1.  
2. main();
3.  
4. function main() {
5.   const canvas = document.querySelector('#glcanvas');
6.   const gl = canvas.getContext('webgl');
7.  
8.  
9.   if (!gl) {
10.     alert('Unable to initialize WebGL. Your browser or machine may not support it.');
11.     return;
12.   }
13.  
14.  
15.   const shaderProgramFactory = new ShaderProgramFactory(gl);
16.   const shaderProgram = shaderProgramFactory.createShaderProgram();
17.  
18.   // Collect all the info needed to use the shader program.
19.   // Look up which attributes our shader program is using
20.   // for aVertexPosition, aVertexNormal, aTextureCoord,
21.   // and look up uniform locations.
22.   const programInfo = {
23.     program: shaderProgram,
24.     attribLocations: {
25.       vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
26.       vertexNormal: gl.getAttribLocation(shaderProgram, 'aVertexNormal'),
27.       textureCoord: gl.getAttribLocation(shaderProgram, 'aTextureCoord'),
28.     },
29.     uniformLocations: {
30.       projectionMatrix: gl.getUniformLocation(shaderProgram, 'uProjectionMatrix'),
31.       modelViewMatrix: gl.getUniformLocation(shaderProgram, 'uModelViewMatrix'),
32.       normalMatrix: gl.getUniformLocation(shaderProgram, 'uNormalMatrix'),
33.       uSampler: gl.getUniformLocation(shaderProgram, 'uSampler'),
34.     },
35.   };
36.  
37.  
38.   const cubeBuffer = new CubeBuffer(gl);
39.   const buffers = cubeBuffer.startBuffer();
40.  
41.   const imageLoader = new ImageLoader(gl);
42.   const texture = imageLoader.loadImageIntoTexture( 'cubetexture.png');
43.  
44.   var then = 0;
45.  
46.   // Draw the scene repeatedly
47.   function render(now) {
48.     now *= 0.001;  // convert to seconds
49.     const deltaTime = now - then;
50.     then = now;
51.  
52.     drawScene(gl, programInfo, buffers, texture, deltaTime);
53.  
54.     requestAnimationFrame(render);
55.   }
56.   requestAnimationFrame(render);
57. }
58.  
59.  
60.