eggheadio-projects/build-complex-3d-models-with-webgl: null

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
</head>
<body>
  <canvas id="canvas" width="600" height="600"></canvas>
  <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/gl-matrix/2.3.2/gl-matrix-min.js"></script>
  
  <script id="shader-vs" type="x-shader/x-vertex">
  attribute vec4 coords;
  uniform mat4 transformMatrix;
  attribute vec3 normal;
  uniform vec3 lightColor;
  uniform vec3 lightDirection;
  varying vec4 varyingColors;
  uniform mat4 perspectiveMatrix;
  void main(void) {
    vec3 norm = normalize(normal);
    vec3 ld = normalize(lightDirection);
    float dotProduct = max(dot(norm, ld), 0.0);
    vec3 vertexColor = lightColor * vec3(1, 1, 0) * dotProduct;
    varyingColors = vec4(vertexColor, 1);
    gl_Position = perspectiveMatrix * transformMatrix  * coords;
  }
  </script>
  
  <script id="shader-fs" type="x-shader/x-fragment">
  precision mediump float;
  varying vec4 varyingColors;
  void main(void) {
    gl_FragColor = varyingColors;
  }
  </script>
  <script src="lib/script.js"></script>
</body>
</html>

var gl,
    shaderProgram,
    vertices,
    matrix = mat4.create(),
    vertexCount,
    indexCount;


initGL();
createShaders();
createVertices();
createIndices();
draw();

function initGL() {
  var canvas = document.getElementById("canvas");
  gl = canvas.getContext("webgl");
  gl.enable(gl.DEPTH_TEST);
  gl.viewport(0, 0, canvas.width, canvas.height);
  gl.clearColor(0, 0, 0, 1);
}

function createShaders() {
  var vertexShader = getShader(gl, "shader-vs");
  var fragmentShader = getShader(gl, "shader-fs");
  
  shaderProgram = gl.createProgram();
  gl.attachShader(shaderProgram, vertexShader);
  gl.attachShader(shaderProgram, fragmentShader);
  gl.linkProgram(shaderProgram);
  gl.useProgram(shaderProgram);
}

function createVertices() {
  vertices = [
    -1, -1, -1,// 0
     1, -1, -1,// 1
    -1,  1, -1,// 2
     1,  1, -1,// 3
    -1,  1,  1,// 4
     1,  1,  1,// 5
    -1, -1,  1,// 6
     1, -1,  1,// 7
  ];

  vertexCount = vertices.length / 3;
  
  var buffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
  
  var coords = gl.getAttribLocation(shaderProgram, "coords");
  gl.vertexAttribPointer(coords, 3, gl.FLOAT, false, 0, 0);
  gl.enableVertexAttribArray(coords);  
  
  var normals = [
    0, 0, 1,   0, 0, 1,    0, 0, 1,   0, 0, 1,
    0, 1, 0,   0, 1, 0,    0, 1, 0,   0, 1, 0,
    0, 0, -1,  0, 0, -1,   0, 0, -1,  0, 0, -1,
    0, -1, 0,  0, -1, 0,   0, -1, 0,  0, -1, 0,
    -1, 0, 0,  -1, 0, 0,   -1, 0, 0,  -1, 0, 0,
    1, 0, 0,   1, 0, 0,    1, 0, 0,   1, 0, 0
  ];
  
  var normalBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, normalBuffer);
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(normals), gl.STATIC_DRAW);
  
  var normalLocation = gl.getAttribLocation(shaderProgram, "normal");
  gl.vertexAttribPointer(normalLocation, 3, gl.FLOAT, false, 0, 0);
  gl.enableVertexAttribArray(normalLocation);  
  gl.bindBuffer(gl.ARRAY_BUFFER, null);
  
  var lightColor = gl.getUniformLocation(shaderProgram, "lightColor");
  gl.uniform3f(lightColor, 1, 1, 1);
  
  var lightDirection = gl.getUniformLocation(shaderProgram, "lightDirection");
  gl.uniform3f(lightDirection, 0.5, 1, 0);
  
  var perspectiveMatrix = mat4.create();
  mat4.perspective(perspectiveMatrix, 1, canvas.width / canvas.height, 0.1, 11);
  var perspectiveLoc = gl.getUniformLocation(shaderProgram, "perspectiveMatrix");
  gl.uniformMatrix4fv(perspectiveLoc, false, perspectiveMatrix);
  
  mat4.translate(matrix, matrix, [0, 0, -4]);
}

function createIndices() {
  var indices = [
    0, 1, 2,   1, 2, 3,
    2, 3, 4,   3, 4, 5,
    4, 5, 6,   5, 6, 7,
    6, 7, 0,   7, 0, 1,
    0, 2, 6,   2, 6, 4,
    1, 3, 7,   3, 7, 5
  ];
  indexCount = indices.length;
  
  var indexBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
  gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint8Array(indices), gl.STATIC_DRAW);
}

function draw() {
  mat4.rotateX(matrix, matrix, -0.007);
  mat4.rotateY(matrix, matrix, 0.013);
  mat4.rotateZ(matrix, matrix, 0.01);

  var transformMatrix = gl.getUniformLocation(shaderProgram, "transformMatrix");
  gl.uniformMatrix4fv(transformMatrix, false, matrix);
  
  gl.clear(gl.COLOR_BUFFER_BIT);
//   gl.drawArrays(gl.TRIANGLE_STRIP, 0, vertexCount);
  gl.drawElements(gl.TRIANGLES, indexCount, gl.UNSIGNED_BYTE, 0);
  requestAnimationFrame(draw);
}


  /*
   * https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Tutorial/Adding_2D_content_to_a_WebGL_context
   */
  function getShader(gl, id) {
    var shaderScript, theSource, currentChild, shader;

    shaderScript = document.getElementById(id);

    if (!shaderScript) {
      return null;
    }

    theSource = "";
    currentChild = shaderScript.firstChild;

    while (currentChild) {
      if (currentChild.nodeType == currentChild.TEXT_NODE) {
        theSource += currentChild.textContent;
      }

      currentChild = currentChild.nextSibling;
    }
    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 {
      // Unknown shader type
      return null;
    }
    gl.shaderSource(shader, theSource);

// Compile the shader program
    gl.compileShader(shader);

// See if it compiled successfully
    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
      alert("An error occurred compiling the shaders: " + gl.getShaderInfoLog(shader));
      return null;
    }

    return shader;
  }