appendix/LoadShaderFromFiles

This is an example from the book "WebGL Programming Guide" by Kouichi Matsuda and Rodger Lea

by Ivan Enzhaev

HTML

<canvas id="webgl" width="400" height="400">
        Please use a browser that supports "canvas"
    </canvas>

    <script src="https://dl.dropboxusercontent.com/s/ylw7v7a44xtrwv0/webgl-utils.js"></script>
    <script src="https://dl.dropboxusercontent.com/s/iz1n21c8xafd76n/webgl-debug.js"></script>
    <script src="https://dl.dropboxusercontent.com/s/subm1yzylxuao8v/cuon-utils.js"></script>
    <script src="https://dl.dropboxusercontent.com/s/jw3p82lq1cjwekg/cuon-matrix.js"></script>

JavaScript

// LoadShaderFromFiles.js based on ColoredTriangle.js (c) 2012 matsuda
// This is an example from the book "WebGL Programming Guide"
// by Kouichi Matsuda and Rodger Lea

// Vertex shader program
var VSHADER_SOURCE = null;
// Fragment shader program
var FSHADER_SOURCE = null;

main();
//window.onload = main;

function main()
{
    // Retrieve <canvas> element
    var canvas = document.getElementById('webgl');

    // Get the rendering context for WebGL
    var gl = getWebGLContext(canvas);
    if (!gl)
    {
        console.log('Failed to get the rendering context for WebGL');
        return;
    }
    // Read shader from file
    //readShaderFile(gl, './ColoredTriangle.vert', 'v');
    //readShaderFile(gl, './ColoredTriangle.frag', 'f');
    // Read shader from file
    readShaderFile(gl, 'https://dl.dropboxusercontent.com/s/p9yihxes14zx6gk/ColoredTriangle.vert', 'v');
    readShaderFile(gl, 'https://dl.dropboxusercontent.com/s/xdd99o3xo69g6vu/ColoredTriangle.frag', 'f');
}

function start(gl)
{
    // Initialize shaders
    if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE))
    {
        console.log('Failed to intialize shaders.');
        return;
    }

    // Set vertex information
    var n = initVertexBuffers(gl);
    if (n < 0)
    {
        console.log('Failed to set the vertex information');
        return;
    }

    // Specify the color for clearing <canvas>
    gl.clearColor(0.0, 0.0, 0.0, 1.0);

    // Clear <canvas>
    gl.clear(gl.COLOR_BUFFER_BIT);

    // Draw the rectangle
    gl.drawArrays(gl.TRIANGLES, 0, n);
}

function initVertexBuffers(gl)
{
    var verticesColors = new Float32Array([
      // Vertex coordinates and color
       0.0, 0.5, 1.0, 0.0, 0.0,
      -0.5, -0.5, 0.0, 1.0, 0.0,
       0.5, -0.5, 0.0, 0.0, 1.0,
    ]);
    var n = 3;

    // Create a buffer object
    var vertexColorBuffer = gl.createBuffer();
    if (!vertexColorBuffer)
    {
        console.log('Failed to create the buffer object');
        return false;
    }

...