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Adding background image to WebGL 3D scene - javascript

I wrote a code that tried to draw only the background image in a WebGL 3D scene. Here are the relevant parts of the code:
<script id="shader-fs" type="x-shader/x-fragment">
varying highp vec2 vTexCoord;
uniform sampler2D uSampler;
void main(void) {
gl_FragColor = texture2D(uSampler, vec2(vTexCoord.s, vTexCoord.t));
}
</script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec3 aVertexPosition;
attribute vec2 aTextureCoord;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
varying highp vec2 vTexCoord;
void main(void) {
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
vTexCoord = aTextureCoord;
}
</script>
<script>
var VBack = [
-24.0, 0.0, 0.0,
24.0, 0.0, 0.0,
24.0, 48.0, 0.0,
-24.0, 48.0, 0.0
];
var vTBack = [
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0
];
var VBuffer;
var vTBuffer;
function initMatrix() {
orthoMatrix = makeOrtho(-24.0, 24.0, 0.0, 48.0, 20.0, -20.0); // From glUtils.js
mvMatrix = Matrix.I(4);
...
}
function handleBkTex(tex) {
GL.bindTexture(GL.TEXTURE_2D, tex);
GL.pixelStorei(GL.UNPACK_FLIP_Y_WEBGL, true);
GL.texImage2D(GL.TEXTURE_2D, 0, GL.RGBA, GL.RGBA, GL.UNSIGNED_BYTE, tex.Img);
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 initBkgnd() {
backTex = GL.createTexture();
backTex.Img = new Image();
backTex.Img.onload = function() {
handleBkTex(backTex);
}
backTex.Img.src = "Bkgnd.jpg";
}
function drawBkgnd() {
GL.bindBuffer(GL.ARRAY_BUFFER, VBuffer);
GL.vertexAttribPointer(vertexPositionAttribute, 3, GL.FLOAT, false, 0, 0);
GL.bindBuffer(GL.ARRAY_BUFFER, vTBuffer);
GL.vertexAttribPointer(texCoordAttribute, 2, GL.FLOAT, false, 0, 0);
GL.activeTexture(GL.TEXTURE0);
GL.bindTexture(GL.TEXTURE_2D, backTex);
GL.uniform1i(GL.getUniformLocation(shaderProgram, "uSampler"), 0);
GL.drawArrays(GL.TRIANGLE_STRIP, 0, 4);
}
function start() {
var canvas = document.getElementById("glcanvas");
initWebGL(canvas);
if (GL) {
initShaders();
initBuffers();
initMatrix();
initBkgnd();
drawBkgnd();
}
}
The canvas size is 512 x 512, the same as the image size. But I don't get the correct image on the canvas. How to do this correctly?

Do you want the answer to be how to setup a 3D matrix to draw a 2D image or do you want the answer to be how to do this efficiently?
Here's the efficient answer. There's no reason to use 3D to draw 2D. Change your vertices to
var VBack = [
-1, -1,
1, -1,
1, 1,
-1, 1,
];
Change your call to vertexAttribPointer to
GL.vertexAttribPointer(vertexPositionAttribute, 2, GL.FLOAT, false, 0, 0);
Change your vertex shader to
attribute vec4 aVertexPosition;
attribute vec2 aTextureCoord;
varying highp vec2 vTexCoord;
void main(void) {
gl_Position = aVertexPosition;
vTexCoord = aTextureCoord;
}
And it should work.
See this set of articles for more about 2D in WebGL for more.

I found some small errors in my code. Here are they:
WebGL scene must always be redrawn. So the function drawBkgnd() must be called repeatedly, using setInterval() or requestAnimationFrame().
To use drawArrays() with GL_TRIANGLE_STRIP to draw a rectangle correctly, the order of the vertices must be:
*2 *3
*0 *1
or any equivalent order, but not:
*3 *2
*0 *1
So the order of the vertices in VBack must be changed to:
var VBack = [
-24.0, 0.0, 0.0,
24.0, 0.0, 0.0,
-24.0, 48.0, 0.0
24.0, 48.0, 0.0,
];
and the order of vertices in vTBack must also be changed accordingly.

Related

I try to transform two 3D objects separately and I failed, it seems each translation is apply to both objects . They are translating together. And what really confusing is t1,which is scaling,it applys to only one object successfully , but its translation ,t2 affects itself and also the another object ,and so do the translation t1 .Any help is appreciated.
The important codes :
gl.bindVertexArray(vao2);
var t1 = mat4(2.0, 0.0, 0.0, 0.0,
0.0, 1.0, 0.0, 0.0,
0.0, 0.0, 2.0, 0.0,
0.0, 0.0, 0.0, 1.0);
var t2 = translate( 0.0, -0.5, 0.0 );
let changedmodelMatrix1 = mat4(1.0)
changedmodelMatrix1 =mult(t2,mult(t1,modelMatrix));
let changedMvpmodelMatrix1 = mult(mult(projectionMatrix, viewMatrix), changedmodelMatrix1);
gl.uniformMatrix4fv(
gl.getUniformLocation(program, "u_mvp1"),
gl.FALSE,
flatten(changedMvpmodelMatrix1));
gl.drawArrays(gl.TRIANGLES, 0, 18);
gl.bindVertexArray(vao1);
var t3 = translate(0.0, 0.3, 0.0);
let changedmodelMatrix2 = mat4(1.0);
changedmodelMatrix2 = mult(t3,modelMatrix);
let changedMvpmodelMatrix2 = mult(mult(projectionMatrix, viewMatrix), changedmodelMatrix2);
gl.uniformMatrix4fv(
gl.getUniformLocation(program, "u_mvp2"),
gl.FALSE,
flatten(changedMvpmodelMatrix2));
gl.drawArrays(gl.TRIANGLES, 0, vertexCounter);
html:
layout(location = 0) in vec3 a_position;
layout(location = 1) in vec4 a_teapotposition;
uniform mat4 u_mvp1;
uniform mat4 u_mvp2;
void main() {
gl_Position = u_mvp2 *
a_teapotposition
+
u_mvp1 *
vec4(a_position, 1.0)
;

You don't need 2 attributes and 2 matrix uniform variables.
Create a simple shader program:
layout(location = 0) in vec3 a_position;
uniform mat4 u_mvp;
void main()
{
gl_Position = u_mvp * a_position;
}
Bind the Vertex Array Object and set the uniform before drawing the object:
gl.bindVertexArray(vao2);
gl.uniformMatrix4fv(
gl.getUniformLocation(program, "u_mvp"),
gl.FALSE,
flatten(changedMvpmodelMatrix1));
gl.drawArrays(gl.TRIANGLES, 0, 18);
gl.bindVertexArray(vao1);
gl.uniformMatrix4fv(
gl.getUniformLocation(program, "u_mvp"),
gl.FALSE,
flatten(changedMvpmodelMatrix2));
gl.drawArrays(gl.TRIANGLES, 0, vertexCounter);

I've been trying to learn some webgl, and basically have two programs where the rendered pixels get stored in a texture and then used in the other program's shader.
webgl.modTexture(gl, webgl.texture[1], webgl.frameBuffer[0]);
This will call and attempt to readpixels of a screen and put the modified data back into the texture to be used in the next program render routine.
All I get is a black screen becoming more transparent gradually, but there should be the u_image being seen also (since this is being rendered in the first program where the pixels are read with readpixels).
If I comment out the second program's rendering:
gl.useProgram(webgl.program);
gl.clearColor(0, 0.5, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, 6);
Then it will just render u_image without any fading.
So I'm not sure what is the problem. Seems like maybe it isn't reading the pixels correctly? But then, why would the fading be working if that's the case? Is there something wrong with trying to use the two textures?
Hopefully someone can look at the code and see what might be the issue.
//webgl stuff
var webgl = new webglData();
function webglData(){
this.then = 0; //used for deltatime in rendering
this.request; //requestanimationframe, used when stopping/starting
this.canvas;
this.context;
this.div;
this.program;
this.cellProgram;
this.texture = [];
this.frameBuffer = [];
this.cellVShader = `
attribute vec2 aVertexPosition;
attribute vec2 a_position;
attribute vec2 a_texCoord;
uniform vec2 u_resolution;
varying vec2 v_texCoord;
varying vec2 v_NW;
varying vec2 v_N;
varying vec2 v_NE;
varying vec2 v_W;
varying vec2 v_E;
varying vec2 v_SW;
varying vec2 v_S;
varying vec2 v_SE;
vec2 getOffset( int x, int y){
vec2 v = floor(a_texCoord * u_resolution);
v.x += float(x), v.y += float(y);
v /= u_resolution;
return v;
}
void main() {
//v_texCoord = a_texCoord;
//gl_Position = vec4(aVertexPosition, 0.0, 1.0);
// convert the rectangle from pixels to 0.0 to 1.0
vec2 zeroToOne = a_position / u_resolution;
// convert from 0->1 to 0->2
vec2 zeroToTwo = zeroToOne * 2.0;
// convert from 0->2 to -1->+1 (clipspace)
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
// pass the texCoord to the fragment shader
// The GPU will interpolate this value between points.
v_texCoord = a_texCoord;
v_NW = getOffset( -1, 1);
v_N = getOffset( 0, 1);
v_NE = getOffset( 1, 1);
v_W = getOffset( -1, 0);
v_E = getOffset( 1, 0);
v_SW = getOffset( -1, -1);
v_S = getOffset( 0, -1);
v_SE = getOffset( 1, -1);
}
`;
this.cellFShader = `
#ifdef GL_ES
precision highp float;
#endif
uniform sampler2D u_canvas1;
uniform vec4 uColor;
// our texture
uniform sampler2D u_before;
uniform sampler2D u_after;
uniform sampler2D u_image;
// the texCoords passed in from the vertex shader.
varying vec2 v_texCoord;
varying vec2 v_NW;
varying vec2 v_N;
varying vec2 v_NE;
varying vec2 v_W;
varying vec2 v_E;
varying vec2 v_SW;
varying vec2 v_S;
varying vec2 v_SE;
void main() {
// Look up a color from the texture.
gl_FragColor = texture2D(u_image, v_W);
//gl_FragColor = uColor;
}
`;
this.vertexShader = `
attribute vec2 aVertexPosition;
attribute vec2 a_position;
attribute vec2 a_texCoord;
uniform vec2 u_resolution;
varying vec2 v_texCoord;
void main() {
//v_texCoord = a_texCoord;
//gl_Position = vec4(aVertexPosition, 0.0, 1.0);
// convert the rectangle from pixels to 0.0 to 1.0
vec2 zeroToOne = a_position / u_resolution;
// convert from 0->1 to 0->2
vec2 zeroToTwo = zeroToOne * 2.0;
// convert from 0->2 to -1->+1 (clipspace)
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
// pass the texCoord to the fragment shader
// The GPU will interpolate this value between points.
v_texCoord = a_texCoord;
}
`;
this.fragmentShader = `
#ifdef GL_ES
precision highp float;
#endif
uniform sampler2D u_canvas1;
uniform vec4 uColor;
// our texture
uniform sampler2D u_before;
uniform sampler2D u_after;
uniform sampler2D u_image;
// the texCoords passed in from the vertex shader.
varying vec2 v_texCoord;
void main() {
// Look up a color from the texture.
gl_FragColor = texture2D(u_before, v_texCoord);
//gl_FragColor = uColor;
}
`;
this.init = function(){
this.div = innerDoc.getElementById('webglDiv');
gui.Window.get().showDevTools();
this.canvas = document.createElement('canvas');
this.context = this.canvas.getContext("experimental-webgl");
this.canvas.width = 512;
this.canvas.height = 512;
this.canvas.style.position = 'absolute';
this.canvas.style.zIndex = -1;
this.canvas.style.pointerEvents = 'none';
this.div.appendChild(this.canvas);
if(!this.context)return;
var gl = this.context;
gl.viewport(0, 0, this.canvas.width, this.canvas.height);
gl.clearColor(0, 0.5, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
//compile the shaders and create the program for webgl
var vs = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(vs, this.vertexShader);
gl.compileShader(vs);
var fs = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(fs, this.fragmentShader);
gl.compileShader(fs);
var cvs = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(cvs, this.cellVShader);
gl.compileShader(cvs);
var cfs = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(cfs, this.cellFShader);
gl.compileShader(cfs);
this.program = gl.createProgram();
gl.attachShader(this.program, vs);
gl.attachShader(this.program, fs);
gl.linkProgram(this.program);
//gl.useProgram(this.program);
this.cellProgram = gl.createProgram();
gl.attachShader(this.cellProgram, cvs);
gl.attachShader(this.cellProgram, cfs);
gl.linkProgram(this.cellProgram);
//gl.useProgram(this.cellProgram);
//output any errors
if (!gl.getShaderParameter(vs, gl.COMPILE_STATUS))console.log(gl.getShaderInfoLog(vs));
if (!gl.getShaderParameter(fs, gl.COMPILE_STATUS))console.log(gl.getShaderInfoLog(fs));
if (!gl.getProgramParameter(this.program, gl.LINK_STATUS))console.log(gl.getProgramInfoLog(this.program));
if (!gl.getShaderParameter(cvs, gl.COMPILE_STATUS))console.log(gl.getShaderInfoLog(cvs));
if (!gl.getShaderParameter(cfs, gl.COMPILE_STATUS))console.log(gl.getShaderInfoLog(cfs));
if (!gl.getProgramParameter(this.cellProgram, gl.LINK_STATUS))console.log(gl.getProgramInfoLog(this.cellProgram));
this.setupStuff(gl, this.program);
this.setupStuff(gl, this.cellProgram);
this.texture.push( this.setupTexture(tool.canvas, 0, "u_image") );
this.texture.push( this.createBlankTexture(gl, tool.canvas.width*tool.canvas.height*4, gl.RGBA, tool.canvas.width, tool.canvas.height, "u_before") );
this.texture.push( this.createBlankTexture(gl, tool.canvas.width*tool.canvas.height*4, gl.RGBA, tool.canvas.width, tool.canvas.height, "u_after") );
this.frameBuffer.push( gl.createFramebuffer() );
this.request = requestAnimationFrame(this.render);
}
this.render = function(now){
if(!webgl.context || config.tab!='scene'){cancelAnimationFrame(webgl.request); return;}
var gl = webgl.context;
// Convert the time to seconds
now *= 0.001;
// Subtract the previous time from the current time
var deltaTime = now - webgl.then;
// Remember the current time for the next frame.
webgl.then = now;
gl.useProgram(webgl.cellProgram);
gl.drawArrays(gl.TRIANGLES, 0, 6);
webgl.modTexture(gl, webgl.texture[1], webgl.frameBuffer[0]);
gl.useProgram(webgl.program);
gl.clearColor(0, 0.5, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, 6);
this.request = requestAnimationFrame(webgl.render);
}
this.setupStuff = function(gl, program){
gl.useProgram(program);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
var texCoordLocation = gl.getAttribLocation(program, "a_texCoord");
// provide texture coordinates for the rectangle.
//this will be what the texture gets displayed on?
var texCoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, texCoordBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
0.0, 0.0,
1.0, 0.0,
0.0, 1.0,
0.0, 1.0,
1.0, 0.0,
1.0, 1.0]), gl.STATIC_DRAW);
gl.enableVertexAttribArray(texCoordLocation);
gl.vertexAttribPointer(texCoordLocation, 2, gl.FLOAT, false, 0, 0);
// lookup uniforms
var resolutionLocation = gl.getUniformLocation(program, "u_resolution");
// set the resolution
gl.uniform2f(resolutionLocation, this.canvas.width, this.canvas.height);
// Create a buffer for the position of the rectangle corners.
// store the data for the texture coordinates that were defined above, into the a_position?
var buffer = gl.createBuffer();
//this.frameBuffer.push(buffer);
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.enableVertexAttribArray(positionLocation);
gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);
// Set a rectangle the same size as the image.
//I guess this adjusts the buffer data that was just created?
this.setRectangle(gl, 0, 0, this.canvas.width, this.canvas.height);
//var tex2 = setupTexture(canvas2, 1, program, "u_canvas2");
// Draw the rectangle.
//gl.drawArrays(gl.TRIANGLES, 0, 6);
//gl.drawArrays(gl.TRIANGLES, 0, numItems);
}
this.refreshTexture = function(){
if(!this.context)return;
var gl = this.context;
gl.activeTexture(gl.TEXTURE0 + 0);
gl.bindTexture(gl.TEXTURE_2D, this.texture[0]);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, tool.canvas);
//gl.drawArrays(gl.TRIANGLES, 0, 6);
}
this.modTexture = function(gl, sTexture, framebuffer){
gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, sTexture, 0);
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE)
{
var sTextureSize = sTexture.width * sTexture.height * 4; // r, g, b, a
var pixels = new Uint8Array( sTextureSize );
gl.readPixels( 0, 0, sTexture.width, sTexture.height, gl.RGBA, gl.UNSIGNED_BYTE, pixels );
for( var i=0 ; i<sTextureSize ; i+=4 )
{
if( pixels[i+3] > 0 )
{
pixels[i+3] = Math.min( 255, pixels[i+3]*0.995 ); // set half alpha
}
}
// upload changes
gl.activeTexture(gl.TEXTURE0 + 1);
gl.bindTexture(gl.TEXTURE_2D, sTexture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA,
sTexture.width, sTexture.height, 0,
gl.RGBA, gl.UNSIGNED_BYTE, pixels);
}
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
}
this.setupFrameBuffer = function(canvas, textureUnit, program, uniformName) {
if(!this.context)return;
var gl = this.context;
var rttFramebuffer = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, rttFramebuffer);
rttFramebuffer.width = this.canvas.width;
rttFramebuffer.height = this.canvas.height;
var rttTexture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, rttTexture);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_NEAREST);
gl.generateMipmap(gl.TEXTURE_2D);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, rttFramebuffer.width, rttFramebuffer.height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, rttTexture, 0);
gl.bindTexture(gl.TEXTURE_2D, null);
gl.bindRenderbuffer(gl.RENDERBUFFER, null);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
return rttFrameBuffer;
}
this.setupTexture = function(canvas, textureUnit, uniformName) {
var gl = this.context;
var tex = gl.createTexture();
this.updateTextureFromCanvas(tex, canvas, textureUnit);
tex.width = canvas.width;
tex.height= canvas.height;
// Set the parameters so we can render any size image.
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.useProgram(this.program);
var location = gl.getUniformLocation(this.program, uniformName);
gl.uniform1i(location, textureUnit);
gl.useProgram(this.cellProgram);
location = gl.getUniformLocation(this.cellProgram, uniformName);
gl.uniform1i(location, textureUnit);
return tex;
}
this.updateTextureFromCanvas = function(tex, canvas, textureUnit) {
if(!this.context)return;
var gl = this.context;
gl.activeTexture(gl.TEXTURE0 + textureUnit);
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, canvas);
}
this.createBlankTexture = function(gl, dataArray, type, width, height, uniformName) {
var dataTypedArray = new Uint8Array(dataArray); // Don't need to do this if the data is already in a typed array
for( var i=0 ; i<dataArray ; i+=4 )
{
dataTypedArray[i+3] = 255;
}
var texture = gl.createTexture();
texture.width = width;
texture.height= height;
gl.activeTexture(gl.TEXTURE0 + this.texture.length);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, 0, type, width, height, 0, type, gl.UNSIGNED_BYTE, dataTypedArray);
// Other texture setup here, like filter modes and mipmap generation
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.useProgram(this.program);
var location = gl.getUniformLocation(this.program, uniformName);
gl.uniform1i(location, this.texture.length);
gl.useProgram(this.cellProgram);
location = gl.getUniformLocation(this.cellProgram, uniformName);
gl.uniform1i(location, this.texture.length);
return texture;
}
this.setRectangle = function(gl, x, y, width, height) {
var x1 = x;
var x2 = x + width;
var y1 = y;
var y2 = y + height;
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
x1, y1,
x2, y1,
x1, y2,
x1, y2,
x2, y1,
x2, y2]), gl.STATIC_DRAW);
}
}

Okay I managed to get things working.
I had to learn what exactly needs to be called at different stages:
Do I have to create separate buffers per webgl program?
And I had to change the part with the framebuffer to use a different texture than the one it is putting the data into.
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, sTexture, 0);
gl.activeTexture(gl.TEXTURE0 + 1);
gl.bindTexture(gl.TEXTURE_2D, sTexture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA,
sTexture.width, sTexture.height, 0,
gl.RGBA, gl.UNSIGNED_BYTE, pixels);
so the sTexture needs to change like so:
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, someOtherTexture, 0);

I am using webgl and what I want to do is first render to a texture, then use that texture to render on screen, and I encounter a problem with an attribute in the first step render.
I will try to explain in a few words what I am trying to do. First I want to use a fragment shader to render to a texture something that uses an attribute, then use that texture to render to screen, and repeat the steps for the next frame. But when I try to render with the framebuffer bound that attribute (pos) has invalid values, I mean, no value at all.
I wrote a little demo that shows my problem:
var canvas = document.getElementById("c");
var gl = getWebGLContext(canvas);
var program_init, program_pers, tex, fb;
function init() {
var verts = [
1, 1,
-1, 1,
-1, -1,
1, 1,
-1, -1,
1, -1,
];
var vertBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(verts), gl.STATIC_DRAW);
gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(0);
tex = gl.createTexture();
fb = gl.createFramebuffer();
program_init = createProgramFromScripts(gl, ["vshader-init", "fshader-init"], ["pos"]);
program_pers = createProgramFromScripts(gl, ["vshader-pers", "fshader-pers"], ["a_position"]);
}
function renderToTexture(gl, time) {
gl.useProgram(program_init);
var timeLocation = gl.getUniformLocation(program_init, 'time');
gl.uniform1f(timeLocation, time);
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
gl.drawArrays(gl.TRIANGLES, 0, 6);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
};
function renderToScreen(gl) {
gl.useProgram(program_pers);
gl.drawArrays(gl.TRIANGLES, 0, 6);
};
init();
requestAnimationFrame(function(){
renderToTexture(gl, arguments[0]);
renderToScreen(gl);
requestAnimationFrame( arguments.callee );
});
canvas { border: 1px solid black; }
body { background-color: darkslategrey }
<script src="http://greggman.github.com/webgl-fundamentals/webgl/resources/webgl-utils.js"></script>
<script id="vshader-init" type="vs/shader">
attribute vec4 pos;
varying vec2 uv;
void main() {
gl_Position = pos;
uv = pos.xy * .5 + .5;
}
</script>
<script id="fshader-init" type="fs/shader">
precision mediump float;
varying vec2 uv;
uniform float time;
void main() {
float t = floor(time / 1000.);
vec3 color;
color.x = sin(t*uv.x);
color.y = tan(t*uv.y);
color.z = cos(t);
gl_FragColor = vec4(color, 1.);
}
</script>
<script id="vshader-pers" type="vs/shader">
attribute vec4 a_position;
varying vec2 v_texcoord;
void main() {
gl_Position = a_position;
v_texcoord = a_position.xy * .5 + .5;
}
</script>
<script id="fshader-pers" type="fs/sahder">
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_sampler;
void main() {
gl_FragColor = texture2D(u_sampler, v_texcoord);
}
</script>
<body>
<canvas id="c" width="400" height="400"></canvas>
</body>
If I comment the line 38,39 from the javascript code (the binding of the frameBuffer) and line 54 (the rendering to screen code, that runs a different program) we can see that it renders corectly and the name "pos" is given the right values.
var canvas = document.getElementById("c");
var gl = getWebGLContext(canvas);
var program_init, program_pers, tex, fb;
function init() {
var verts = [
1, 1,
-1, 1,
-1, -1,
1, 1,
-1, -1,
1, -1,
];
var vertBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(verts), gl.STATIC_DRAW);
gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(0);
tex = gl.createTexture();
fb = gl.createFramebuffer();
program_init = createProgramFromScripts(gl, ["vshader-init", "fshader-init"], ["pos"]);
program_pers = createProgramFromScripts(gl, ["vshader-pers", "fshader-pers"], ["a_position"]);
}
function renderToTexture(gl, time) {
gl.useProgram(program_init);
var timeLocation = gl.getUniformLocation(program_init, 'time');
gl.uniform1f(timeLocation, time);
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
//gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
//gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
gl.drawArrays(gl.TRIANGLES, 0, 6);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
};
function renderToScreen(gl) {
gl.useProgram(program_pers);
gl.drawArrays(gl.TRIANGLES, 0, 6);
};
init();
requestAnimationFrame(function(){
renderToTexture(gl, arguments[0]);
//renderToScreen(gl);
requestAnimationFrame( arguments.callee );
});
canvas { border: 1px solid black; }
body { background-color: darkslategrey }
<script src="http://greggman.github.com/webgl-fundamentals/webgl/resources/webgl-utils.js"></script>
<script id="vshader-init" type="vs/shader">
attribute vec4 pos;
varying vec2 uv;
void main() {
gl_Position = pos;
uv = pos.xy * .5 + .5;
}
</script>
<script id="fshader-init" type="fs/shader">
precision mediump float;
varying vec2 uv;
uniform float time;
void main() {
float t = floor(time / 1000.);
vec3 color;
color.x = sin(t*uv.x);
color.y = tan(t*uv.y);
color.z = cos(t);
gl_FragColor = vec4(color, 1.);
}
</script>
<script id="vshader-pers" type="vs/shader">
attribute vec4 a_position;
varying vec2 v_texcoord;
void main() {
gl_Position = a_position;
v_texcoord = a_position.xy * .5 + .5;
}
</script>
<script id="fshader-pers" type="fs/shader">
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_sampler;
void main() {
gl_FragColor = texture2D(u_sampler, v_texcoord);
}
</script>
<body>
<canvas id="c" width="400" height="400"></canvas>
</body>
I do not know much about how it is supposed to work and I am a bit into the dark. I am sure I'm missing something important, but I can't find anywhere what. Any help will be appreciated.

Your framebuffer texture is 1x1 pixels big. What do you expect to see? You're rendering a single pixel.
Also note that unless your framebuffer is the same size as the canvas you'll want to call gl.viewport and set it to the size of the thing you rendering after each call to gl.bindFramebuffer
You probably also want to not create the texture every frame. Here's your code with those things changed.
var canvas = document.getElementById("c");
var gl = canvas.getContext("webgl");
var program_init, program_pers, tex, fb;
var fbWidth = 400;
var fbHeight = 300;
function init() {
var verts = [
1, 1,
-1, 1,
-1, -1,
1, 1,
-1, -1,
1, -1,
];
var vertBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(verts), gl.STATIC_DRAW);
gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(0);
tex = gl.createTexture();
fb = gl.createFramebuffer();
program_init = webglUtils.createProgramFromScripts(gl, ["vshader-init", "fshader-init"], ["pos"]);
program_pers = webglUtils.createProgramFromScripts(gl, ["vshader-pers", "fshader-pers"], ["a_position"]);
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, fbWidth, fbHeight, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
// make non power-of-2 texture renderable
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
}
function renderToTexture(gl, time) {
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
gl.viewport(0, 0, fbWidth, fbHeight);
gl.useProgram(program_init);
var timeLocation = gl.getUniformLocation(program_init, 'time');
gl.uniform1f(timeLocation, time);
gl.drawArrays(gl.TRIANGLES, 0, 6);
};
function renderToScreen(gl) {
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
gl.useProgram(program_pers);
gl.drawArrays(gl.TRIANGLES, 0, 6);
};
init();
requestAnimationFrame(function(){
renderToTexture(gl, arguments[0]);
renderToScreen(gl);
requestAnimationFrame( arguments.callee );
});
canvas { border: 1px solid black; }
body { background-color: darkslategrey }
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
<script id="vshader-init" type="vs/shader">
attribute vec4 pos;
varying vec2 uv;
void main() {
gl_Position = pos;
uv = pos.xy * .5 + .5;
}
</script>
<script id="fshader-init" type="fs/shader">
precision mediump float;
varying vec2 uv;
uniform float time;
void main() {
float t = floor(time / 1000.);
vec3 color;
color.x = sin(t*uv.x);
color.y = tan(t*uv.y);
color.z = cos(t);
gl_FragColor = vec4(color, 1.);
}
</script>
<script id="vshader-pers" type="vs/shader">
attribute vec4 a_position;
varying vec2 v_texcoord;
void main() {
gl_Position = a_position;
v_texcoord = a_position.xy * .5 + .5;
}
</script>
<script id="fshader-pers" type="fs/sahder">
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_sampler;
void main() {
gl_FragColor = texture2D(u_sampler, v_texcoord);
}
</script>
<body>
<canvas id="c" width="400" height="400"></canvas>
</body>

I am currently learning webgl and have a question.
I am trying to make a triangle and passing the color info into fragment shader from js file. The following is my js code:
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n'+
'attribute vec4 a_Color;\n'+
'varying vec4 v_Color;\n'+
'void main(){\n'+
'gl_Position = a_Position;\n'+
'v_Color = a_Color;\n'+
'}\n';
var FSHADER_SOURCE =
'precision highp float;\n'+
'varying vec4 v_Color;\n'+
'void main() {\n'+
'gl_FragColor = v_Color;\n'+
'}\n';
function main(){
var canvas = document.getElementById('webgl');
var gl = getWebGLContext(canvas);
if(!gl){
console.log('Error!');
return;
}
//Init shaders.
if(!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)){
console.log('Error!');
return;
}
var vertices = new Float32Array([-0.8, -0.8, 0.8, -0.8, 0.0, 0.8]);
var color = new Float32Array([0.0, 0.0, 1.0, 1.0]);
var buffer_object = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer_object);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(a_Position);
var color_object = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, color_object);
gl.bufferData(gl.ARRAY_BUFFER, color, gl.STATIC_DRAW);
var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(a_Color);
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, 3);
return 0;
}
This have to create a blue triangle but the only thing I see is a canvas filled with black color. Can anyone tell me what's missing?? I created two buffer objects and used one for vertex and the other for color.

There's a lot of issues with your example but... specific problems.
You're only supplying colors for the first vertex.
You have 3 vertices but only 1 color. You should be getting an error for that.
Did you check the JavaScript Console for errors?
You have 3 options to fix that
Provide a color for each vertex
new Float32Array([
0.0, 0.0, 1.0, 1.0,
0.0, 0.0, 1.0, 1.0,
0.0, 0.0, 1.0, 1.0,
]);
Turn off the a_Color attribute and supply a constant value
gl.disableVertexAtttibArray(a_Color);
gl.vertexAttrib4f(a_Color, 0, 0, 1, 1);
Use a uniform instead of an attribute + varying
remove all references of a_Color and v_color and instead have your
fragment shader be
precision highp float;
uniform vec4 u_Color;
void main() {
gl_FragColor = u_Color;
}
Now you'd set the color with
At Init time
// Lookup the location
var u_colorLocation = gl.getUniformLocation(program, "u_Color");
At render time
// Set the uniform
gl.uniform4f(u_colorLocation, 0, 0, 1, 1);
If you choose #2 you'll likely run into another issue that you'll get a warning that attirbute 0 is not enabled because, at least on my computer, a_Color is assigned to attribute 0. Turning it off means it has to be emulated which is slow. The solution is to make sure a_Position is in attribute 0 by calling gl.bindAttribLocation before linking the program.
Other issues:
Your initShader function is apparently creating a program and attaching it to the WebGLRenderContext (gl.program). Most WebGL projects have many shader programs so it would probably be best to just return the program. In other words, instead of
initShader(...);
gl.getAttribLocation(gl.program, ...)
You probably want
var program = initShader(...);
gl.getAttribLocation(program, ...)
You'll need to fix initShader so it returns the program that was created rather than hacking it on to the WebGLRenderingContext.
Also you're using precision highp float. That won't work on many phones. Unless you're sure you need highp it's better to use mediump.

Previously had a color vertex for rendering this small square, now i want to use an image. Im using an image sprite i had lying around that sits at 64x128 wide.
I'm not getting any errors, but nothing is showing up either. First the shaders:
<script id="shader-fs" type="x-shader/x-fragment">
precision mediump float;
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>
For the buffers:
initBuffers: function () {
this.planePositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, this.planePositionBuffer);
var vertices = [
1.0, 1.0, 0.0,
-1.0, 1.0, 0.0,
1.0, -1.0, 0.0,
-1.0, -1.0, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
this.planePositionBuffer.itemSize = 3;
this.planePositionBuffer.numItems = 4;
this.textureBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, this.textureBuffer);
var textureCoords = [
0.0, 1.0,
0.0, 0.0,
1.0, 1.0,
1.0, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
this.textureBuffer.itemSize = 2;
this.textureBuffer.numItems = 4;
}
Initializing the shaders:
initShaders: function () {
this.shader = new Shader("shader");
var shaderProgram = this.shader.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");
}
And the draw call.
draw: function () {
this.resize();
var delta = this.getDeltaTime();
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
mat4.identity(this.mvMatrix);
mat4.identity(this.pMatrix);
mat4.perspective(this.pMatrix, 45 * Math.PI / 180, gl.canvas.clientWidth / gl.canvas.clientHeight, 0.1, 100.0);
mat4.translate(this.pMatrix, this.pMatrix, [0.0, 0.0, -50.0]);
var shaderProgram = this.shader.shaderProgram;
for (var i = 0; i < this.objects.length; i++) {
this.objects[i].update(delta, this.mvMatrix);
}
gl.bindBuffer(gl.ARRAY_BUFFER, this.planePositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, this.planePositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, this.textureBuffer);
gl.vertexAttribPointer(shaderProgram.textureCoordAttribute, this.textureBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, me.loader.getImage('test'));
gl.uniform1i(shaderProgram.samplerUniform, 0);
this.setMatrixUniforms();
gl.drawArrays(gl.TRIANGLE_STRIP, 0, this.planePositionBuffer.numItems);
requestAnimationFrame(this.draw.bind(this));
},
I based the texture coords off of an article i found on opengles drawing on android. The idea was the coords should be in order of bottom left -> top left -> bottom right -> top right.
Full source code for its broken state can be found here in addition to the snippets above: https://github.com/agmcleod/webgl-2dexperiment/tree/13f31f70037fdd4515c1336423337a1e82ab4e89

Looks as if the WebGL code was all correct. However, I was never invoking the function bindAllTextures to actually set up the texture with webgl for rendering.