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After a lot of searching, I managed to get the texSubImage2D function to work. Simply what I haven't found is: what is this function for. In the example below I made a nice effect. In short, I know how to make it work but I am still completely unaware of the role of its parameters. And where to find these explanations?
I'm not looking for the syntax,
the example I give shows that I have (it seems to me) understood it well.
https://registry.khronos.org/webgl/specs/latest/1.0/#5.14.8
What I don't understand at all is the semantics...
Anyway, if someone could answer with examples so that I can understand.
"use strict";
let canvas = document.getElementById("canvas");
let gl = canvas.getContext("webgl");
gl.canvas.width = 30;
gl.canvas.height = 30;
let vertex = `
attribute vec2 a_position;
attribute vec2 a_texCoord;
uniform vec2 u_resolution;
varying vec2 v_texCoord;
void main() {
vec2 zeroToOne = a_position / u_resolution;
vec2 zeroToTwo = zeroToOne * 2.0;
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
v_texCoord = a_texCoord;
}
`;
let fragment = `
precision mediump float;
uniform sampler2D u_image;
varying vec2 v_texCoord;
void main() {
gl_FragColor = texture2D(u_image, v_texCoord);
gl_FragColor.rgb *= gl_FragColor.a;
}
`;
let shader = gl.createProgram();
const vertexShader = gl.createShader(gl.VERTEX_SHADER);
const fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(vertexShader, vertex);
gl.shaderSource(fragmentShader, fragment);
gl.compileShader(vertexShader);
gl.compileShader(fragmentShader);
gl.attachShader(shader, vertexShader);
gl.attachShader(shader, fragmentShader);
gl.linkProgram(shader);
let image_RGBA = new Image();
image_RGBA.src = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAB4AAAAeBAMAAADJHrORAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAYUExURdUAAKPTdgCN09Aq0w4A09PS0dOoXwD//56WZMcAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAA8SURBVCjPYyAIBJEBNr4SAmDnG8MALr4LBODmh4IAPn5aWhp+fjkBPgH9BOwn4H4C/icQfgTCHx9gYAAArEg8b+0tf+EAAAAASUVORK5CYII=";
image_RGBA.onload = function() {
go(image_RGBA);
};
function go(image) {
let width = image.width;
let height = image.height;
let positionLocation = gl.getAttribLocation(shader, "a_position");
let texcoordLocation = gl.getAttribLocation(shader, "a_texCoord");
let positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
0, 0,
width, 0,
0, height,
0, height,
width, 0,
width, height
]), gl.STATIC_DRAW);
let 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);
let texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
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);
const canvas2D = document.getElementById('canvas2D');
canvas2D.width = 30;
canvas2D.height = 30;
const ctx = canvas2D.getContext('2d');
ctx.drawImage(image, 0, 0);
var imgData = ctx.getImageData(0, 0, width, height).data;
var ArrayBufferView = new Uint8Array(imgData.buffer);
gl.texImage2D(
gl.TEXTURE_2D,
0,
gl.RGBA,
30,
30,
0,
gl.RGBA,
gl.UNSIGNED_BYTE,
ArrayBufferView
);
gl.texSubImage2D(
gl.TEXTURE_2D,
0,
0,
0,
29,
29,
gl.RGBA,
gl.UNSIGNED_BYTE,
ArrayBufferView
);
let resolutionLocation = gl.getUniformLocation(shader, "u_resolution");
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
gl.clearColor(100 / 255, 200 / 255, 150 / 255, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.useProgram(shader);
gl.enableVertexAttribArray(positionLocation);
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
let size = 2;
let type = gl.FLOAT;
let normalize = false;
let stride = 0;
let offset = 0;
gl.vertexAttribPointer(positionLocation, size, type, normalize, stride, offset);
gl.enableVertexAttribArray(texcoordLocation);
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
size = 2;
type = gl.FLOAT;
normalize = false;
stride = 0;
offset = 0;
gl.vertexAttribPointer(texcoordLocation, size, type, normalize, stride, offset);
gl.uniform2f(resolutionLocation, gl.canvas.width, gl.canvas.height);
gl.enable(gl.BLEND);
gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
gl.drawArrays(gl.TRIANGLES, 0, 6);
}
#canvas {
width: 150px;
height: 150px;
image-rendering: pixelated;
}
#canvas2D {
width: 150px;
height: 150px;
image-rendering: pixelated;
}
<canvas id="canvas2D"></canvas><canvas id="canvas"></canvas>
I'm trying to translate this example from Three.js - https://codepen.io/tutsplus/pen/PZmpEM
to pure WebGL. I experimented a lot with the code, I think there is an error in texture baking, but my attempts are unsuccessful, if not difficult, please!
WebGL example
let a_Position, u_Mouse, u_Sampler, u_Resolution;
const position = {
screenRect: null,
xyz: [0.0, 0.0, 0.0],
mouseDown: false,
};
function main() {
const canvas = document.getElementById('canvas');
const gl = canvas.getContext('webgl');
canvas.width = canvas.clientWidth;
canvas.height = canvas.clientHeight;
const program = webglUtils.createProgramFromScripts(gl, ["2d-vertex-shader", "2d-fragment-shader"]);
gl.useProgram(program);
const tick = function() {
render(gl, canvas, fbo, plane);
window.requestAnimationFrame(tick, canvas);
};
a_Position = gl.getAttribLocation(program, 'a_position');
u_Mouse = gl.getUniformLocation(program, 'u_mouse');
u_Resolution = gl.getUniformLocation(program, 'u_resolution');
u_Sampler = gl.getUniformLocation(program, 'u_sampler');
const fbo = [initFramebufferObject(gl), initFramebufferObject(gl)];
const plane = initVertexBuffersForPlane(gl);
tick();
}
let src = 0, dst = 1, t;
function render(gl, canvas, fbo, plane) {
gl.bindFramebuffer(gl.FRAMEBUFFER, fbo[dst]);
gl.viewport(0, 0, 1, 1);
drawTexture(gl, gl.program, plane, fbo[src].texture);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.viewport(0, 0, canvas.width, canvas.height);
drawTexture(gl, gl.program, plane, fbo[dst].texture);
t = src;
src = dst;
dst = t;
}
function drawTexture(gl, program, o, texture) {
gl.uniform3f(u_Mouse, ...position.xyz);
gl.uniform2f(u_Resolution, canvas.width, canvas.height);
initAttributeVariable(gl, a_Position, o.vertexBuffer);
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, o.indexBuffer);
gl.drawElements(gl.TRIANGLES, o.numIndices, o.indexBuffer.type, 0);
}
function initAttributeVariable(gl, a_attribute, buffer) {
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.vertexAttribPointer(a_attribute, buffer.num, buffer.type, false, 0, 0);
gl.enableVertexAttribArray(a_attribute);
}
function initFramebufferObject(gl) {
const framebuffer = gl.createFramebuffer(), texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, new Uint8Array([0, 0, 0, 255]));
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
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);
framebuffer.texture = texture;
gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.bindTexture(gl.TEXTURE_2D, null);
return framebuffer;
}
function initVertexBuffersForPlane(gl) {
const vertices = new Float32Array([1.0, 1.0, 0.0, -1.0, 1.0, 0.0, -1.0,-1.0, 0.0, 1.0,-1.0, 0.0]);
const texCoords = new Float32Array([1.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0]);
const indices = new Uint8Array([0, 1, 2, 0, 2, 3]);
const o = {};
o.vertexBuffer = initArrayBufferForLaterUse(gl, vertices, 3, gl.FLOAT);
o.indexBuffer = initElementArrayBufferForLaterUse(gl, indices, gl.UNSIGNED_BYTE);
o.numIndices = indices.length;
gl.bindBuffer(gl.ARRAY_BUFFER, null);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
return o;
}
function initArrayBufferForLaterUse(gl, data, num, type) {
const buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW);
buffer.num = num;
buffer.type = type;
return buffer;
}
function initElementArrayBufferForLaterUse(gl, data, type) {
const buffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffer);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, data, gl.STATIC_DRAW);
buffer.type = type;
return buffer;
}
function mouseHandlers() {
function getPosition(e) {
const x = e.clientX, y = window.innerHeight - e.clientY, z = 0.05;
position.xyz = [x, y, z];
}
function getRect() {
position.screnRect = canvas.getBoundingClientRect();
}
function mouseDown(e) {
position.mouseDown = true;
getPosition(e);
}
function move(e) {
if (position.mouseDown) getPosition(e);
else return;
}
function up() {
position.mouseDown = false;
}
getRect();
canvas.addEventListener('mousedown', mouseDown);
canvas.addEventListener('mousemove', move);
canvas.addEventListener('mouseup', up);
}
mouseHandlers();
main();
body {
margin: 0;
}
canvas {
width: 100vw;
height: 100vh;
display: block;
}
<canvas id="canvas"></canvas>
<script id="2d-vertex-shader" type="x-shader/x-vertex">
attribute vec4 a_position;
void main() {
gl_Position = a_position;
}
</script>
<script id="2d-fragment-shader" type="x-shader/x-fragment">
precision mediump float;
uniform sampler2D u_sampler;
uniform vec2 u_resolution;
uniform vec3 u_mouse;
void main() {
vec2 uv = gl_FragCoord.xy / u_resolution;
gl_FragColor = texture2D(u_sampler, uv);
float dist = distance(u_mouse.xy, gl_FragCoord.xy);
gl_FragColor.rgb += u_mouse.z * max(15.0-dist,0.0);
//gl_FragColor.gb += 0.01; /* testing FBO */
}
</script>
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
So I have a result after moving the mouse but something is wrong:
It should be:
There is an obvious mistake when you create the texture objects for the frambuffer.
If you do not generate mipmaps (by gl.generateMipmap), then it is important to set gl.TEXTURE_MIN_FILTER. Since the default filter is gl.NEAREST_MIPMAP_LINEAR the texture would be mipmap incomplete, if you don't change the minifying function to gl.NEAREST or gl.LINEAR:
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, width, height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
See further OpenGL ES 2.0 Full Specification - 3.7.10 Texture Completeness.
I recommend to check the completeness of the framebuffer:
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE) {
// [...]
}
The size of the frame buffer textures has to be a power of 2 (WebGL 1.0). Create framebuffers with a fixed size (e.g. 1024x1024):
framebuffer.size = [1024, 1024];
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, ...framebuffer.size, 0, gl.RGBA, gl.UNSIGNED_BYTE, new Uint8Array(tblack));
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
framebuffer.texture = texture;
gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE) {
alert("incomplete frambuffer");
}
Ensure that the uniforms are set correctly. Set the resolution (u_resolution) dependent on the size of the framebuffer. The position of the mouse (u_mouse) has to be relative to the size of the framebuffer:
function drawTexture(gl, program, o, texture, resolution) {
const mx = position.xyz[0] * resolution[0] / canvas.width;
const my = position.xyz[1] * resolution[1] / canvas.height;
gl.uniform3f(u_Mouse, mx, my, position.xyz[2]);
gl.uniform2f(u_Resolution, resolution[0], resolution[1]);
initAttributeVariable(gl, a_Position, o.vertexBuffer);
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, o.indexBuffer);
gl.drawElements(gl.TRIANGLES, o.numIndices, o.indexBuffer.type, 0);
}
Set the viewport rectangle when you switch the current frame buffer
let src = 0, dst = 1, t;
function render(gl, canvas, fbo, plane) {
gl.bindFramebuffer(gl.FRAMEBUFFER, fbo[dst]);
gl.viewport(0, 0, ...fbo[dst].size);
drawTexture(gl, gl.program, plane, fbo[src].texture, fbo[src].size);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.viewport(0, 0, canvas.width, canvas.height);
drawTexture(gl, gl.program, plane, fbo[dst].texture, [canvas.width, canvas.height]);
t = src;
src = dst;
dst = t;
}
See the example, where the computation of the distance to the mouse is scaled, by the ration of the canvas resoultuion and the framebuffer:
let a_Position, u_Mouse, u_Sampler;
const position = {
screenRect: null,
xyz: [0.0, 0.0, 0.0],
mouseDown: false,
};
function main() {
const canvas = document.getElementById('canvas');
const gl = canvas.getContext('webgl');
canvas.width = canvas.clientWidth;
canvas.height = canvas.clientHeight;
const program = webglUtils.createProgramFromScripts(gl, ["2d-vertex-shader", "2d-fragment-shader"]);
gl.useProgram(program);
const tick = function() {
render(gl, canvas, fbo, plane);
window.requestAnimationFrame(tick, canvas);
};
a_Position = gl.getAttribLocation(program, 'a_position');
u_Mouse = gl.getUniformLocation(program, 'u_mouse');
u_Sampler = gl.getUniformLocation(program, 'u_sampler');
u_Resolution = gl.getUniformLocation(program, 'u_resolution');
u_CanvasSize = gl.getUniformLocation(program, 'u_canvasSize');
const fbo = [initFramebufferObject(gl), initFramebufferObject(gl)];
const plane = initVertexBuffersForPlane(gl);
tick();
}
let src = 0, dst = 1, t;
function render(gl, canvas, fbo, plane) {
gl.bindFramebuffer(gl.FRAMEBUFFER, fbo[dst]);
gl.viewport(0, 0, ...fbo[dst].size);
drawTexture(gl, gl.program, plane, fbo[src].texture, fbo[src].size);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.viewport(0, 0, canvas.width, canvas.height);
drawTexture(gl, gl.program, plane, fbo[dst].texture, [canvas.width, canvas.height]);
t = src;
src = dst;
dst = t;
}
function drawTexture(gl, program, o, texture, resolution) {
const mx = position.xyz[0] * resolution[0] / canvas.width;
const my = position.xyz[1] * resolution[1] / canvas.height;
gl.uniform3f(u_Mouse, mx, my, position.xyz[2]);
gl.uniform2f(u_Resolution, resolution[0], resolution[1]);
gl.uniform2f(u_CanvasSize, canvas.width, canvas.height);
initAttributeVariable(gl, a_Position, o.vertexBuffer);
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, o.indexBuffer);
gl.drawElements(gl.TRIANGLES, o.numIndices, o.indexBuffer.type, 0);
}
function initAttributeVariable(gl, a_attribute, buffer) {
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.vertexAttribPointer(a_attribute, buffer.num, buffer.type, false, 0, 0);
gl.enableVertexAttribArray(a_attribute);
}
function initFramebufferObject(gl) {
let framebuffer = gl.createFramebuffer(), texture = gl.createTexture();
framebuffer.size = [1024, 1024];
let tblack = []
for (let i= 0; i < framebuffer.size[0]*framebuffer.size[1]; i ++) tblack.push(0, 0, 0, 255);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, ...framebuffer.size, 0, gl.RGBA, gl.UNSIGNED_BYTE, new Uint8Array(tblack));
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
framebuffer.texture = texture;
gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE) {
alert("incomplete frambuffer");
}
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.bindTexture(gl.TEXTURE_2D, null);
return framebuffer;
}
function initVertexBuffersForPlane(gl) {
const vertices = new Float32Array([1.0, 1.0, 0.0, -1.0, 1.0, 0.0, -1.0,-1.0, 0.0, 1.0,-1.0, 0.0]);
const texCoords = new Float32Array([1.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0]);
const indices = new Uint8Array([0, 1, 2, 0, 2, 3]);
const o = {};
o.vertexBuffer = initArrayBufferForLaterUse(gl, vertices, 3, gl.FLOAT);
o.indexBuffer = initElementArrayBufferForLaterUse(gl, indices, gl.UNSIGNED_BYTE);
o.numIndices = indices.length;
gl.bindBuffer(gl.ARRAY_BUFFER, null);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
return o;
}
function initArrayBufferForLaterUse(gl, data, num, type) {
const buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW);
buffer.num = num;
buffer.type = type;
return buffer;
}
function initElementArrayBufferForLaterUse(gl, data, type) {
const buffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffer);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, data, gl.STATIC_DRAW);
buffer.type = type;
return buffer;
}
function mouseHandlers() {
function getPosition(e) {
const x = e.clientX, y = window.innerHeight - e.clientY, z = 0.05;
position.xyz = [x, y, z];
}
function getRect() {
position.screnRect = canvas.getBoundingClientRect();
}
function mouseDown(e) {
position.mouseDown = true;
getPosition(e);
}
function move(e) {
if (position.mouseDown) getPosition(e);
else return;
}
function up() {
position.mouseDown = false;
}
getRect();
canvas.addEventListener('mousedown', mouseDown);
canvas.addEventListener('mousemove', move);
canvas.addEventListener('mouseup', up);
}
mouseHandlers();
main();
<style>
body { margin: 0; }
canvas { width: 100vw; height: 100vh; display: block; }
</style>
<script id="2d-vertex-shader" type="x-shader/x-vertex">
attribute vec4 a_position;
void main() {
gl_Position = a_position;
}
</script>
<script id="2d-fragment-shader" type="x-shader/x-fragment">
precision mediump float;
uniform sampler2D u_sampler;
uniform vec2 u_resolution;
uniform vec2 u_canvasSize;
uniform vec3 u_mouse;
void main() {
vec2 uv = gl_FragCoord.xy / u_resolution.xy;
vec4 texColor = texture2D(u_sampler, uv);
vec2 scale = u_canvasSize / u_resolution;
float dist = distance(u_mouse.xy * scale, gl_FragCoord.xy * scale);
float intensity = u_mouse.z * max(15.0-dist,0.0);
gl_FragColor = texColor + vec4(vec3(intensity), 0.0);
}
</script>
<canvas id="canvas"></canvas>
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
var gl, utils, pseudoImg, vertices;
var img = null;
document.addEventListener('DOMContentLoaded', () => {
utils = new WebGLUtils();
vertices = utils.prepareVec2({x1 : -1.0, y1 : -1.0, x2 : 1.0, y2 : 1.0});
gl = utils.getGLContext(document.getElementById('canvas'));
var program = utils.getProgram(gl, 'render-vs', 'render16bit-fs');
var histogramProgram = utils.getProgram(gl, 'histogram-vs', 'histogram-fs');
var sortProgram = utils.getProgram(gl, 'sorting-vs', 'sorting-fs');
var showProgram = utils.getProgram(gl, 'showhistogram-vs', 'showhistogram-fs');
utils.activateTextureByIndex(gl, showProgram, 'histTex', 3);
utils.activateTextureByIndex(gl, showProgram, 'maxTex', 4);
utils.activateTextureByIndex(gl, sortProgram, 'tex3', 2);
utils.activateTextureByIndex(gl, histogramProgram, 'tex2', 1);
utils.activateTextureByIndex(gl, program, 'u_texture', 0);
var vertexBuffer = utils.createAndBindBuffer(gl, vertices);
var imageTexture;
computeHistogram = (AR, myFB) => {
gl.useProgram(histogramProgram);
var width = AR.width;
var height = AR.height;
var numOfPixels = width * height;
var pixelIds = new Float32Array(numOfPixels);
for (var i = 0; i < numOfPixels; i++) {
pixelIds[i] = i;
}
var histogramFbObj = utils.createTextureAndFramebuffer(gl, {
format : gl.RED,
internalFormat : gl.R32F,
filter : gl.NEAREST,
dataType : gl.FLOAT,
mipMapST : gl.CLAMP_TO_EDGE,
width : 256,
height : 256
});
gl.bindFramebuffer(gl.FRAMEBUFFER, histogramFbObj.fb);
gl.viewport(0, 0, 256, 256);
var pixelBuffer = utils.createAndBindBuffer(gl, pixelIds, true);
gl.blendFunc(gl.ONE, gl.ONE);
gl.enable(gl.BLEND);
utils.linkAndSendDataToGPU(gl, histogramProgram, 'pixelIds', pixelBuffer, 1);
gl.uniform2fv(gl.getUniformLocation(histogramProgram, 'imageDimensions'), [width, height]);
utils.sendTextureToGPU(gl, myFB.tex, 1);
gl.drawArrays(gl.POINTS, 0, numOfPixels);
gl.blendFunc(gl.ONE, gl.ZERO);
gl.disable(gl.BLEND);
return histogramFbObj;
};
sortHistogram = (histogramFbObj) => {
gl.useProgram(sortProgram);
utils.linkAndSendDataToGPU(gl, sortProgram, 'vertices', vertexBuffer, 2);
var sortFbObj = utils.createTextureAndFramebuffer(gl, {
format : gl.RED,
internalFormat : gl.R32F,
filter : gl.NEAREST,
dataType : gl.FLOAT,
mipMapST : gl.CLAMP_TO_EDGE,
width : 1,
height : 1
});
gl.bindFramebuffer(gl.FRAMEBUFFER, sortFbObj.fb);
gl.viewport(0, 0, 1, 1);
utils.sendTextureToGPU(gl, histogramFbObj.tex, 2);
gl.drawArrays(gl.TRIANGLES, 0, 6);
return sortFbObj;
};
showHistogram = (histFb, sortFb) => {
gl.useProgram(showProgram);
utils.linkAndSendDataToGPU(gl, showProgram, 'vertices', vertexBuffer, 2);
utils.sendTextureToGPU(gl, histFb.tex, 3);
utils.sendTextureToGPU(gl, sortFb.tex, 4);
gl.uniform2fv(gl.getUniformLocation(showProgram, 'imageDimensions'), [gl.canvas.width, gl.canvas.height]);
gl.drawArrays(gl.TRIANGLES, 0, 6);
};
showTexture = (AR) => {
imageTexture = utils.createAndBindTexture(gl, {
filter : gl.NEAREST,
mipMapST : gl.CLAMP_TO_EDGE,
dataType : gl.UNSIGNED_SHORT,
format : gl.RGBA_INTEGER,
internalFormat : gl.RGBA16UI,
img : AR.img,
width : AR.width,
height : AR.height
});
gl.useProgram(program);
var myFB = utils.createTextureAndFramebuffer(gl, {
filter : gl.NEAREST,
mipMapST : gl.CLAMP_TO_EDGE,
dataType : gl.UNSIGNED_BYTE,
format : gl.RGBA,
internalFormat : gl.RGBA,
width : AR.width,
height : AR.height,
});
gl.bindFramebuffer(gl.FRAMEBUFFER, myFB.fb);
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
utils.linkAndSendDataToGPU(gl, program, 'vertices', vertexBuffer, 2);
gl.uniform1f(gl.getUniformLocation(program, 'flipY'), 1.0);
utils.sendTextureToGPU(gl, imageTexture, 0);
gl.drawArrays(gl.TRIANGLES, 0, 6);
var fb1 = computeHistogram(AR, myFB);
var fb2 = sortHistogram(fb1);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
showHistogram(fb1, fb2);
};
var w = 128;
var h = 128;
var size = w * h * 4;
var img = new Uint16Array(size); // need Uint16Array
for (var i = 0; i < img.length; i += 4) {
img[i + 0] = 65535; // r
img[i + 1] = i/64 * 256; // g
img[i + 2] = 0; // b
img[i + 3] = 65535; // a
}
showTexture({
img : img,
width : w,
height : h
});
});
<script id="render16bit-fs" type="not-js">
#version 300 es
precision highp float;
uniform highp usampler2D tex;
in vec2 texcoord; // receive pixel position from vertex shader
out vec4 fooColor;
void main() {
uvec4 unsignedIntValues = texture(tex, texcoord);
vec4 floatValues0To65535 = vec4(unsignedIntValues);
vec4 colorValues0To1 = floatValues0To65535;
fooColor = colorValues0To1;
}
</script>
<script type="not-js" id="render-vs">
#version 300 es
in vec2 vertices;
out vec2 texcoord;
uniform float flipY;
void main() {
texcoord = vertices.xy * 0.5 + 0.5;
gl_Position = vec4(vertices.x, vertices.y * flipY, 0.0, 1.0);
}
</script>
<script type="not-js" id="histogram-vs">
#version 300 es
in float pixelIds; //0,1,2,3,4,.......width*height
uniform sampler2D tex2;
uniform vec2 imageDimensions;
void main () {
vec2 pixel = vec2(mod(pixelIds, imageDimensions.x), floor(pixelIds / imageDimensions.x));
vec2 xy = pixel/imageDimensions;
float pixelValue = texture(tex2, xy).r;//Pick Pixel value from GPU texture ranges from 0-65535
float xDim = mod(pixelValue, 255.0)/256.0;
float yDim = floor(pixelValue / 255.0)/256.0;
float xVertex = (xDim*2.0) - 1.0;//convert 0.0 to 1.0 -> -1.0 -> 1.0, it will increment because we have used gl.blendFunc
float yVertex = 1.0 - (yDim*2.0);
gl_Position = vec4(xVertex, yVertex, 0.0, 1.0);
gl_PointSize = 1.0;
}
</script>
<script type="not-js" id="histogram-fs">
#version 300 es
precision mediump float;
out vec4 fcolor;
void main() {
fcolor = vec4(1.0, 1.0, 1.0, 1.0);
}
</script>
<script type="not-js" id="sorting-vs">
#version 300 es
in vec2 vertices;
void main () {
gl_Position = vec4(vertices, 0.0, 1.0);
}
</script>
<script type="not-js" id="sorting-fs">
#version 300 es
precision mediump float;
out vec4 fcolor;
uniform sampler2D tex3;
const int MAX_WIDTH = 65536;
void main() {
vec4 maxColor = vec4(0.0);
for (int i = 0; i < MAX_WIDTH; i++) {
float xDim = mod(float(i), 256.0)/256.0;
float yDim = floor(float(i) / 256.0)/256.0;
vec2 xy = vec2(xDim, yDim);
vec4 currPixel = texture(tex3, xy).rrra;
maxColor = max(maxColor, currPixel);
}
fcolor = vec4(maxColor);
}
</script>
<script type="not-js" id="showhistogram-vs">
#version 300 es
in vec2 vertices;
void main () {
gl_Position = vec4(vertices, 0.0, 1.0);
}
</script>
<script type="not-js" id="showhistogram-fs">
#version 300 es
precision mediump float;
uniform sampler2D histTex, maxTex;
uniform vec2 imageDimensions;
out vec4 fcolor;
void main () {
// get the max color constants
vec4 maxColor = texture(maxTex, vec2(0));
// compute our current UV position
vec2 uv = gl_FragCoord.xy / imageDimensions;
vec2 uv2 = gl_FragCoord.xy / vec2(256.0, 256.0);
// Get the history for this color
vec4 hist = texture(histTex, uv2);
// scale by maxColor so scaled goes from 0 to 1 with 1 = maxColor
vec4 scaled = hist / maxColor;
// 1 > maxColor, 0 otherwise
vec4 color = step(uv2.yyyy, scaled);
fcolor = vec4(color.rgb, 1);
}
</script>
<canvas id="canvas"></canvas>
<script type="text/javascript">
class WebGLUtils {
getGLContext = (canvas, version) => {
canvas.width = window.innerWidth * 0.99;
canvas.height = window.innerHeight * 0.85;
var gl = canvas.getContext(version ? 'webgl' : 'webgl2');
const ext = gl.getExtension("EXT_color_buffer_float");
if (!ext) {
console.log("sorry, can't render to floating point textures");
}
gl.clearColor(0, 0, 0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT|gl.DEPTH_BUFFER_BIT);
gl.lineWidth(0.5);
return gl;
};
clear = (gl) => {
gl.clear(gl.COLOR_BUFFER_BIT|gl.DEPTH_BUFFER_BIT);
};
getShader = (gl, type, shaderText) => {
var vfs = gl.createShader(type);
gl.shaderSource(vfs, shaderText);
gl.compileShader(vfs);
if (!gl.getShaderParameter(vfs, gl.COMPILE_STATUS)) {
console.error(gl.getShaderInfoLog(vfs));
}
return vfs;
};
getProgram = (gl, vertexShader, fragmentShader) => {
var program = gl.createProgram();
gl.attachShader(program, this.getShader(gl, gl.VERTEX_SHADER, document.getElementById(vertexShader).text.trim()));
gl.attachShader(program, this.getShader(gl, gl.FRAGMENT_SHADER, document.getElementById(fragmentShader).text.trim()));
gl.linkProgram(program);
if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
console.error(gl.getProgramInfoLog(program));
}
return program;
};
createAndBindBuffer = (gl, relatedVertices, isNotJSArray) => {
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, isNotJSArray ? relatedVertices : new Float32Array(relatedVertices), gl.STATIC_DRAW);
gl.bindBuffer(gl.ARRAY_BUFFER, null);
return buffer;
};
createAndBindTexture = (gl, _) => {
var texBuffer = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texBuffer);
if (_.img.width) {
gl.texImage2D(gl.TEXTURE_2D, 0, _.internalFormat, _.format, _.dataType, _.img);
} else {
gl.texImage2D(gl.TEXTURE_2D, 0, _.internalFormat, _.width, _.height, 0, _.format, _.dataType, _.img);
}
// set the filtering so we don't need mips
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, _.filter);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, _.filter);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, _.mipMapST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, _.mipMapST);
gl.bindTexture(gl.TEXTURE_2D, null);
return texBuffer;
};
createTextureAndFramebuffer = (gl, _) => {
const tex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texImage2D(gl.TEXTURE_2D, 0, _.internalFormat, _.width, _.height, 0, _.format, _.dataType, null);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, _.filter);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, _.filter);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, _.mipMapST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, _.mipMapST);
const fb = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
const status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
console.log(`can ${status === gl.FRAMEBUFFER_COMPLETE ? "" : "NOT "}render to R32`);
return {tex: tex, fb: fb};
};
linkAndSendDataToGPU = (gl, program, linkedVariable, buffer, dimensions) => {
var vertices = gl.getAttribLocation(program, linkedVariable);
gl.enableVertexAttribArray(vertices);
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.vertexAttribPointer(vertices, dimensions, gl.FLOAT, gl.FALSE, 0, 0);
return vertices;
};
sendDataToGPU = (gl, buffer, vertices, dimensions) => {
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.vertexAttribPointer(vertices, dimensions, gl.FLOAT, gl.FALSE, 0, 0);
};
sendTextureToGPU = (gl, tex, index) => {
gl.activeTexture(gl.TEXTURE0 + index);
gl.bindTexture(gl.TEXTURE_2D, tex);
};
calculateAspectRatio = (img, gl) => {
var cols = img.width;
var rows = img.height;
var imageAspectRatio = cols / rows;
var ele = gl.canvas;
var windowWidth = ele.width;
var windowHeight = ele.height;
var canvasAspectRatio = windowWidth / windowHeight;
var renderableHeight, renderableWidth;
var xStart, yStart;
/// If image's aspect ratio is less than canvas's we fit on height
/// and place the image centrally along width
if(imageAspectRatio < canvasAspectRatio) {
renderableHeight = windowHeight;
renderableWidth = cols * (renderableHeight / rows);
xStart = (windowWidth - renderableWidth) / 2;
yStart = 0;
}
/// If image's aspect ratio is greater than canvas's we fit on width
/// and place the image centrally along height
else if(imageAspectRatio > canvasAspectRatio) {
renderableWidth = windowWidth;
renderableHeight = rows * (renderableWidth / cols);
xStart = 0;
yStart = ( windowHeight - renderableHeight) / 2;
}
///keep aspect ratio
else {
renderableHeight = windowHeight ;
renderableWidth = windowWidth;
xStart = 0;
yStart = 0;
}
return {
y2 : yStart + renderableHeight,
x2 : xStart + renderableWidth,
x1 : xStart,
y1 : yStart
};
};
convertCanvasCoordsToGPUCoords = (canvas, AR) => {
//GPU -> -1, -1, 1, 1
//convert to 0 -> 1
var _0To1 = {
y2 : AR.y2/canvas.height,
x2 : AR.x2/canvas.width,
x1 : AR.x1/canvas.width,
y1 : AR.y1/canvas.height
};
//Convert -1 -> 1
return {
y2 : -1 + _0To1.y2 * 2.0,
x2 : -1 + _0To1.x2 * 2.0,
x1 : -1 + _0To1.x1 * 2.0,
y1 : -1 + _0To1.y1 * 2.0
};
};
//convert -1->+1 to 0.0->1.0
convertVertexToTexCoords = (x1, y1, x2, y2) => {
return {
y2 : (y2 + 1.0)/2.0,
x2 : (x2 + 1.0)/2.0,
x1 : (x1 + 1.0)/2.0,
y1 : (y1 + 1.0)/2.0
};
};
activateTextureByIndex = (gl, program, gpuRef, gpuTextureIndex) => {
gl.useProgram(program);
gl.uniform1i(gl.getUniformLocation(program, gpuRef), gpuTextureIndex);
};
prepareVec4 = (_) => {
return [_.x1, _.y1, 0.0, 1.0,
_.x2, _.y1, 0.0, 1.0,
_.x1, _.y2, 0.0, 1.0,
_.x2, _.y1, 0.0, 1.0,
_.x1, _.y2, 0.0, 1.0,
_.x2, _.y2, 0.0, 1.0];
};
prepareVec2 = (_) => {
return [_.x1, _.y1,
_.x2, _.y1,
_.x1, _.y2,
_.x2, _.y1,
_.x1, _.y2,
_.x2, _.y2];
};
};
</script>
I am able to render a 8 bit histogram in both WebGL1 and WebGL2 using this code. But I need to generate a 16 bit histogram using 16 bit texture.
Here's how am sending the texture to GPU:
var tex = gl.createTexture(); // create empty texture
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texImage2D(
gl.TEXTURE_2D, // target
0, // mip level
gl.RGBA16UI, // internal format -> gl.RGBA16UI
w, h, // width and height
0, // border
gl.RGBA_INTEGER, //format -> gl.RGBA_INTEGER
gl.UNSIGNED_SHORT, // type -> gl.UNSIGNED_SHORT
img // texture data
);
So, take the working example in mind, I am stuck with few things :
1) How to create a 65536 X 1 framebuffer/texture to keep the 16 bit histogram as WebGL clearly says : WebGL: INVALID_VALUE: texImage2D: width or height out of range. Can we try a 256 x 256 framebuffer? I tried but stuck in point no. 2 below.
2) How to read through the pixels inside the vertex shader in case of 16 bit, below code is for 8-bit data, will it work for 16 bit as well? As I can't debug, so can't say whether it works or not:
<script id="hist-vs" type="not-js">
attribute float pixelId;
uniform vec2 u_resolution;
uniform sampler2D u_texture;
uniform vec4 u_colorMult;
void main() {
// based on an id (0, 1, 2, 3 ...) compute the pixel x, y for the source image
vec2 pixel = vec2(mod(pixelId, u_resolution.x), floor(pixelId / u_resolution.x));
// compute corresponding uv center of that pixel
vec2 uv = (pixel + 0.5) / u_resolution;
// get the pixels but 0 out channels we don't want
vec4 color = texture2D(u_texture, uv) * u_colorMult;
// add up all the channels. Since 3 are zeroed out we'll get just one channel
float colorSum = color.r + color.g + color.b + color.a;
// set the position to be over a single pixel in the 256x1 destination texture
gl_Position = vec4((colorSum * 255.0 + 0.5) / 256.0 * 2.0 - 1.0, 0.5, 0, 1);
gl_PointSize = 1.0;
}
</script>
If you just want answers to your 2 questions then
1) How to create a 65536 X 1 framebuffer/texture to keep the 16 bit histogram as WebGL clearly says : WebGL: INVALID_VALUE: texImage2D: width or height out of range. Can we try a 256 x 256 framebuffer?
yes, you'd make 256x256 texture if you want to know the totals for each of the 65536 possible values
2) How to read through the pixels inside the vertex shader in case of 16 bit, below code is for 8-bit data, will it work for 16 bit as well? As I can't debug, so can't say whether it works or not:
Of course you can debug. You try it and see if the results are correct. If they aren't you look at your code and or the error messages and try to figure out why. That's called debugging. Make a 1x1 texture, call your function, check if the histogram has the correct count of 1 for that 1x1 pixel input by calling gl.readPixels. Then try 2x1 or 2x2.
In any case you can't read gl.RGBA16UI textures with GLSL 1.0 es. You have to use version 300 es so if you actually want to create a separate bucket for all 65536 values then
Here's some a WebGL2 GLSL 3.00 ES shader that will fill out the totals for values from 0 to 65535 in a 256x256 texture
#version 300 es
uniform usampler2D u_texture;
uniform uvec4 u_colorMult;
void main() {
const int mipLevel = 0;
ivec2 size = textureSize(u_texture, mipLevel);
// based on an id (0, 1, 2, 3 ...) compute the pixel x, y for the source image
vec2 pixel = vec2(
gl_VertexID % size.x,
gl_VertexID / size.x);
// get the pixels but 0 out channels we don't want
uvec4 color = texelFetch(u_texture, pixel, mipLevel) * u_colorMult;
// add up all the channels. Since 3 are zeroed out we'll get just one channel
uint colorSum = color.r + color.g + color.b + color.a;
vec2 outputPixel = vec2(
colorSum % 256u,
colorSum / 256u);
// set the position to be over a single pixel in the 256x256 destination texture
gl_Position = vec4((outputPixel + 0.5) / 256.0 * 2.0 - 1.0, 0, 1);
gl_PointSize = 1.0;
}
Example
Notes:
In WebGL2 you don't need pixelID, you can use gl_VertexID so no need to setup any buffers or attributes. Just call
const numPixels = img.width * img.height;
gl.drawArrays(gl.POINTS, 0, numPixels);
You can use textureSize to get the size of a texture so no need to pass it in.
You can use texelFetch to get a single texel(pixel) from a texture. It takes integer pixel coordinates.
To read an unsigned integer texture format like RGBA16UI you have to use a usampler2D otherwise you'll get an error at draw time drawing to use an RGBA16UI texture on a sampler2D (this is how I know you weren't actually using a RGBA16UI texture because you would have gotten an error in the JavaScript console telling you and leading you to change your shader.
You still need to use a floating point texture as the target because the technique used requires blending but blending doesn' work with integer textures (just in case you got the idea to try to use an integer based texture in the framebuffer)
I'm trying to read the pixels of greyscale heightmap in order to store the height values later in a mesh, but whatever I do, I constantly read the same values rgba(0, 0, 0, 255).
Note: Color normal images are perfectly read.
The image used:
Code I've written:
let canvas = document.querySelector("canvas");
let gl = canvas.getContext("webgl");
gl.canvas.width = canvas.getBoundingClientRect().width;
gl.canvas.height = canvas.getBoundingClientRect().height;
let vertexShaderSource = `
attribute vec4 a_position;
varying vec2 v_texturePos;
void main() {
gl_Position = vec4(a_position.xy, 0, 1.0);
v_texturePos = (a_position.xy+1.0)/2.0;
}
`;
let fragmentShaderSource = `
precision mediump float;
uniform sampler2D u_heightmap;
varying vec2 v_texturePos;
void main() {
gl_FragColor = texture2D(u_heightmap, v_texturePos);
}
`;
function createShader(gl, type, source) {
let shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
let success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
if(success)
return shader;
console.log(gl.getShaderInfoLog(shader));
gl.deleteShader(shader);
}
function createProgram(gl, vertexShader, fragmentShader) {
let program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
let success = gl.getProgramParameter(program, gl.LINK_STATUS);
if(success)
return program;
console.log(gl.getProgramInfoLog(program));
gl.deleteProgram(program);
}
let mesh = [
-1, -1, 0,
-1, 1, 0,
1, 1, 0,
1, 1, 0,
1, -1, 0,
-1, -1, 0
];
function drawScene(gl) {
gl.clearColor(0, 0, 0, 0);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(mesh), gl.STATIC_DRAW);
gl.vertexAttribPointer(attribPositionLoc, 3, gl.FLOAT, false, 0, 0);
gl.drawArrays(gl.TRIANGLES, 0, 6);
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) === gl.FRAMEBUFFER_COMPLETE) {
let pixels = new Uint8Array(gl.canvas.width*gl.canvas.height*4/625);
for(let g = 0; g < gl.canvas.width; g += 25) {
for(let h = 0; h < gl.canvas.height; h += 25) {
gl.readPixels(g, h, gl.canvas.width/25, gl.canvas.height/25, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
}
}
console.log(pixels);
}
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.bindTexture(gl.TEXTURE_2D, frameTexture);
gl.drawArrays(gl.TRIANGLES, 0, 6);
}
let attribPositionLoc;
let frameBuffer;
let texture, frameTexture;
function resize(gl) {
let realToCSSPixels = window.devicePixelRatio;
let displayWidth = Math.floor(gl.canvas.clientWidth * realToCSSPixels);
let displayHeight = Math.floor(gl.canvas.clientHeight * realToCSSPixels);
if (gl.canvas.width !== displayWidth ||
gl.canvas.height !== displayHeight) {
gl.canvas.width = displayWidth;
gl.canvas.height = displayHeight;
}
}
let img = document.createElement("img");
img.crossOrigin = "null";
img.src = "http://localhost:8000/heightmap?filename=terrain.jpg";
img.addEventListener("load", startWebGL.bind(this, gl));
function startWebGL(gl) {
resize(gl);
let vertexShader = createShader(gl, gl.VERTEX_SHADER, vertexShaderSource);
let fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, fragmentShaderSource);
let program = createProgram(gl, vertexShader, fragmentShader);
gl.useProgram(program);
gl.enable(gl.DEPTH_TEST);
gl.depthFunc(gl.LESS);
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
frameBuffer = gl.createFramebuffer();
frameTexture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, frameTexture);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
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.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.canvas.width, gl.canvas.height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
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_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, img);
gl.bindFramebuffer(gl.FRAMEBUFFER, frameBuffer);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, frameTexture, 0);
attribPositionLoc = gl.getAttribLocation(program, "a_position");
let positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
gl.enableVertexAttribArray(attribPositionLoc);
drawScene(gl);
}
<canvas></canvas>
What am I doing wrong and how can I fix it? Any ideas?
It's not at all clear what this code is trying to do
let pixels = new Uint8Array(gl.canvas.width*gl.canvas.height*4/625);
for(let g = 0; g < gl.canvas.width; g += 25) {
for(let h = 0; h < gl.canvas.height; h += 25) {
gl.readPixels(g, h, gl.canvas.width/25, gl.canvas.height/25, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
}
}
console.log(pixels);
What does dividing by 625 do? On top of that you only print the last result. If you want read the entire canvas it's just
let pixels = new Uint8Array(gl.canvas.width*gl.canvas.height*4);
gl.readPixels(g, h, gl.canvas.width, gl.canvas.height, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
In any case if I change the URL for the image to something that can be loaded while on stack overflow I see the expected values. Looking at your image since you're only reading at 25x25 area and you're only printing the last 25x25 area since your console.log is outside the loop I'm guessing your reading a black corner of the image.
Also since you're stepping by 25, if your canvas is not a multiple of 25 then you'll read off the edge, past the end of the canvas. Reading off the edge always produces 0,0,0,0.
let canvas = document.querySelector("canvas");
let gl = canvas.getContext("webgl");
gl.canvas.width = canvas.getBoundingClientRect().width;
gl.canvas.height = canvas.getBoundingClientRect().height;
let vertexShaderSource = `
attribute vec4 a_position;
varying vec2 v_texturePos;
void main() {
gl_Position = vec4(a_position.xy, 0, 1.0);
v_texturePos = (a_position.xy+1.0)/2.0;
}
`;
let fragmentShaderSource = `
precision mediump float;
uniform sampler2D u_heightmap;
varying vec2 v_texturePos;
void main() {
gl_FragColor = texture2D(u_heightmap, v_texturePos);
}
`;
function createShader(gl, type, source) {
let shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
let success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
if(success)
return shader;
console.log(gl.getShaderInfoLog(shader));
gl.deleteShader(shader);
}
function createProgram(gl, vertexShader, fragmentShader) {
let program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
let success = gl.getProgramParameter(program, gl.LINK_STATUS);
if(success)
return program;
console.log(gl.getProgramInfoLog(program));
gl.deleteProgram(program);
}
let mesh = [
-1, -1, 0,
-1, 1, 0,
1, 1, 0,
1, 1, 0,
1, -1, 0,
-1, -1, 0
];
function drawScene(gl) {
gl.clearColor(0, 0, 0, 0);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(mesh), gl.STATIC_DRAW);
gl.vertexAttribPointer(attribPositionLoc, 3, gl.FLOAT, false, 0, 0);
gl.drawArrays(gl.TRIANGLES, 0, 6);
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) === gl.FRAMEBUFFER_COMPLETE) {
let pixels = new Uint8Array(gl.canvas.width*gl.canvas.height*4/625);
for(let g = 0; g < gl.canvas.width; g += 25) {
for(let h = 0; h < gl.canvas.height; h += 25) {
gl.readPixels(g, h, gl.canvas.width/25, gl.canvas.height/25, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
}
}
console.log(pixels);
}
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.bindTexture(gl.TEXTURE_2D, frameTexture);
gl.drawArrays(gl.TRIANGLES, 0, 6);
}
let attribPositionLoc;
let frameBuffer;
let texture, frameTexture;
function resize(gl) {
let realToCSSPixels = window.devicePixelRatio;
let displayWidth = Math.floor(gl.canvas.clientWidth * realToCSSPixels);
let displayHeight = Math.floor(gl.canvas.clientHeight * realToCSSPixels);
if (gl.canvas.width !== displayWidth ||
gl.canvas.height !== displayHeight) {
gl.canvas.width = displayWidth;
gl.canvas.height = displayHeight;
}
}
let img = document.createElement("img");
img.crossOrigin = "null";
// img.src = "http://localhost:8000/heightmap?filename=terrain.jpg";
img.src = "https://i.imgur.com/ZKMnXce.png";
img.addEventListener("load", startWebGL.bind(this, gl));
function startWebGL(gl) {
resize(gl);
let vertexShader = createShader(gl, gl.VERTEX_SHADER, vertexShaderSource);
let fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, fragmentShaderSource);
let program = createProgram(gl, vertexShader, fragmentShader);
gl.useProgram(program);
gl.enable(gl.DEPTH_TEST);
gl.depthFunc(gl.LESS);
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
frameBuffer = gl.createFramebuffer();
frameTexture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, frameTexture);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
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.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.canvas.width, gl.canvas.height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
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_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, img);
gl.bindFramebuffer(gl.FRAMEBUFFER, frameBuffer);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, frameTexture, 0);
attribPositionLoc = gl.getAttribLocation(program, "a_position");
let positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
gl.enableVertexAttribArray(attribPositionLoc);
drawScene(gl);
}
<canvas></canvas>
I am currently trying to render a simple texture with WebGL.
This is basically a port from normal system OpenGL.
It doesn't seem to work and I seriously have no idea what's wrong as it also seems very difficult to debug these thing.
I am getting an error on Firefox though:
"Error: WebGL: drawElements: Drawing to a destination rect smaller than the viewport rect. (This warning will only be given once)"
The viewport / projection matrix / positions seem to be correct so why am I getting that error?
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Test</title>
<style>
.canstyle {
width: 800px;
height: 600px;
}
</style>
</head>
<body>
<canvas id="canvas0" class="canstyle">
</canvas>
<script type='text/javascript'>
var vertexShaderSrc = `
precision mediump float;
attribute vec2 aVertexPosition;
attribute vec2 aTextureCoord;
uniform mat3 projectionMatrix;
varying vec2 vTextureCoord;
void main() {
gl_Position = vec4((projectionMatrix * vec3(aVertexPosition, 1.0)).xy, 0.0, 1.0);
vTextureCoord = aTextureCoord;
}
`;
var fragmentShaderSrc = `
precision mediump float;
varying vec2 vTextureCoord;
uniform sampler2D uSampler;
void main() {
gl_FragColor = texture2D(uSampler, vTextureCoord);
}
`;
var img1 = new Image(); // HTML5 Constructor
img1.src = 'bunny.png';
img1.alt = 'alt';
img1.onload = function() {
render();
}
function render() {
var canvas = document.getElementById("canvas0");
var gl = canvas.getContext("webgl", {
alpha: false,
depth: false,
stencil: true,
premultipliedAlpha: false
});
var funcs = Object.getOwnPropertyNames(gl.__proto__).filter(function(p) {
return typeof gl[p] === 'function';
});
function HookFunction(func, callback) {
return function() {
var res = func.apply(this, arguments);
callback(arguments);
return res;
};
}
var endFrame = false;
var afterFrame = 8;
funcs.forEach(function(funcName) {
gl[funcName] = HookFunction(gl[funcName], function(args) {
if (endFrame) {
if (afterFrame == 0) {
return;
}
afterFrame -= 1;
}
if (funcName == "drawElements") {
endFrame = true;
}
var KK = [];
var dumpArr = [];
for (var item in args) {
var arg = args[item];
if (arg === null) {
KK.push("null");
} else if (arg instanceof ArrayBuffer || arg instanceof Float32Array || arg instanceof Uint8Array || arg instanceof Uint16Array) {
dumpArr.push(new Uint8Array(arg.buffer));
} else {
KK.push(arg);
}
}
console.log("WebGL Interceptor: ", funcName, "(", KK.join(', '), ")");
if (dumpArr.length) {
console.log(dumpArr);
}
});
});
gl.disable(gl.DEPTH_TEST);
gl.disable(gl.CULL_FACE);
gl.disable(gl.STENCIL_TEST);
gl.enable(gl.BLEND);
gl.enable(gl.SCISSOR_TEST);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.viewport(0, 0, 800, 600);
gl.scissor(0, 0, 800, 600);
gl.clearColor(0.06274509803921569, 0.6, 0.7333333333333333, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
var vertexDataCount = 4;
var vertexByteSize = vertexDataCount * 4;
var BatchSize = 2000;
var totalIndices = BatchSize * 6;
var vertices = new ArrayBuffer(BatchSize * vertexByteSize * 4);
var indices = new ArrayBuffer(totalIndices * 2);
var indicesUint16View = new Uint16Array(indices);
var verticesFloat32View = new Float32Array(vertices);
var j = 0;
for (var i = 0; i < totalIndices; i += 6, j += 4) {
indicesUint16View[i + 0] = j + 0;
indicesUint16View[i + 1] = j + 1;
indicesUint16View[i + 2] = j + 2;
indicesUint16View[i + 3] = j + 0;
indicesUint16View[i + 4] = j + 2;
indicesUint16View[i + 5] = j + 3;
}
var indexBuffer = gl.createBuffer();
var vertexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indicesUint16View, gl.STATIC_DRAW);
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
gl.bufferData(gl.ARRAY_BUFFER, verticesFloat32View, gl.DYNAMIC_DRAW);
function compileShader(shaderSource, shaderType) {
var shader = gl.createShader(shaderType);
gl.shaderSource(shader, shaderSource);
gl.compileShader(shader);
var success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
if (!success) {
throw "could not compile shader:" + gl.getShaderInfoLog(shader);
}
return shader;
}
function createProgram(vertexShader, fragmentShader) {
var program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
var success = gl.getProgramParameter(program, gl.LINK_STATUS);
if (!success) {
throw ("program filed to link:" + gl.getProgramInfoLog(program));
}
return program;
}
var vertexShad = compileShader(vertexShaderSrc, gl.VERTEX_SHADER);
var fragShad = compileShader(fragmentShaderSrc, gl.FRAGMENT_SHADER);
var shaderProg = createProgram(vertexShad, fragShad);
gl.useProgram(shaderProg);
var vertLoc = gl.getAttribLocation(shaderProg, "aVertexPosition");
var texCoordLoc = gl.getAttribLocation(shaderProg, "aTextureCoord");
gl.enableVertexAttribArray(vertLoc);
gl.enableVertexAttribArray(texCoordLoc);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
gl.vertexAttribPointer(vertLoc, 2, gl.FLOAT, false, vertexByteSize, 0);
gl.vertexAttribPointer(texCoordLoc, 2, gl.FLOAT, false, vertexByteSize, 2 * 4);
var currIndex = 0;
verticesFloat32View[currIndex++] = 174; // pos
verticesFloat32View[currIndex++] = 113; // pos
verticesFloat32View[currIndex++] = 0; // UV
verticesFloat32View[currIndex++] = 0; // UV
verticesFloat32View[currIndex++] = 226; // pos
verticesFloat32View[currIndex++] = 113; // pos
verticesFloat32View[currIndex++] = 1; // UV
verticesFloat32View[currIndex++] = 0; // UV
verticesFloat32View[currIndex++] = 226; // pos
verticesFloat32View[currIndex++] = 187; // pos
verticesFloat32View[currIndex++] = 1; // UV
verticesFloat32View[currIndex++] = 1; // UV
verticesFloat32View[currIndex++] = 174; // pos
verticesFloat32View[currIndex++] = 187; // pos
verticesFloat32View[currIndex++] = 0; // UV
verticesFloat32View[currIndex++] = 1; // UV
gl.bufferSubData(gl.ARRAY_BUFFER, 0, verticesFloat32View);
// | 2 / Width | 0 | -1
// | 0 | 2 / Height | -1
// | 0 | 0 | 1
var rawProjectionMat = new Float32Array([
0.00249999994, 0, 0, 0, -0.00333333341, 0, -1, 1, 1
]);
gl.uniformMatrix3fv(gl.getUniformLocation(shaderProg, "projectionMatrix"), false, rawProjectionMat);
gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
gl.activeTexture(gl.TEXTURE0);
var texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
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.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, true);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, img1);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
}
</script>
</body>
</html>
EDIT:
I am using the following image:
https://raw.githubusercontent.com/pixijs/examples/gh-pages/_assets/bunny.png
I'm just guessing the issue is no where did you set the size of your canvas element's content.
The number of actual pixels in the canvas element defaults to 300x150. you can set that in HTML with
<canvas width="800" height="600"></canvas>
or you can set it in JavaScript with
someCanvasElement.width = 800;
someCanvasElement.height = 600;
Firefox is warning you that you set the viewport to 800x600 but it's larger than your canvas (300x150) which is very unusual and the warning was to help you notice the issue.
FYI: gl.viewport only does 2 things. It sets the conversion from clip space to screen space (or in this case canvas space) and it sets the clipping region for vertices. 'clipping vertices' means it does not clip pixels so drawing a gl_PointSize = 10.0 point at the edge of the viewport setting will draw outside the viewport setting.
To clip pixels use the scissor test. I see you're setting up a scissor test but since you apparently want to draw to the edge of the canvas you don't need to setup the scissor at all.