Hello,
i am new to webgl and i am trying to make an image slider. for now i just made the ring of image (nothing should slide yet) but it does not work and i dont know why.
i basically took the cood from this guide http://learningwebgl.com/blog/?p=507 and altered it:
Code :
<html>
 
<head>
<title>Learning WebGL &mdash; lesson 5</title>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
 
<script type="text/javascript" src="glMatrix-0.9.5.min.js"></script>
<script type="text/javascript" src="webgl-utils.js"></script>
 
<script id="shader-fs" type="x-shader/x-fragment">
    #ifdef GL_ES
    precision highp float;
    #endif
 
    varying vec2 vTextureCoord;
 
    uniform sampler2D uSampler;
 
    void main(void) {
        gl_FragColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
    }
</script>
 
<script id="shader-vs" type="x-shader/x-vertex">
    attribute vec3 aVertexPosition;
    attribute vec2 aTextureCoord;
 
    uniform mat4 uMVMatrix;
    uniform mat4 uPMatrix;
 
    varying vec2 vTextureCoord;
 
 
    void main(void) {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vTextureCoord = aTextureCoord;
    }
</script>
 
 
<script type="text/javascript">
 
    var gl;
	var	pics_num=5;
	var	pics_names=["a.jpg","b.jpg","c.jpg","d.jpg","e.jpg"]
 
 
    function initGL(canvas) {
        try {
            gl = canvas.getContext("experimental-webgl");
            gl.viewportWidth = canvas.width;
            gl.viewportHeight = canvas.height;
        } catch (e) {
        }
        if (!gl) {
            alert("Could not initialise WebGL, sorry :-(");
        }
    }
 
 
    function getShader(gl, id) {
        var shaderScript = document.getElementById(id);
        if (!shaderScript) {
            return null;
        }
 
        var str = "";
        var k = shaderScript.firstChild;
        while (k) {
            if (k.nodeType == 3) {
                str += k.textContent;
            }
            k = k.nextSibling;
        }
 
        var shader;
        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 {
            return null;
        }
 
        gl.shaderSource(shader, str);
        gl.compileShader(shader);
 
        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            alert(gl.getShaderInfoLog(shader));
            return null;
        }
 
        return shader;
    }
 
 
    var shaderProgram;
 
    function initShaders() {
        var fragmentShader = getShader(gl, "shader-fs");
        var vertexShader = getShader(gl, "shader-vs");
 
        shaderProgram = gl.createProgram();
        gl.attachShader(shaderProgram, vertexShader);
        gl.attachShader(shaderProgram, fragmentShader);
        gl.linkProgram(shaderProgram);
 
        if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
            alert("Could not initialise shaders");
        }
 
        gl.useProgram(shaderProgram);
 
        shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
        gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);
 
        shaderProgram.textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");
        gl.enableVertexAttribArray(shaderProgram.textureCoordAttribute);
 
        shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
        shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
        shaderProgram.samplerUniform = gl.getUniformLocation(shaderProgram, "uSampler");
    }
 
 
    function handleLoadedTexture(texture) {
        gl.bindTexture(gl.TEXTURE_2D, texture);
        gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, texture.image);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
        gl.bindTexture(gl.TEXTURE_2D, null);
    }
 
	function loadTexture(image) {
		var texture=gl.createTexture();
		texture.image=new Image()
		texture.image.onload = function () {
		        handleLoadedTexture(texture)
		}
		texture.image.src = image;
		return texture;
	}
 
 
    //var neheTexture;
	var Texture_array=new Array();	
 
    function initTexture() {
		for (var i=0;i<pics_num;i=i+1)
		{
		    //Texture_array[i] = gl.createTexture();
		    //Texture_array[i].image = new Image();
		    //Texture_array[i].image.onload = function () {
		    //    handleLoadedTexture(Texture_array[i])
		    //}
 
		    //Texture_array[i].image.src = pics_names[i];
			Texture_array[i]=loadTexture(pics_names[i]);
		}
    }
 
 
    var mvMatrix = mat4.create();
    var mvMatrixStack = [];
    var pMatrix = mat4.create();
 
    function mvPushMatrix() {
        var copy = mat4.create();
        mat4.set(mvMatrix, copy);
        mvMatrixStack.push(copy);
    }
 
    function mvPopMatrix() {
        if (mvMatrixStack.length == 0) {
            throw "Invalid popMatrix!";
        }
        mvMatrix = mvMatrixStack.pop();
    }
 
 
    function setMatrixUniforms() {
        gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
        gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
    }
 
 
    function degToRad(degrees) {
        return degrees * Math.PI / 180;
    }
 
    var VertexPositionBuffer=new Array();
    var VertexTextureCoordBuffer=new Array();
    var VertexIndexBuffer=new Array();
 
    function initBuffers() {
		for (var i=0;i<pics_num;i=i+1)
		{
		    VertexPositionBuffer[i] = gl.createBuffer();
		    gl.bindBuffer(gl.ARRAY_BUFFER, VertexPositionBuffer[i]);
		    vertices = [
		         Math.sin(i*((2*Math.PI)/pics_num)), -1.0,  Math.cos(i*((2*Math.PI)/pics_num)),
		          Math.sin(i*((2*Math.PI)/pics_num)), -1.0,  Math.cos(i*((2*Math.PI)/pics_num)),
		        Math.sin((i+1)*((2*Math.PI)/pics_num)), 1.0, Math.cos((i+1)*((2*Math.PI)/pics_num)),
		          Math.sin((i+1)*((2*Math.PI)/pics_num)), 1.0,  Math.cos((i+1)*((2*Math.PI)/pics_num)),
 
		    ];
		    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
		    VertexPositionBuffer[i].itemSize = 3;
		    VertexPositionBuffer[i].numItems = 4;
 
		    VertexTextureCoordBuffer[i] = gl.createBuffer();
		    gl.bindBuffer(gl.ARRAY_BUFFER,  VertexTextureCoordBuffer[i] );
		    var textureCoords = [
		      0.0, 0.0,
		      1.0, 0.0,
		      1.0, 1.0,
		      0.0, 1.0,
		    ];
		    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
		    VertexTextureCoordBuffer[i].itemSize = 2;
		    VertexTextureCoordBuffer[i].numItems = 4;
 
		    VertexIndexBuffer[i] = gl.createBuffer();
		    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, VertexIndexBuffer[i]);
		    var cubeVertexIndices = [
		        0, 1, 2,      0, 2, 3,  
		    ];
		    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
		    VertexIndexBuffer[i].itemSize = 1;
		    VertexIndexBuffer[i].numItems = 6;
		}
    }
 
 
 
    function drawScene() {
        gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
        gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
 
        mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);
 
        mat4.identity(mvMatrix);
 
        mat4.translate(mvMatrix, [0.0, 0.0, -5.0]);
 
		for (var i=0;i<pics_num;i=i+1)
		{
		    gl.bindBuffer(gl.ARRAY_BUFFER, VertexPositionBuffer[i]);
		    gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, VertexPositionBuffer[i].itemSize, gl.FLOAT, false, 0, 0);
 
		    gl.bindBuffer(gl.ARRAY_BUFFER, VertexTextureCoordBuffer[i]);
		    gl.vertexAttribPointer(shaderProgram.textureCoordAttribute, VertexTextureCoordBuffer[i].itemSize, gl.FLOAT, false, 0, 0);
 
		    gl.activeTexture(gl.TEXTURE0);
		    gl.bindTexture(gl.TEXTURE_2D, Texture_array[i]);
		    gl.uniform1i(shaderProgram.samplerUniform, 0);
 
		    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, VertexIndexBuffer[i]);
		    setMatrixUniforms();
		    gl.drawElements(gl.TRIANGLES, VertexIndexBuffer[i].numItems, gl.UNSIGNED_SHORT, 0);
		}
    }
 
 
 
 
 
 
    function webGLStart() {
        var canvas = document.getElementById("lesson05-canvas");
        initGL(canvas);
        initShaders();
        initBuffers();
        initTexture();
 
        gl.clearColor(0.0, 0.0, 0.0, 1.0);
        gl.enable(gl.DEPTH_TEST);
 
		drawScene();
    }
 
 
</script>
 
 
</head>
 
 
<body onload="webGLStart();">
    [url="http://learningwebgl.com/blog/?p=507"]&lt;&lt; Back to Lesson 5[/url]
 
 
    <canvas id="lesson05-canvas" style="border: none;" width="500" height="500"></canvas>
 
 
 
    [url="http://learningwebgl.com/blog/?p=507"]&lt;&lt; Back to Lesson 5[/url]
 
</body>
 
</html>

the final goal is to be able to make a ring of images that the user will be able to scroll left and write to see them all.

thanks for the help,
palaviv