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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>
</head>
<body>
<canvas id="canvas" width="128" height="128"></canvas>
<script id="shader-fs" type="x-shader/x-fragment">
precision mediump float;
uniform vec4 mtrColor;
void main(void) {
gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0) * mtrColor;
}
</script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec3 aVertexPosition;
void main(void) {
gl_PointSize = 5.0;
gl_Position = vec4(aVertexPosition, 1.0);
}
</script>
<script type="text/javascript;version=1.8">
"use strict";
let canvas, gl, shaderProgram;
let triangleVertexPositionBuffer, squareVertexPositionBuffer;
window.onload = function() {
canvas = document.querySelector("canvas");
gl = canvas.getContext("webgl", { preserveDrawingBuffer: true });
gl.viewportWidth = canvas.width;
gl.viewportHeight = canvas.height;
initShaders();
initBuffers();
gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.disable(gl.DEPTH_TEST);
drawScene();
}
function getShader(gl, id) {
var shaderScript = document.getElementById(id);
if (!shaderScript) {
return null;
}
var str = "";
var k = shaderScript.firstChild;
while (k) {
if (k.nodeType == 3) {
str += k.textContent;
}
k = k.nextSibling;
}
var shader;
if (shaderScript.type == "x-shader/x-fragment") {
shader = gl.createShader(gl.FRAGMENT_SHADER);
} else if (shaderScript.type == "x-shader/x-vertex") {
shader = gl.createShader(gl.VERTEX_SHADER);
} else {
return null;
}
gl.shaderSource(shader, str);
gl.compileShader(shader);
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
alert(gl.getShaderInfoLog(shader));
return null;
}
return shader;
}
function initShaders() {
var fragmentShader = getShader(gl, "shader-fs");
var vertexShader = getShader(gl, "shader-vs");
shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertexShader);
gl.attachShader(shaderProgram, fragmentShader);
gl.linkProgram(shaderProgram);
if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
alert("Could not initialise shaders");
}
gl.useProgram(shaderProgram);
shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
shaderProgram.pMaterialColor = gl.getUniformLocation(shaderProgram, "mtrColor");
gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);
}
function initBuffers() {
// Create triangle vertex/index buffer
triangleVertexPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
var vertices = [
0.0, 0.5, 0.0,
-0.5, -0.5, 0.0,
0.5, -0.5, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
triangleVertexPositionBuffer.itemSize = 3;
triangleVertexPositionBuffer.numItems = 3;
// Create square vertex/index buffer
squareVertexPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
vertices = [
0.8, 0.8, 0.0,
-0.8, 0.8, 0.0,
0.8, -0.8, 0.0,
-0.8, -0.8, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
squareVertexPositionBuffer.itemSize = 3;
squareVertexPositionBuffer.numItems = 4;
}
function drawScene() {
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);
// DrawArrays
// --------------
// draw square - triangle strip
gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.uniform4f(shaderProgram.pMaterialColor, 1, 1, 1, 1);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, squareVertexPositionBuffer.numItems);
// draw square - triangle fan
gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.uniform4f(shaderProgram.pMaterialColor, 0, 1, 0, 1);
gl.drawArrays(gl.TRIANGLE_FAN, 0, squareVertexPositionBuffer.numItems);
// draw triangle
gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, triangleVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.uniform4f(shaderProgram.pMaterialColor, 1, 0, 0, 1);
gl.drawArrays(gl.TRIANGLES, 0, triangleVertexPositionBuffer.numItems);
// draw points
gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.uniform4f(shaderProgram.pMaterialColor, 1, 0, 1, 1);
gl.drawArrays(gl.POINTS, 0, squareVertexPositionBuffer.numItems);
// draw lines
gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.uniform4f(shaderProgram.pMaterialColor, 0, 0, 1, 1);
gl.lineWidth(8.0);
gl.drawArrays(gl.LINES, 0, squareVertexPositionBuffer.numItems);
// draw line strip
gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.uniform4f(shaderProgram.pMaterialColor, 0.9, 0.6, 0, 1);
gl.lineWidth(3.0);
gl.drawArrays(gl.LINE_STRIP, 0, squareVertexPositionBuffer.numItems);
// draw line loop
gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, triangleVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.uniform4f(shaderProgram.pMaterialColor, 0, 1, 1, 1);
gl.lineWidth(3.0);
gl.drawArrays(gl.LINE_LOOP, 0, triangleVertexPositionBuffer.numItems);
window.requestAnimationFrame(drawScene);
}
</script>
</body>
</html>
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