Quelltext der Seite Tutorial WebGL Sample

Dies ist eine Beispielanwendung zum [[Benutzer:Coolcat/Tutorial_WebGL|WebGL-Tutorial]]. Zum Ausprobieren den Quelltext in eine Datei kopieren und mit einem [[Benutzer:Coolcat/Tutorial_WebGL|WebGL-fähigen Browser]] öffnen. Es wird eine Textur von der URL <tt><nowiki>"http://wiki.delphigl.com/wiki.png"</nowiki></tt> geladen. Sollte die Anwendung nicht funktionieren, stelle sicher, dass die Textur erreichbar ist.

Das Ganze sollte ungefähr so aussehen:

[[Bild:webgl-sample.jpg|320px]]

<source lang="html4strict">
<html>
    <!--
     * WebGL-Test
     * 
     * This sample is part of the WebGL Tutorial at http://delphigl.com
     *
     * Author:
     * Coolcat (Martin Weusten)
     *   see: http://wiki.delphigl.com/index.php/Benutzer:Coolcat
     *
     * Licence for this file:
     * Creative Commons Attribution 3.0 (CC-BY 3.0)
     *   see: http://creativecommons.org/licenses/by/3.0/
    -->

    <head>
         <script type="text/javascript">
            var gl = null; // our WebGL rendering context
            var viewportWidth;
            var viewportHeight;
            
            var program; // shader program object
            var vbo;     // vertexbufferobject
            var texture; // texture object

            function init() { 
                // request rendering context from the canvas
                // =================================================
                var canvas = document.getElementById("canvas");
                viewportWidth = canvas.width;
                viewportHeight = canvas.height;
                try {
                    // using Mozilla? (e.g. Firefox, ...) 
                    if (!gl) { gl = canvas.getContext("moz-webgl"); } 
                } catch (e) { }
                try {
                    // using Webkit? (e.g. Google Chrome, ...)
                    if (!gl) { gl = canvas.getContext("webkit-3d"); } 
                } catch (e) { }
                 
                if (!gl) {
                    alert("No known OpenGL context detected! Is it enabled?");
                    return;
                }

                // basic settings
                // =================================================
                gl.clearColor(0, 0, 0, 1);
                gl.enable(gl.DEPTH_TEST);

                // setup shaders
                // =================================================
                var vertexShaderSource = getShaderSource("shader-vs");
                var fragmentShaderSource = getShaderSource("shader-fs");

                var vertexShader = loadShader(gl.VERTEX_SHADER, vertexShaderSource);
                var fragmentShader = loadShader(gl.FRAGMENT_SHADER, fragmentShaderSource);
                if (!vertexShader || !fragmentShader) {
                    alert("Shader problem");
                }
                 
                // create program object
                program = gl.createProgram();
                 
                // attach our two shaders to the program
                gl.attachShader(program, vertexShader);
                gl.attachShader(program, fragmentShader);
                 
                // setup attributes and uniforms (optional)
                gl.bindAttribLocation(program, 0, "aPosition");
                gl.bindAttribLocation(program, 1, "aNormal");
                gl.bindAttribLocation(program, 2, "aTexCoord");
                gl.uniform1i(gl.getUniformLocation(program, "uTexture"), 0);
                 
                // linking
                gl.linkProgram(program);
                if (!gl.getProgrami(program, gl.LINK_STATUS)) {
                    alert(gl.getProgramInfoLog(program));
                }

                // setup VBO
                // =================================================

                // define some vertexdata
                var vertices = [
                    // position XYZ, normal XYZ, texcoord UV => 8 floats per vertex
                    -0.5,  0.5,  0.0,  0.6,  0.0,  0.8,  0.0,  0.0,
                     0.5,  0.5,  0.0,  0.6,  0.0,  0.8,  1.0,  0.0,
                    -0.5, -0.5,  0.0,  0.0,  0.0,  1.0,  0.0,  1.0,
                     0.5, -0.5,  0.0,  0.0,  0.6,  0.8,  1.0,  1.0,
                 
                    // add an additional vertex, this is an workaround for this bug:
                    // https://bugzilla.mozilla.org/show_bug.cgi?id=521667
                     0.0,  0.0,  0.0,  0.0,  0.0,  0.0,  0.0,  0.0 
                ];                 
                // create VBO
                vbo = gl.createBuffer();
                gl.bindBuffer(gl.ARRAY_BUFFER, vbo);
                gl.bufferData(gl.ARRAY_BUFFER, new CanvasFloatArray(vertices), gl.STATIC_DRAW);
                 
                // create texture
                // =================================================
                texture = loadTexture("http://wiki.delphigl.com/wiki.png");
            }

            function getShaderSource(id) {
                var script = document.getElementById(id);
                if (!script) { return null; }
             
                var source = "";
                var child = script.firstChild;
                while (child) {
                    // node is a "textnode" ?
                    if (child.nodeType == 3) {
                        source += child.textContent;
                    }
                    child = child.nextSibling;
                }
                return source;
            }
 
            function loadShader(shaderType, shaderSource) {
                var shader = gl.createShader(shaderType);
                if (!shader) { return null; }    
                gl.shaderSource(shader, shaderSource);
                gl.compileShader(shader);
             
                if (!gl.getShaderi(shader, gl.COMPILE_STATUS)) {
                    alert(gl.getShaderInfoLog(shader));
                    return null;
                }    
             
                return shader;
            }

            function loadTexture(filename) {
                // preparations
                var texture = gl.createTexture();
                gl.bindTexture(gl.TEXTURE_2D, texture);
                gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
                gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
                var image = new Image();
             
                // register event handlers
                image.onload = function() {
                    gl.bindTexture(gl.TEXTURE_2D, texture);
                    gl.texImage2D(gl.TEXTURE_2D, 0, image);
                    gl.generateMipmap(gl.TEXTURE_2D);
                    draw(); // texture now available, we can redraw the scene
                }
                image.onerror = function() {
                    alert("error while loading image '"+filename+"'.");
                }
             
                // request image from server
                image.src = filename; 
             
                // return texture object (asynchronous loading, texture NOT available yet!)
                return texture;
            }

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

                // setup shader
                gl.useProgram(program);

                // setup interleaved VBO
                gl.bindBuffer(gl.ARRAY_BUFFER, vbo);                     
                gl.enableVertexAttribArray(0);
                gl.enableVertexAttribArray(1);
                gl.enableVertexAttribArray(2);
                gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 8, 0); // position
                gl.vertexAttribPointer(1, 3, gl.FLOAT, false, 8, 3); // normal
                gl.vertexAttribPointer(2, 2, gl.FLOAT, false, 8, 6); // texcoord

                // setup texture
                gl.activeTexture(gl.TEXTURE0);
                gl.bindTexture(gl.TEXTURE_2D, texture);
                 
                // draw the buffer
                gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
            }
        </script>

        <script id="shader-vs" type="x-shader/x-vertex">
            attribute vec3 aPosition;
            attribute vec3 aNormal;
            attribute vec3 aTexCoord;
            varying vec3 vNormal;
            varying vec2 vTexCoord; 
            void main() {
                gl_Position = vec4(aPosition, 1.0);
                vTexCoord = aTexCoord;
                vNormal = aNormal;
            }
        </script>
         
        <script id="shader-fs" type="x-shader/x-fragment">
            varying vec3 vNormal;
            varying vec2 vTexCoord;
            uniform sampler2D uTexture;
            void main() {
                gl_FragColor = texture2D(uTexture, vTexCoord);
            }
        </script>
    </head>
    <body onload="init()">
        <div style="text-align: center">
            <canvas id="canvas" width="512" height="512"></canvas>
        </div>
    </body>
</html>
</source>