTimeout(function() {
+          if (onLost_) {
+            onLost_(makeWebGLContextEvent("context lost"));
+          }
+        }, 0);
+    }
+  };
+
+  wrapper_.restoreContext = function() {
+    if (contextLost_) {
+      if (onRestored_) {
+        setTimeout(function() {
+            freeResources();
+            resetToInitialState(ctx);
+            contextLost_ = false;
+            if (onRestored_) {
+              var callback = onRestored_;
+              onRestored_ = nextOnRestored_;
+              nextOnRestored_ = undefined;
+              callback(makeWebGLContextEvent("context restored"));
+            }
+          }, 0);
+      } else {
+        throw "You can not restore the context without a listener"
+      }
+    }
+  };
+
+  // Wrap a few functions specially.
+  wrapper_.getError = function() {
+    if (!contextLost_) {
+      var err;
+      while (err = ctx.getError()) {
+        glErrorShadow_[err] = true;
+      }
+    }
+    for (var err in glErrorShadow_) {
+      if (glErrorShadow_[err]) {
+        delete glErrorShadow_[err];
+        return err;
+      }
+    }
+    return ctx.NO_ERROR;
+  };
+
+  var creationFunctions = [
+    "createBuffer",
+    "createFramebuffer",
+    "createProgram",
+    "createRenderbuffer",
+    "createShader",
+    "createTexture"
+  ];
+  for (var ii = 0; ii < creationFunctions.length; ++ii) {
+    var functionName = creationFunctions[ii];
+    wrapper_[functionName] = function(f) {
+      return function() {
+        if (contextLost_) {
+          return null;
+        }
+        var obj = f.apply(ctx, arguments);
+        obj.__webglDebugContextLostId__ = contextId_;
+        resourceDb_.push(obj);
+        return obj;
+      };
+    }(ctx[functionName]);
+  }
+
+  var functionsThatShouldReturnNull = [
+    "getActiveAttrib",
+    "getActiveUniform",
+    "getBufferParameter",
+    "getContextAttributes",
+    "getAttachedShaders",
+    "getFramebufferAttachmentParameter",
+    "getParameter",
+    "getProgramParameter",
+    "getProgramInfoLog",
+    "getRenderbufferParameter",
+    "getShaderParameter",
+    "getShaderInfoLog",
+    "getShaderSource",
+    "getTexParameter",
+    "getUniform",
+    "getUniformLocation",
+    "getVertexAttrib"
+  ];
+  for (var ii = 0; ii < functionsThatShouldReturnNull.length; ++ii) {
+    var functionName = functionsThatShouldReturnNull[ii];
+    wrapper_[functionName] = function(f) {
+      return function() {
+        if (contextLost_) {
+          return null;
+        }
+        return f.apply(ctx, arguments);
+      }
+    }(wrapper_[functionName]);
+  }
+
+  var isFunctions = [
+    "isBuffer",
+    "isEnabled",
+    "isFramebuffer",
+    "isProgram",
+    "isRenderbuffer",
+    "isShader",
+    "isTexture"
+  ];
+  for (var ii = 0; ii < isFunctions.length; ++ii) {
+    var functionName = isFunctions[ii];
+    wrapper_[functionName] = function(f) {
+      return function() {
+        if (contextLost_) {
+          return false;
+        }
+        return f.apply(ctx, arguments);
+      }
+    }(wrapper_[functionName]);
+  }
+
+  wrapper_.checkFramebufferStatus = function(f) {
+    return function() {
+      if (contextLost_) {
+        return ctx.FRAMEBUFFER_UNSUPPORTED;
+      }
+      return f.apply(ctx, arguments);
+    };
+  }(wrapper_.checkFramebufferStatus);
+
+  wrapper_.getAttribLocation = function(f) {
+    return function() {
+      if (contextLost_) {
+        return -1;
+      }
+      return f.apply(ctx, arguments);
+    };
+  }(wrapper_.getAttribLocation);
+
+  wrapper_.getVertexAttribOffset = function(f) {
+    return function() {
+      if (contextLost_) {
+        return 0;
+      }
+      return f.apply(ctx, arguments);
+    };
+  }(wrapper_.getVertexAttribOffset);
+
+  wrapper_.isContextLost = function() {
+    return contextLost_;
+  };
+
+  function wrapEvent(listener) {
+    if (typeof(listener) == "function") {
+      return listener;
+    } else {
+      return function(info) {
+        listener.handleEvent(info);
+      }
+    }
+  }
+
+  wrapper_.registerOnContextLostListener = function(listener) {
+    onLost_ = wrapEvent(listener);
+  };
+
+  wrapper_.registerOnContextRestoredListener = function(listener) {
+    if (contextLost_) {
+      nextOnRestored_ = wrapEvent(listener);
+    } else {
+      onRestored_ = wrapEvent(listener);
+    }
+  }
+
+  return wrapper_;
+}
+
+return {
+  /**
+   * Initializes this module. Safe to call more than once.
+   * @param {!WebGLRenderingContext} ctx A WebglInstance context. If
+   *    you have more than one context it doesn't matter which one
+   *    you pass in, it is only used to pull out constants.
+   */
+  'init': init,
+
+  /**
+   * Returns true or false if value matches any WebglInstance enum
+   * @param {*} value Value to check if it might be an enum.
+   * @return {boolean} True if value matches one of the WebglInstance defined enums
+   */
+  'mightBeEnum': mightBeEnum,
+
+  /**
+   * Gets an string version of an WebglInstance enum.
+   *
+   * Example:
+   *   WebGLDebugUtil.init(ctx);
+   *   var str = WebGLDebugUtil.glEnumToString(ctx.getError());
+   *
+   * @param {number} value Value to return an enum for
+   * @return {string} The string version of the enum.
+   */
+  'glEnumToString': glEnumToString,
+
+  /**
+   * Converts the argument of a WebglInstance function to a string.
+   * Attempts to convert enum arguments to strings.
+   *
+   * Example:
+   *   WebGLDebugUtil.init(ctx);
+   *   var str = WebGLDebugUtil.glFunctionArgToString('bindTexture', 0, gl.TEXTURE_2D);
+   *
+   * would return 'TEXTURE_2D'
+   *
+   * @param {string} functionName the name of the WebglInstance function.
+   * @param {number} argumentIndx the index of the argument.
+   * @param {*} value The value of the argument.
+   * @return {string} The value as a string.
+   */
+  'glFunctionArgToString': glFunctionArgToString,
+
+  /**
+   * Given a WebglInstance context returns a wrapped context that calls
+   * gl.getError after every command and calls a function if the
+   * result is not NO_ERROR.
+   *
+   * You can supply your own function if you want. For example, if you'd like
+   * an exception thrown on any GL error you could do this
+   *
+   *    function throwOnGLError(err, funcName, args) {
+   *      throw WebGLDebugUtils.glEnumToString(err) + " was caused by call to" +
+   *            funcName;
+   *    };
+   *
+   *    ctx = WebGLDebugUtils.makeDebugContext(
+   *        canvas.getContext("webgl"), throwOnGLError);
+   *
+   * @param {!WebGLRenderingContext} ctx The webgl context to wrap.
+   * @param {!function(err, funcName, args): void} opt_onErrorFunc The function
+   *     to call when gl.getError returns an error. If not specified the default
+   *     function calls console.log with a message.
+   */
+  'makeDebugContext': makeDebugContext,
+
+  /**
+   * Given a WebglInstance context returns a wrapped context that adds 4
+   * functions.
+   *
+   * ctx.loseContext:
+   *   simulates a lost context event.
+   *
+   * ctx.restoreContext:
+   *   simulates the context being restored.
+   *
+   * ctx.registerOnContextLostListener(listener):
+   *   lets you register a listener for context lost. Use instead
+   *   of addEventListener('webglcontextlostevent', listener);
+   *
+   * ctx.registerOnContextRestoredListener(listener):
+   *   lets you register a listener for context restored. Use
+   *   instead of addEventListener('webglcontextrestored',
+   *   listener);
+   *
+   * @param {!WebGLRenderingContext} ctx The webgl context to wrap.
+   */
+  'makeLostContextSimulatingContext': makeLostContextSimulatingContext,
+
+  /**
+   * Resets a context to the initial state.
+   * @param {!WebGLRenderingContext} ctx The webgl context to
+   *     reset.
+   */
+  'resetToInitialState': resetToInitialState
+};
+
+}();
+

lab2/lib/webgl-utils.js

+/*
+ * Copyright 2010, Google 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:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "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 THE COPYRIGHT
+ * OWNER 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.
+ */
+
+
+/**
+ * @fileoverview This file contains functions every webgl program will need
+ * a version of one way or another.
+ *
+ * Instead of setting up a context manually it is recommended to
+ * use. This will check for success or failure. On failure it
+ * will attempt to present an approriate message to the user.
+ *
+ *       gl = WebGLUtils.setupWebGL(canvas);
+ *
+ * For animated WebglInstance apps use of setTimeout or setInterval are
+ * discouraged. It is recommended you structure your rendering
+ * loop like this.
+ *
+ *       function render() {
+ *         window.requestAnimationFrame(render, canvas);
+ *
+ *         // do rendering
+ *         ...
+ *       }
+ *       render();
+ *
+ * This will call your rendering function up to the refresh rate
+ * of your display but will stop rendering if your app is not
+ * visible.
+ */
+
+WebGLUtils = function() {
+
+/**
+ * Creates the HTLM for a failure message
+ * @param {string} canvasContainerId id of container of th
+ *        canvas.
+ * @return {string} The html.
+ */
+var makeFailHTML = function(msg) {
+  return '' +
+        '<div style="margin: auto; width:500px;z-index:10000;margin-top:20em;text-align:center;">' + msg + '</div>';
+  return '' +
+    '<table style="background-color: #8CE; width: 100%; height: 100%;"><tr>' +
+    '<td align="center">' +
+    '<div style="display: table-cell; vertical-align: middle;">' +
+    '<div style="">' + msg + '</div>' +
+    '</div>' +
+    '</td></tr></table>';
+};
+
+/**
+ * Mesasge for getting a webgl browser
+ * @type {string}
+ */
+var GET_A_WEBGL_BROWSER = '' +
+  'This page requires a browser that supports WebglInstance.<br/>' +
+  '<a href="http://get.webgl.org">Click here to upgrade your browser.</a>';
+
+/**
+ * Mesasge for need better hardware
+ * @type {string}
+ */
+var OTHER_PROBLEM = '' +
+  "It doesn't appear your computer can support WebglInstance.<br/>" +
+  '<a href="http://get.webgl.org">Click here for more information.</a>';
+
+/**
+ * Creates a webgl context. If creation fails it will
+ * change the contents of the container of the <canvas>
+ * tag to an error message with the correct links for WebglInstance.
+ * @param {Element} canvas. The canvas element to create a
+ *     context from.
+ * @param {WebGLContextCreationAttirbutes} opt_attribs Any
+ *     creation attributes you want to pass in.
+ * @param {function:(msg)} opt_onError An function to call
+ *     if there is an error during creation.
+ * @return {WebGLRenderingContext} The created context.
+ */
+var setupWebGL = function(canvas, opt_attribs, opt_onError) {
+  function handleCreationError(msg) {
+      var container = document.getElementsByTagName("body")[0];
+    //var container = canvas.parentNode;
+    if (container) {
+      var str = window.WebGLRenderingContext ?
+           OTHER_PROBLEM :
+           GET_A_WEBGL_BROWSER;
+      if (msg) {
+        str += "<br/><br/>Status: " + msg;
+      }
+      container.innerHTML = makeFailHTML(str);
+    }
+  };
+
+  opt_onError = opt_onError || handleCreationError;
+
+  if (canvas.addEventListener) {
+    canvas.addEventListener("webglcontextcreationerror", function(event) {
+          opt_onError(event.statusMessage);
+        }, false);
+  }
+  var context = create3DContext(canvas, opt_attribs);
+  if (!context) {
+    if (!window.WebGLRenderingContext) {
+      opt_onError("");
+    } else {
+      opt_onError("");
+    }
+  }
+
+  return context;
+};
+
+/**
+ * Creates a webgl context.
+ * @param {!Canvas} canvas The canvas tag to get context
+ *     from. If one is not passed in one will be created.
+ * @return {!WebGLContext} The created context.
+ */
+var create3DContext = function(canvas, opt_attribs) {
+  var names = ["webgl", "experimental-webgl", "webkit-3d", "moz-webgl"];
+  var context = null;
+  for (var ii = 0; ii < names.length; ++ii) {
+    try {
+      context = canvas.getContext(names[ii], opt_attribs);
+    } catch(e) {}
+    if (context) {
+      break;
+    }
+  }
+  return context;
+}
+
+return {
+  create3DContext: create3DContext,
+  setupWebGL: setupWebGL
+};
+}();
+
+/**
+ * Provides requestAnimationFrame in a cross browser
+ * way.
+ */
+if (!window.requestAnimationFrame) {
+  window.requestAnimationFrame = (function() {
+    return window.requestAnimationFrame ||
+           window.webkitRequestAnimationFrame ||
+           window.mozRequestAnimationFrame ||
+           window.oRequestAnimationFrame ||
+           window.msRequestAnimationFrame ||
+           function(/* function FrameRequestCallback */ callback, /* DOMElement Element */ element) {
+             window.setTimeout(callback, 1000/60);
+           };
+  })();
+}
+
+/** * ERRATA: 'cancelRequestAnimationFrame' renamed to 'cancelAnimationFrame' to reflect an update to the W3C Animation-Timing Spec. 
+ * 
+ * Cancels an animation frame request. 
+ * Checks for cross-browser support, falls back to clearTimeout. 
+ * @param {number}  Animation frame request. */
+if (!window.cancelAnimationFrame) {
+  window.cancelAnimationFrame = (window.cancelRequestAnimationFrame ||
+                                 window.webkitCancelAnimationFrame || window.webkitCancelRequestAnimationFrame ||
+                                 window.mozCancelAnimationFrame || window.mozCancelRequestAnimationFrame ||
+                                 window.msCancelAnimationFrame || window.msCancelRequestAnimationFrame ||
+                                 window.oCancelAnimationFrame || window.oCancelRequestAnimationFrame ||
+                                 window.clearTimeout);
+}
\ No newline at end of file

lab2/src/lab2.html

+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>Simple model</title>
+</head>
+<body onload="main()">
+<canvas width="400" height="600" id="my-canvas">
+  Please use a browser that supports "canvas"
+</canvas>
+<script src="../lib/cuon-matrix.js"></script>
+<script src="../lib/webgl-utils.js"></script>
+<script src="../lib/webgl-debug.js"></script>
+<script src="../lib/cuon-utils.js"></script>
+<script src="lab2.js"></script>
+</body>
+</html>
\ No newline at end of file

lab2/src/lab2.js

+// Vertex shader program
+const VSHADER_SOURCE =
+  'attribute vec4 a_Position;\n' +
+  'attribute vec4 a_Color;\n' + // Attribute variable color to bind the effective vertex color from the model data
+  'uniform mat4 u_ModelViewMatrix;\n' +
+  'uniform mat4 u_ModelMatrixRotate;\n' +
+
+  'varying vec4 v_Color;\n' +   // Varying variable color to pass the vertex color to the fragment shader
+
+  'void main() {\n' +
+  '  gl_Position = u_ModelViewMatrix * u_ModelMatrixRotate * a_Position;\n' +
+
+  '  v_Color = a_Color;\n' +    // Set the varying color value with the attribute color value
+  '}\n';
+
+// Fragment shader program
+const FSHADER_SOURCE =
+  'precision mediump float;\n' + // This determines how much precision the GPU uses when calculating floats
+  'varying vec4 v_Color;\n' +   // Varying variable color to get the vertex color from
+                                // The vertex shader (!!same name as in the vertex shafer)
+  'void main() {\n' +
+  '  gl_FragColor = v_Color;\n' + // Set the fragment color with the vertex shader
+  '}\n';
+
+var ANGLE_STEP = 45.0;
+var currentAngle = 0.0;
+
+function main() {
+  // Retrieve <canvas> element
+  const canvas = document.getElementById('my-canvas');
+
+  // Get the rendering context for WebGL
+  const gl = getWebGLContext(canvas);
+  if (!gl) {
+    console.log('Failed to get the rendering context for WebGL');
+    return;
+  }
+
+  // Initialize shaders
+  if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
+    console.log('Failed to intialize shaders.');
+    return;
+  }
+
+  // Write the positions of vertices to a vertex shader
+  const n = initVertexBuffers(gl);
+  if (n < 0) {
+    console.log('Failed to set the positions of the vertices');
+    return;
+  }
+
+  // Specify the color for clearing <canvas>
+  gl.clearColor(0, 0, 0, 1);
+
+  
+  // Get the storage location of u_ModelViewMatrix
+  var u_ModelViewMatrix = gl.getUniformLocation(gl.program, 'u_ModelViewMatrix');
+  if(!u_ModelViewMatrix) { 
+    console.log('Failed to get the storage locations of u_ModelViewMatrix');
+    return;
+  }
+  
+  // Get the storage location of u_ModelMatrixRotate
+  var u_ModelMatrixRotate = gl.getUniformLocation(gl.program, 'u_ModelMatrixRotate');
+  if(!u_ModelMatrixRotate) { 
+    console.log('Failed to get the storage locations of u_ModelMatrixRotate');
+    return;
+  }
+  
+  // Set the matrix to be used for to set the camera view
+  var viewMatrix = new Matrix4();
+  viewMatrix.setLookAt(0.0, 0.0, 1, 0, 0, 0, 0, 1, 0);
+  
+  // Model matrix
+  var modelMatrixRotate = new Matrix4();
+  
+   // Start drawing
+  var tick = function() {
+    currentAngle = animate(currentAngle);  // Update the rotation angle
+    draw(gl, n, currentAngle, modelMatrixRotate, u_ModelMatrixRotate, viewMatrix, u_ModelViewMatrix);   // Draw the triangle
+    requestAnimationFrame(tick, canvas); // Request that the browser calls tick
+  };
+  tick();
+  
+  
+  
+  
+}
+
+function initVertexBuffers(gl) {
+  // This is the model
+  const vertices = new Float32Array([
+    // x     y   z
+	
+	-3/5,  3/7,	 0.5, 1.0, 0.0, 0.0,
+    3/5,  3/7,  0.5, 1.0, 0.0, 0.0,
+    0.0,  0.0, 0.0,  1.0,  0.0, 0.0, 
+	
+	3/5,  3/7,  0.5, 0.0, 1.0, 0.0,
+    3/5,  3/7,  -0.5, 0.0, 1.0, 0.0,
+    0.0,  0.0, 0.0,  0.0,  1.0, 0.0, 
+	
+	-3/5,  3/7,	 0.5, 1.0, 0.0, 1.0,
+	-3/5,  3/7,	 -0.5, 1.0, 0.0, 1.0,
+	0.0,  0.0, 0.0,  1.0,  0.0, 1.0,
+	
+	-3/5,  3/7,	 -0.5, 0.0, 0.0, 1.0,
+    3/5,  3/7,  -0.5, 0.0, 0.0, 1.0,
+    0.0,  0.0, 0.0,  0.0,  0.0, 1.0
+	
+  ]);
+  const n = vertices.length / 6; // The number of vertices
+  // Create a buffer object
+  const vertexBuffer = gl.createBuffer();
+  if (!vertexBuffer) {
+    console.log('Failed to create the buffer object');
+    return -1;
+  }
+
+  // Bind the buffer object to target
+  gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
+  // Write date into the buffer object
+  gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
+
+  // Get the storage location of a_Position, assign buffer and enable
+  const a_Position = gl.getAttribLocation(gl.program, 'a_Position');
+  if (a_Position < 0) {
+    console.log('Failed to get the storage location of a_Position');
+    return -1;
+  }
+  // Assign the buffer object to a_Position variable
+  // Read 2 elements of type gl.FLOAT, starting at the offset 0.
+  // Next offset will be 20: after 5 elements (x, y, r, g, and b) of 4 bytes (32 bits) each
+  gl.vertexAttribPointer(a_Position, 3, gl.FLOAT, false, 24, 0);
+  // Enable the assignment to a_Position variable
+  gl.enableVertexAttribArray(a_Position);
+
+  // Get the storage location of a_Color, assign buffer and enable
+  var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
+  if(a_Color < 0) {
+    console.log('Failed to get the storage location of a_Color');
+    return -1;
+  }
+  // Assign the buffer object to a_Color variable
+  // Read 3 elements of type gl.FLOAT, starting at the offset 8 (after 2 elements (x and z) of 4 bytes each).
+  // Next offset will be 20: after 5 elements (x, y, r, g, and b) of 4 bytes (32 bits) each
+  gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, 24, 12);
+  // Enable the assignment to a_Color variable
+  gl.enableVertexAttribArray(a_Color);
+
+  // Unbind the buffer object
+  gl.bindBuffer(gl.ARRAY_BUFFER, null);
+
+  return n;
+}
+
+function draw(gl, n, currentAngle, modelMatrixRotate, u_ModelMatrixRotate, viewMatrix, u_ModelViewMatrix) {
+  viewMatrix.rotate(0.5, 0, 1, 0);
+  //console.log(currentAngle);
+  // Multiply model matrix to view matrix
+  
+  // Set the view matrix
+  gl.uniformMatrix4fv(u_ModelViewMatrix, false, viewMatrix.elements);
+  // Set the rotation matrix
+  modelMatrixRotate.setRotate(0, 1, 0, 1); // Rotation angle, rotation axis (0, 0, 1)
+  var modelViewMatrix = viewMatrix.multiply(modelMatrixRotate);
+   gl.uniformMatrix4fv(u_ModelViewMatrix, false, modelViewMatrix.elements);
+  // Pass the rotation matrix to the vertex shader
+  gl.uniformMatrix4fv(u_ModelMatrixRotate, false, modelMatrixRotate.elements);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+
+  gl.drawArrays(gl.TRIANGLES, 0, n);
+  
+    // Set the rotation matrix
+  modelMatrixRotate.setRotate(180, 1, 0, 1); // Rotation angle, rotation axis (0, 0, 1)
+  //modelViewMatrix = viewMatrix.multiply(modelMatrixRotate);
+  gl.uniformMatrix4fv(u_ModelMatrixRotate, false, modelMatrixRotate.elements);
+  //gl.uniformMatrix4fv(u_ModelViewMatrix, false, modelViewMatrix.elements);
+
+  gl.drawArrays(gl.TRIANGLES, 0, n);
+}
+
+// Last time that this function was called
+var g_last = Date.now();
+function animate(angle) {
+  // Calculate the elapsed time
+  var now = Date.now();
+  var elapsed = now - g_last;
+  g_last = now;
+  // Update the current rotation angle (adjusted by the elapsed time)
+  var newAngle = angle + (ANGLE_STEP * elapsed) / 1000.0;
+  return newAngle %= 360;
+}