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image.html
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<!-- vim: sw=4 ts=4 expandtab smartindent ft=javascript
-->
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>WebGL Demo</title>
<style> document, body { margin: 0px; padding: 0px; overflow: hidden; } </style>
</head>
<body>
<canvas id="glcanvas"></canvas>
<script>
const canvas = document.getElementById('glcanvas');
const gl = canvas.getContext('webgl2', {antialias: true});
if (!gl) { alert('Failed to initialize WebGL'); }
(window.onresize = () => {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
/* account for e.g. high-retina macbook screens */
if (window.devicePixelRatio > 1) {
canvas.style.width = `${canvas.width}px`;
canvas.style.height = `${canvas.height}px`;
canvas.width *= window.devicePixelRatio;
canvas.height *= window.devicePixelRatio;
}
gl.viewport(
0,
0,
canvas.width,
canvas.height
);
})();
const geo_vbuf_pos = gl.createBuffer();
const geo_vbuf_uv = gl.createBuffer();
const geo_ibuf = gl.createBuffer();
let shaders;
/* compile shaders */
{
const vs_geo = `
attribute vec3 a_pos;
attribute vec2 a_uv;
varying vec2 v_uv;
void main() {
gl_Position = vec4(a_pos.xyz, 1);
v_uv = a_uv;
}`;
const fs_geo = `
precision mediump float;
uniform sampler2D u_texture;
varying vec2 v_uv;
void main() {
gl_FragColor = texture2D(u_texture, v_uv);
}`;
function createProgram(gl, vertexSource, fragmentSource) {
function createShader(gl, type, source) {
const shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
throw new Error(gl.getShaderInfoLog(shader));
}
return shader;
}
const program = gl.createProgram();
const vertexShader = createShader(gl, gl.VERTEX_SHADER, vertexSource);
const fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, fragmentSource);
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
throw new Error(gl.getProgramInfoLog(program));
}
const wrapper = {program};
const numAttributes = gl.getProgramParameter(program, gl.ACTIVE_ATTRIBUTES);
for (let i = 0; i < numAttributes; i++) {
const attribute = gl.getActiveAttrib(program, i);
wrapper[attribute.name] = gl.getAttribLocation(program, attribute.name);
}
const numUniforms = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS);
for (let i = 0; i < numUniforms; i++) {
const uniform = gl.getActiveUniform(program, i);
wrapper[uniform.name] = gl.getUniformLocation(program, uniform.name);
}
return wrapper;
}
shaders = {
geo: createProgram(gl, vs_geo, fs_geo)
}
}
let atlas = gl.createTexture();
{
const canvas = document.createElement("canvas");
const SIZE = canvas.width = canvas.height = 500;
const ctx = canvas.getContext("2d");
const PAD = SIZE*0.05;
ctx.font = (SIZE - PAD*2) + 'px sans-serif';
ctx.fillText('🤨', PAD, SIZE - PAD*2);
gl.bindTexture(gl.TEXTURE_2D, atlas);
gl.texImage2D(
/* target */ gl.TEXTURE_2D,
/* level */ 0,
/* internalformat */ gl.RGBA,
/* width */ canvas.width,
/* height */ canvas.height,
/* border, */ 0,
/* format, */ gl.RGBA,
/* type, */ gl.UNSIGNED_BYTE,
/* data */ canvas
);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
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);
}
requestAnimationFrame(function frame(timestamp) {
requestAnimationFrame(frame);
const geo_idx = [];
const geo_pos = [];
const geo_uv = [];
{
geo_uv.push(
1, 1,
0, 1,
0, 0,
1, 0,
);
const vbuf_i = geo_pos.length / 3;
geo_pos.push( 0.4, -0.4, 0.1);
geo_pos.push(-0.4, -0.4, 0.1);
geo_pos.push(-0.4, 0.4, 0.1);
geo_pos.push( 0.4, 0.4, 0.1);
geo_idx.push(0, 1, 2, 2, 3, 0);
}
{
/* set up premultiplied alpha */
gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
gl.enable(gl.BLEND);
gl.enable(gl.DEPTH_TEST);
gl.depthFunc(gl.LEQUAL);
/* clear all */
gl.clearColor(1, 1, 1, 1);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
/* geo pass */
{
gl.useProgram(shaders.geo.program);
gl.enableVertexAttribArray(shaders.geo.a_pos);
gl.enableVertexAttribArray(shaders.geo.a_uv);
/* upload/bind atlas */
{
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, atlas);
gl.uniform1i(shaders.geo.u_texture, 0);
}
/* upload/bind geometry */
{
gl.bindBuffer(gl.ARRAY_BUFFER, geo_vbuf_pos);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(geo_pos), gl.STATIC_DRAW);
gl.vertexAttribPointer(shaders.geo.a_pos, 3, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, geo_vbuf_uv);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(geo_uv), gl.STATIC_DRAW);
gl.vertexAttribPointer(shaders.geo.a_uv, 2, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, geo_ibuf);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(geo_idx), gl.STATIC_DRAW);
}
gl.drawElements(gl.TRIANGLES, geo_idx.length, gl.UNSIGNED_SHORT, 0);
}
}
})
</script>
</body>
</html>