Develop Reference

Textures have a black color regardless of the data I put in them

I tryed to put data in the fragment shader to color 2 triangles through textures, but the color given is black (maybe default?), not green or red as expected.
The source from where I tryed to do that is https://webglfundamentals.org/webgl/lessons/webgl-shaders-and-glsl.html#textures-in-fragment-shaders. I put everything from there in my source and I thought that if I put a green pixel with a red pixel in my texture, then it needs to have a different color than black, but was black.
That's the fragment shader:
precision mediump float;
uniform sampler2D u_texture;
void main() {
vec2 texcoord = vec2(0.5, 0.5) // get a value from the middle of the texture
gl_FragColor = texture2D(u_texture, texcoord);
}
There I created the texture and I put data in it.
var tex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex);
var level = 0;
var width = 2;
var height = 1;
var data = new Uint8Array([
255, 0, 0, 255, // a red pixel
0, 255, 0, 255, // a green pixel
]);
gl.texImage2D(gl.TEXTURE_2D, level, gl.RGBA, width, height, 0, gl.RGBA, gl.UNSIGNED_BYTE, data);
I tried to put different data in the texture with even another colors, but the result was the same.

You've to set the texture minifying function to a "non mipmap" filter, else the texture is not mipmap complete. e.g.:
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
By default the minifing parameter is NEAREST_MIPMAP_LINEAR. This parameter value requires a mipmap for the texture, to be complete.
The other option is to generate mipmaps by:
gl.generateMipmap(gl.TEXTURE_2D)
But for that the width and the height of the texture have to be a power of two (for WebGL 1.0). See WebGL specification - 5.13.8 Texture objects.
Note, if a texture is not mipmap complete, then the return value of a texel fetch is (0, 0, 0, 1), this causes the "black" color.

Texture Coordinates are slightly off when rendering to FBO texture

I'm working on a WebGL OpenGL ES project that renders my scene to a texture and then uses that texture to render to the window.
I noticed that this causes an odd shimmering on the edges of textures. When I revert the project back to rendering directly to the window the shimmering goes away.
The FBO is set to the same size as the window and the texture is drawn to the window pixel for pixel.
What is causing this to happen? Is it fixable? I am using GL_NEAREST on the FBO texture and GL_LINEAR on all other textures. I'd rather not use GL_CLAMP_TO_EDGE as that would cause other problems.
[
Framebuffer creation
/* Returns true if a framebuffer object is created */
Display.prototype.createFramebuffer = function(name) {
var gl = this.gl; // Sanity Save
var size = 1024;
var fb = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
fb.width = size;
fb.height = size;
var tex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, fb.width, fb.height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
var rb = gl.createRenderbuffer();
gl.bindRenderbuffer(gl.RENDERBUFFER, rb);
gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, fb.width, fb.height);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, rb);
if(gl.checkFramebufferStatus(gl.FRAMEBUFFER) !== gl.FRAMEBUFFER_COMPLETE) { return false; }
this.fbo[name] = {fb: fb, rb: rb, tex: tex};
gl.bindTexture(gl.TEXTURE_2D, null);
gl.bindRenderbuffer(gl.RENDERBUFFER, null);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
return true;
};
Before drawing scene
/* Draw Geometry */
gl.bindFramebuffer(gl.FRAMEBUFFER, this.fbo.world.fb); // Enable world framebuffer
gl.viewport(0, 0, this.window.width, this.window.height); // Resize to canvas
gl.clearColor(0.5, 0.5, 0.5, 1.0); // Opaque grey backdrop

After a push in the right direction (and plenty of trial and error) I figured out the problem.
The reason this is happening is because hardware anti-aliasing is disabled when rendering to an FBO texture. In order to fix it you need to implement your own AA.
To fix this for my project I attempted a crude MSAA post shader in combination with upscaling my FBO render to 2x the window resolution and that reduced the shimmering to a nearly unnoticeable level.
FXAA might be another good solution but I couldn't get it to work for me personally.
If there are some better ways to go about this let me know!

How to save a value inside a fragment shader to use it later?

I want to save a calculated value from fragment shader in some variable ,so that I would be able to use it next time.
Currently, I am preparing a image using a huge algorithm and I want to save it to some vec4 and , once requested again , I want to just get that vec4 and should say
gl_FragColor = vec4(previously saved variable)
This question is related to another question here which is also asked by me , but I feel that if this question has a answer then I can easily crack the other one.
Any suggestions ?

Fragment shaders in WebGL write to 1 of 2 things. Either (1) the canvas to (2) the attachments of a framebuffer. The attachments of a framebuffer can be textures. Textures can be used as inputs to a shader. Therefore you can write to a texture and use that texture in your next draw.
Here's an example
var vs = `
attribute vec4 position;
void main() {
gl_Position = position;
}
`;
var fs = `
precision mediump float;
uniform sampler2D u_texture;
void main() {
// just grab the middle pixel(s) from the texture
// but swizzle the colors g->r, b->g, r->b
gl_FragColor = texture2D(u_texture, vec2(.5)).gbra;
}`;
var canvas = document.querySelector("canvas");
var gl = canvas.getContext("webgl");
var program = twgl.createProgramFromSources(gl, [vs, fs]);
var positionLocation = gl.getAttribLocation(program, "position");
// we don't need to look up the texture's uniform location because
// we're only using 1 texture. Since the uniforms default to 0
// it will use texture 0.
// put in a clipspace quad
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
-1, -1,
1, -1,
-1, 1,
-1, 1,
1, -1,
1, 1,
]), gl.STATIC_DRAW);
gl.enableVertexAttribArray(positionLocation);
gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);
// make 2 1x1 pixel textures and put a red pixel the first one
var tex1 = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex1);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA,
gl.UNSIGNED_BYTE, new Uint8Array([255, 0, 0, 255]));
var tex2 = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex2);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA,
gl.UNSIGNED_BYTE, null);
// make a framebuffer for tex1
var fb1 = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, fb1);
// attach tex1
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0,
gl.TEXTURE_2D, tex1, 0);
// check this will actually work
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) !==
gl.FRAMEBUFFER_COMPLETE) {
alert("this combination of attachments not supported");
}
// make a framebuffer for tex2
var fb2 = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, fb2);
// attach tex2
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0,
gl.TEXTURE_2D, tex2, 0);
// check this will actually work
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) !==
gl.FRAMEBUFFER_COMPLETE) {
alert("this combination of attachments not supported");
}
function render() {
gl.useProgram(program);
// render tex1 to the tex2
// input to fragment shader
gl.bindTexture(gl.TEXTURE_2D, tex1);
// output from fragment shader
gl.bindFramebuffer(gl.FRAMEBUFFER, fb2);
gl.viewport(0, 0, 1, 1);
gl.drawArrays(gl.TRIANGLES, 0, 6);
// render to canvas so we can see it
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// input to fragment shader, the texture we just rendered to
gl.bindTexture(gl.TEXTURE_2D, tex2);
gl.drawArrays(gl.TRIANGLES, 0, 6);
// swap which texture we are rendering from and to
var t = tex1;
tex1 = tex2;
tex2 = t;
var f = fb1;
fb1 = fb2;
fb2 = f;
requestAnimationFrame(render);
}
requestAnimationFrame(render);
<script src="https://twgljs.org/dist/twgl-full.min.js"></script>
<canvas></canvas>
The sample above puts red in a texture. It then renders that texture by swizzling the color. Green goes to the red channel, Blue goes to the green channel, Red goes to the Blue channel.
I makes 2 textures and attaches them to 2 framebuffers.
First iteration
tex1 = red
tex2 = 0,0,0,0
render to fb2
tex2 is now blue (because red was copied to blue)
render tex2 to canvas (canvas is now green because blue is copied to green)
switch which textures we're rendering to
Second iteration
tex1 = blue (was tex2 last time)
tex2 = red (was tex1 last time)
render to fb2 (was fb1 last time)
tex2 = green (because blue is copied to green)
render tex2 to canvas (canvas is now red because green is copied to red)
switch which textures we're rendering to

Fragment shader executes per fragment(pixel).And as any other shader it cannot store values by default, as you would expect in regular programming language.
There are several ways to do what you want:
You can use imageLoad/Store ,which allows you to read and write data from shader into image.Image uses GL textures as memory storage.What is good about it is that you can store and load numeric data without losing precision when using images because texture filtering is disabled when accessing texture data via image.
Another way to store and read data in shaders is using buffers.Uniform buffers,or since GL4.3 Shader storage buffers..
SSBO allows to read and write huge amount of data.It is really up to you to decide which of those to use for storing and retrieving your data in the shaders.Some people say texture memory access is faster on some hardware.From my experience,using SSBO vs image load store,I haven't found significant difference in performance on Nvidia GPUs.
In your scenario I would probably go with Image Load/Store.Because you can use the same UV indexing into image data as you do into sampled texture.
Also,I don't really know what version of OpenGL you are using ,but to use these extensions you must use GL4.2 and GL4.3.

Unable to render to framebuffer (texture)

I'm trying to implement shadows using shadow maps, so I need to render a scene to a separate framebuffer (texture). I cannot get it to work properly, so after stripping down my codebase I'm left with a relatively simple set of instructions which should render a scene to a texture, and then simply render the texture.
The program consists of two programs:
Ground program
Teapot program
The first should render a rectangle, with a certain texture. The second one should render a teapot (with colors based on its position). Eech render step does the following (well, that's the idea anyway):
Switch to framebuffer
Render teapot
Switch to normal buffer
Render teapot
Render ground
Now, the ground fragment shader looks like:
gl_FragColor = texture2D(shadowMap, fTexCoord);
'shadowMap' is the texture I render to in step 2. I expect to see a floating teapot with a rectangle drawn under it. That indeed works. Now, I also expect to have the 'ground' to contain a teapot. After all, we rendered the scene we are looking at without the ground to the framebuffer/texture.
Code
var UNSIGNED_SHORT_SIZE = 2;
// Variables filled by setup()
var glCanvas;
var gl, teapotProgram, groundProgram;
var vBuffer, iBuffer, fBuffer;
var vertices, indices, textures;
var teapot = null;
var model;
var view;
var light;
var projection;
var BASE_URL = "https://hmbastiaan.nl/martijn/webgl/W08P02_SO/";
var WIDTH = 150, HEIGHT = 150;
function makeTeapot(){
var drawingInfo = teapot.getDrawingInfoObjects();
var indices = drawingInfo.indices;
for(var i=0; i < indices.length; i++){
indices[i] += 4; // Add offset for 'ground'
}
return {
indices: drawingInfo.indices,
vertices: drawingInfo.vertices
}
}
function makeRectangle(x1, x2, y1, y2, z1, z2){
var x1 = -2,
x2 = 2,
y1 = -1,
y2 = -1,
z1 = -1,
z2 = -5;
var vertices = [
vec4(x1, y2, z1, 1),
vec4(x2, y1, z1, 1),
vec4(x2, y1, z2, 1),
vec4(x1, y2, z2, 1)
];
var textures = [
vec2(-1.0, -1.0),
vec2( 1.0, -1.0),
vec2( 1.0, 1.0),
vec2(-1.0, 1.0)
];
var indices = [
0, 1, 2,
0, 2, 3
];
return {
indices: indices,
vertices: vertices,
textures: textures
}
}
function resetBuffers(){
vertices = [];
indices = [];
textures = [];
// Add rectangle
var rectangle = makeRectangle();
Array.prototype.push.apply(vertices, rectangle.vertices);
Array.prototype.push.apply(indices, rectangle.indices);
Array.prototype.push.apply(textures, rectangle.textures);
// Add teapot
var teapot = makeTeapot();
Array.prototype.push.apply(vertices, teapot.vertices);
Array.prototype.push.apply(indices, teapot.indices);
console.log(vertices);
console.log(indices);
console.log(textures);
// Send to GPU
gl.bindBuffer(gl.ARRAY_BUFFER, vBuffer);
gl.bufferData(gl.ARRAY_BUFFER, flatten(vertices), gl.STATIC_DRAW);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, iBuffer);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(indices), gl.STATIC_DRAW);
}
function setup(){
$.get(BASE_URL + "teapot.obj", function(teapot_obj_data){
teapot = new OBJDoc(BASE_URL + "teapot.obj");
if(!teapot.parse(teapot_obj_data, 1)){
alert("Parsing teapot.obj failed.");
return;
}
setup2();
}).fail(function(){
alert("Getting teapot.obj failed.");
});
}
function setup2(){
glCanvas = document.getElementById("gl-canvas");
gl = WebGLUtils.setupWebGL(glCanvas, {stencil: true, alpha: false});
gl.viewport(0, 0, WIDTH, HEIGHT);
teapotProgram = initShaders(gl, BASE_URL + "vshader-teapot.glsl", BASE_URL + "fshader-teapot.glsl");
groundProgram = initShaders(gl, BASE_URL + "vshader-ground.glsl", BASE_URL + "fshader-ground.glsl");
light = vec3(0.0, 2.0, -2.0);
view = lookAt(vec3(0, 0, 3), vec3(0,0,0), vec3(0,1,0));
projection = perspective(45, 1.0, 1, 100.0);
// Get teapot uniforms
gl.useProgram(teapotProgram);
teapotProgram.modelLoc = gl.getUniformLocation(teapotProgram, "Model");
teapotProgram.viewLoc = gl.getUniformLocation(teapotProgram, "View");
teapotProgram.projectionLoc = gl.getUniformLocation(teapotProgram, "Projection");
// Upload uniforms
gl.uniformMatrix4fv(teapotProgram.projectionLoc, false, flatten(projection));
gl.uniformMatrix4fv(teapotProgram.viewLoc, false, flatten(view));
gl.uniformMatrix4fv(teapotProgram.modelLoc, false, flatten(scalem(0.25, 0.25, 0.25)));
// Get teapot attributes
teapotProgram.vPosition = gl.getAttribLocation(teapotProgram, "vPosition");
// Get ground uniforms
gl.useProgram(groundProgram);
groundProgram.modelLoc = gl.getUniformLocation(groundProgram, "Model");
groundProgram.viewLoc = gl.getUniformLocation(groundProgram, "View");
groundProgram.projectionLoc = gl.getUniformLocation(groundProgram, "Projection");
groundProgram.shadowMap = gl.getUniformLocation(groundProgram, "shadowMap");
// Get ground attributes
groundProgram.vTexCoord = gl.getAttribLocation(groundProgram, "vTexCoord");
groundProgram.vPosition = gl.getAttribLocation(groundProgram, "vPosition");
// Allocate and fill vertices buffer
vBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vBuffer);
gl.vertexAttribPointer(teapotProgram.vPosition, 4, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(teapotProgram.vPosition);
gl.vertexAttribPointer(groundProgram.vPosition, 4, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(groundProgram.vPosition);
// Allocate indices buffer
iBuffer = gl.createBuffer();
// Setup FBO
fBuffer = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, fBuffer);
fBuffer.renderbuffer = gl.createRenderbuffer();
gl.bindRenderbuffer(gl.RENDERBUFFER, fBuffer.renderbuffer);
gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, 512, 512);
fBuffer.texture = gl.createTexture();
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, fBuffer.texture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 512, 512, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
gl.generateMipmap(gl.TEXTURE_2D);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST_MIPMAP_LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, fBuffer.texture, 0);
gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, fBuffer.renderbuffer);
// Sanity checking: framebuffer seems to throw now errors
if (!gl.isFramebuffer(fBuffer)) {
throw("Invalid framebuffer");
}
var status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
switch (status) {
case gl.FRAMEBUFFER_COMPLETE:
break;
case gl.FRAMEBUFFER_INCOMPLETE_ATTACHMENT:
throw("Incomplete framebuffer: FRAMEBUFFER_INCOMPLETE_ATTACHMENT");
break;
case gl.FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT:
throw("Incomplete framebuffer: FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT");
break;
case gl.FRAMEBUFFER_INCOMPLETE_DIMENSIONS:
throw("Incomplete framebuffer: FRAMEBUFFER_INCOMPLETE_DIMENSIONS");
break;
case gl.FRAMEBUFFER_UNSUPPORTED:
throw("Incomplete framebuffer: FRAMEBUFFER_UNSUPPORTED");
break;
default:
throw("Incomplete framebuffer: " + status);
}
// Set ground textures
gl.uniform1i(groundProgram.shadowMap, 0);
// Upload uniforms
gl.uniformMatrix4fv(groundProgram.projectionLoc, false, flatten(projection));
gl.uniformMatrix4fv(groundProgram.viewLoc, false, flatten(view));
gl.uniformMatrix4fv(groundProgram.modelLoc, false, flatten(mat4()));
// Restore default buffers
gl.bindTexture(gl.TEXTURE_2D, null);
gl.bindRenderbuffer(gl.RENDERBUFFER, null);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
// Set background colour
gl.clearColor(0.3921, 0.5843, 0.9294, 1.0);
gl.enable(gl.DEPTH_TEST);
gl.enable(gl.CULL_FACE);
resetBuffers();
window.requestAnimationFrame(render);
}
function render(){
var teapot = makeTeapot();
gl.useProgram(teapotProgram);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);
// Switch to framebuffer
gl.bindFramebuffer(gl.FRAMEBUFFER, fBuffer);
// Draw teapot
teapot = makeTeapot();
gl.drawElements(gl.TRIANGLES, teapot.indices.length, gl.UNSIGNED_SHORT, 6 * UNSIGNED_SHORT_SIZE);
// Set framebuffer to defualt buffer (in-browser output)
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
// Draw ground
gl.useProgram(groundProgram);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
// Render teapot
gl.useProgram(teapotProgram);
gl.drawElements(gl.TRIANGLES, teapot.indices.length, gl.UNSIGNED_SHORT, 6 * UNSIGNED_SHORT_SIZE);
}
setup();
<div>
<br/>
<canvas width="150" height="150" id="gl-canvas">Sorry :|</canvas>
</div>
<script type='text/javascript' src="https://code.jquery.com/jquery-2.1.4.min.js"></script>
<script type='text/javascript' src="https://hmbastiaan.nl/martijn/webgl/angel/webgl-utils.js"></script>
<script type='text/javascript' src="https://hmbastiaan.nl/martijn/webgl/angel/initShaders2.js"></script>
<script type='text/javascript' src="https://hmbastiaan.nl/martijn/webgl/angel/MV.js"></script>
<script type='text/javascript' src="https://hmbastiaan.nl/martijn/webgl/angel/objParser.js"></script>
Functions of interest:
setup2(): sets up all the buffers and uniforms.
render(): renders the scene.
Disclaimer: this is for an assignment, although this code is simplified enough to not look like the original assignment at all :).

At a glance there are several issues.
Texture bindings are global. Since in setup2 you unbind the 1 texture that means it's never used.
You need to bind whatever textures are needed before each draw call. In other words when you draw the ground you need to bind the teapot texture as in
gl.bindTexture(gl.TEXTURE_2D, fBuffer.texture);
Note: This is an over simplification of what's really needed. You really need to
Choose a texture unit to bind the texture to
var unit = 5;
gl.activeTexture(gl.TEXTURE0 + unit);
Bind the texture to that unit.
gl.bindTexture(gl.TEXTURE_2D, fBuffer.texture);
Set the uniform sampler to that texture unit
gl.uniform1i(groundProgram.shadowMap, unit);
The reason you don't need those extra steps is because (a) you only
have 1 texture so you're using texture unit #0, the default and (b) because
uniforms default to 0 so shadowMap is looking at texture unit #0.
Because you've made a mipmapped texture just rendering to level 0 will not update the mips.
In other words after you render the teapot you'll have a teapot in mip level 0 but mip levels 1, 2, 3, 4, 5 etc will still have nothing in them. You need to call
gl.generateMipmap(gl.TEXTURE_2D)
For that texture after you've rendered the teapot to it. Either that or stop using mips
You need to set the viewport every time you call gl.bindFramebuffer.
gl.bindFramebuffer should almost always be followed by a call to gl.viewport to make the viewport match the size of the thing you're rendering to
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
// set to size of fb
gl.viewport(0, 0, widthOfFb, heightOfFb);
renderSomething();
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
// set to size of canvas's drawingBuffer
gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
Attributes settings are global
You setup the teapot attributes. Then you draw a teapot to the texture. You then draw ground, but you're still using the teapot attributes.
Just like textures you need to setup attributes before each draw call.
I'm also guessing you really should not be calling makeTeapot in your render function but instead it should be called in setup.
You might find this article useful
You should also consider not putting properties on WebGL objects as it's arguably an anti-pattern.
Also synchronous XHR requests are not cool. You're getting this message in the JavaScript console
Synchronous XMLHttpRequest on the main thread is deprecated because
of its detrimental effects to the end user's experience. For more
help, check http://xhr.spec.whatwg.org/.

WebGL Texture resize unexpected output

When using textures in WebGL, sometimes I need to make them larger than they were originally. When I do that, it causes the textures to appear differently, especially on lighter backgrounds.
I have the following image (256 x 256):
When rendered in WebGL, it is slightly larger than the original image. Here is how the image appears on two different backgrounds:
As you can see, the image appears correctly on the dark background, but when on the light background, has a white outline.
My setup code:
gl.clearColor(0x22 / 0xFF, 0x22 / 0xFF, 0x22 / 0xFF, 1); // set background color
gl.enable(gl.BLEND); // enable transparency
gl.disable(gl.DEPTH_TEST); // disable depth test (causes problems with alpha if enabled)
gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA); //set up blending
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT); //clear the gl canvas
gl.viewport(0, 0, canvas.width, canvas.height); //set the viewport
And this is the code called every time a texture is loaded:
function handleTextureLoaded(image, texture) {
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
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.bindTexture(gl.TEXTURE_2D, null);
loadCount++;
}
What is causing the outline to appear, and how do I fix it?
NOTE: When I put the original image on these same two backgrounds, this problem does not occur, even when I resize the image.
I tried disabling the alpha on the WebGL context (as told by #zfedoran):
gl = canvas.getContext('webgl', {antialias: false, alpha: false })
|| canvas.getContext('experimental-webgl', {antialias: false, alpha: false });
And a small blank border now appears around the image, like this (enlarged):

On top of the canvas's alpha as mentioned by #zfedoran how do you make the original image?
I believe the issue is as follows
Let's say you have an anti-aliased edge like this. What color is this pixel?
Assume the main color, the color of the pixels in the bottom right, was 1,0,0 (pure red). Ideally the pixel pointed to by the arrow would be (1,0,0,0.5). In other words, pure red with an alpha of 0.5. But, depending how on the image was created to generate that anti-aliased pixel it might have been blended with the purely transparent pixels next to it so it no longer pure red. Those purely transparent pixels are likely (0,0,0,0) which is transparent black.
Even if your drawing program handles this correctly, GL likely does not. When you draw an image with texture filtering on (gl.LINEAR etc) GL is going to average the pixels near each other, some of those pixels are transparent black. Blending black with red gives dark red. Hence you get a dark border.
Here you can see the issue
"use strict";
function main() {
var planeVertices = [
-1, -1,
1, -1,
-1, 1,
1, 1,
];
var texcoords = [
0, 1,
1, 1,
0, 0,
1, 0,
];
var indices = [
0, 1, 2,
2, 1, 3,
];
var canvas = document.getElementById("c");
var gl = canvas.getContext("webgl", {alpha:false});
var programs = {}
programs.normalProgram = twgl.createProgramFromScripts(
gl, ["2d-vertex-shader", "2d-fragment-shader"], ["a_position", "a_texcoord"]);
programs.preMultiplyAlphaProgram = twgl.createProgramFromScripts(
gl, ["2d-vertex-shader", "pre-2d-fragment-shader"], ["a_position", "a_texcoord"]);
var positionLoc = 0; // assigned in createProgramsFromScripts
var texcoordLoc = 1; // assigned in createProgramsFromScripts
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(planeVertices),
gl.STATIC_DRAW);
gl.enableVertexAttribArray(positionLoc);
gl.vertexAttribPointer(positionLoc, 2, gl.FLOAT, false, 0, 0);
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(texcoords),
gl.STATIC_DRAW);
gl.enableVertexAttribArray(texcoordLoc);
gl.vertexAttribPointer(texcoordLoc, 2, gl.FLOAT, false, 0, 0);
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffer);
gl.bufferData(
gl.ELEMENT_ARRAY_BUFFER,
new Uint16Array(indices),
gl.STATIC_DRAW);
var img = new Image();
img.onload = createTextures;
img.src = document.getElementById("i").text;
function createTexture() {
var tex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, img);
gl.generateMipmap(gl.TEXTURE_2D); // assuming power-of-2
return tex;
}
var textures = {};
function createTextures() {
gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, false);
textures.unpremultipliedAlphaTexture = createTexture();
gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, true);
textures.premultipliedAlphaTexture = createTexture();
document.body.appendChild(document.createElement("hr"));
insert("original image");
document.body.appendChild(img);
render();
}
function insert(text) {
var pre = document.createElement("pre");
pre.appendChild(document.createTextNode(text));
document.body.appendChild(pre);
};
function grabImage(prg, blend, texName) {
document.body.appendChild(document.createElement("hr"));
insert(
"gl.useProgram(" + prg + ")\n" +
"gl.blendFunc(gl." + blend.src + ", gl." + blend.dst + ")\n" +
"gl.bindTexture(gl.TEXTURE2D, " + texName + ")");
var img = new Image();
img.src = gl.canvas.toDataURL();
document.body.appendChild(img);
};
function render() {
gl.enable(gl.BLEND);
Object.keys(programs).forEach(function(p, pndx) {
gl.useProgram(programs[p]);
[
{ src: "SRC_ALPHA", dst: "ONE_MINUS_SRC_ALPHA" },
{ src: "ONE", dst: "ONE_MINUS_SRC_ALPHA" },
].forEach(function(b, bndx) {
gl.blendFunc(gl[b.src], gl[b.dst]);
Object.keys(textures).forEach(function(texName, tndx) {
gl.bindTexture(gl.TEXTURE_2D, textures[texName]);
gl.clearColor(0x3D/0xFF, 0x87/0xFF, 0xEA/0xFF, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
grabImage(p, b, texName);
});
});
});
}
}
main();
canvas {
border: 1px solid black;
display: none;
}
img {
background-color: #3D87EA;
border: 1px solid black;
width: 256px;
height: 256px;
}
<script src="https://twgljs.org/dist/3.x/twgl.min.js"></script>
<!-- vertex shader -->
<script id="2d-vertex-shader" type="x-shader/x-vertex">
attribute vec4 a_position;
attribute vec2 a_texcoord;
varying vec2 v_texcoord;
void main() {
gl_Position = a_position;
v_texcoord = a_texcoord;
}
</script>
<!-- fragment shaders -->
<script id="2d-fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_texture;
void main() {
gl_FragColor = texture2D(u_texture, v_texcoord);
}
</script>
<script id="pre-2d-fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_texture;
void main() {
vec4 textureColor = texture2D(u_texture, v_texcoord);
gl_FragColor = vec4(textureColor.rgb * textureColor.a, textureColor.a);
}
</script>
<canvas id="c" width="32" height="32"></canvas>
<script type="not-js" id="i">data:image/png;base64,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</script>
There's a few solutions
Make sure transparent area actually has color in.
In other words, if all the pixels in the top left of the image above are RED with 0 alpha then when the pixels get filtered they'll be blending (1,0,0,0) transparent red instead of (0,0,0,0) transparent black. Unfortunately there's no easy way to do this in most drawing programs.
There's a plugin for Photoshop that lets you do it called SuperPNG It lets you create a 4th channel for the alpha instead of using photoshop's transparency. That lets you set the alpha separate from the image.
In your case you'd end up with an image with layers like this
Now there are no bad colors to blend with.
Switch to pre-multiplied alpha
In this case before calling gl.texImage2D to upload the image call
gl.pixelStorei(UNPACK_PREMULTIPLY_ALPHA_WEBGL, true);
before calling gl.texImage2D. That tells WebGL to multiply the colors by their alpha when the image is loaded. You then use blending with
gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
Turn off filtering in GL
gl.texParameter(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameter(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
Assuming your source image doesn't have any bad colors this means GL won't making new bad colors as it filters but of course it also means if you scale or rotate the image you'll get aliasing.
Create your own mips
Most apps use gl.genereateMipmap to generate mips but you can generate them yourself offline and upload them yourself. That's not a perfect solution either but it does let you use `gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_NEAREST);
Combinations of the above

Have you tried disabling the alpha on the WebGL context?
var gl = this.canvas.getContext('webgl', {antialias: false, alpha: false })
|| this.canvas.getContext('experimental-webgl', {antialias: false, alpha: false });