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palaviv
05-16-2011, 07:41 AM
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:


<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.vertexPos itionAttribute);

shaderProgram.textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");
gl.enableVertexAttribArray(shaderProgram.textureCo ordAttribute);

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.vertexPositio nAttribute, VertexPositionBuffer[i].itemSize, gl.FLOAT, false, 0, 0);

gl.bindBuffer(gl.ARRAY_BUFFER, VertexTextureCoordBuffer[i]);
gl.vertexAttribPointer(shaderProgram.textureCoordA ttribute, 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();">
&lt;&lt; Back to Lesson 5 (http://learningwebgl.com/blog/?p=507)


<canvas id="lesson05-canvas" style="border: none;" width="500" height="500"></canvas>



&lt;&lt; Back to Lesson 5 (http://learningwebgl.com/blog/?p=507)

</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