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<!-- Any copyright is dedicated to the Public Domain.
http://creativecommons.org/publicdomain/zero/1.0/ -->
<!doctype html>
<html>
<head>
<meta charset="utf-8"/>
<title>WebGL editor test page</title>
<script id="shader-vs" type="x-shader/x-vertex">
precision lowp float;
attribute vec3 aVertexPosition;
attribute vec3 aVertexColor;
varying vec3 vFragmentColor;
void main(void) {
gl_Position = vec4(aVertexPosition, 1.0);
vFragmentColor = aVertexColor; // I'm special!
}
</script>
<script id="shader-fs" type="x-shader/x-fragment">
precision lowp float;
varying vec3 vFragmentColor;
void main(void) {
gl_FragColor = vec4(vFragmentColor, 1.0); // I'm also special!
}
</script>
</head>
<body>
<canvas width="512" height="512"></canvas>
<script type="text/javascript;version=1.8">
"use strict";
let canvas, gl;
let program;
let squareVerticesPositionBuffer;
let squareVerticesColorBuffer;
let vertexPositionAttribute;
let vertexColorAttribute;
window.onload = function() {
canvas = document.querySelector("canvas");
gl = canvas.getContext("webgl", { preserveDrawingBuffer: true });
gl.clearColor(0.0, 0.0, 0.0, 1.0);
initProgram();
initBuffers();
drawScene();
}
function initProgram() {
let vertexShader = getShader(gl, "shader-vs");
let fragmentShader = getShader(gl, "shader-fs");
program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
vertexPositionAttribute = gl.getAttribLocation(program, "aVertexPosition");
gl.enableVertexAttribArray(vertexPositionAttribute);
vertexColorAttribute = gl.getAttribLocation(program, "aVertexColor");
gl.enableVertexAttribArray(vertexColorAttribute);
}
function getShader(gl, id) {
let script = document.getElementById(id);
let source = script.textContent;
let shader;
if (script.type == "x-shader/x-fragment") {
shader = gl.createShader(gl.FRAGMENT_SHADER);
} else if (script.type == "x-shader/x-vertex") {
shader = gl.createShader(gl.VERTEX_SHADER);
}
gl.shaderSource(shader, source);
gl.compileShader(shader);
return shader;
}
function initBuffers() {
squareVerticesPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, squareVerticesPositionBuffer);
gl.bufferData(gl.ARRAY_BUFFER, 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
]), gl.STATIC_DRAW);
squareVerticesColorBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, squareVerticesColorBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
1.0, 1.0, 1.0, 1.0,
1.0, 0.0, 0.0, 1.0,
0.0, 1.0, 0.0, 1.0,
0.0, 0.0, 1.0, 1.0
]), gl.STATIC_DRAW);
}
function drawScene() {
gl.clear(gl.COLOR_BUFFER_BIT);
gl.bindBuffer(gl.ARRAY_BUFFER, squareVerticesPositionBuffer);
gl.vertexAttribPointer(vertexPositionAttribute, 3, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, squareVerticesColorBuffer);
gl.vertexAttribPointer(vertexColorAttribute, 4, gl.FLOAT, false, 0, 0);
gl.useProgram(program);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
window.requestAnimationFrame(drawScene);
}
</script>
</body>
</html>
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