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webgl-canvas-clientwidth-clientheight.html
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<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL - projection using clientWidth, clientHeight</title>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
<style>
body {
margin: 0px;
}
canvas {
display: block;
width: 100vw;
height: 100vh;
border: 0px !important;
}
h1 {
position: absolute;
left: 10px;
}
.description {
position: absolute;
left: 10px;
bottom: 10px;
text-shadow:
-1px -1px 0 #FFF,
1px -1px 0 #FFF,
-1px 1px 0 #FFF,
1px 1px 0 #FFF;
}
.iframe .description {
display: none;
}
</style>
</head>
<body>
<canvas id="canvas" width="400" height="300"></canvas>
<div class="description">resize this window tall and thin or short and wide.<br/> Notice the F keeps the correct aspect</div>
</body>
<!-- vertex shader -->
<script id="vertex-shader-2d" type="x-shader/x-vertex">
attribute vec2 a_position;
uniform mat3 u_matrix;
void main() {
// Multiply the position by the matrix.
gl_Position = vec4((u_matrix * vec3(a_position, 1)).xy, 0, 1);
}
</script>
<!-- fragment shader -->
<script id="fragment-shader-2d" type="x-shader/x-fragment">
precision mediump float;
uniform vec4 u_color;
void main() {
gl_FragColor = u_color;
}
</script>
<!-- this is here to hide description in iframe. Feel free to remove it -->
<script src="resources/lessons-helper.js"></script>
<!--
for most samples webgl-utils only provides shader compiling/linking and
canvas resizing because why clutter the examples with code that's the same in every sample.
See https://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and https://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<script src="resources/webgl-utils.js"></script>
<script src="resources/m3.js"></script>
<script>
"use strict";
function main() {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
var canvas = document.querySelector("#canvas");
var gl = canvas.getContext("webgl");
if (!gl) {
return;
}
// setup GLSL program
var program = webglUtils.createProgramFromScripts(gl, ["vertex-shader-2d", "fragment-shader-2d"]);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
// lookup uniforms
var colorLocation = gl.getUniformLocation(program, "u_color");
var matrixLocation = gl.getUniformLocation(program, "u_matrix");
// Create a buffer to put positions in
var positionBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Put geometry data into buffer
setGeometry(gl);
var translation = [30, 10];
var angleInRadians = 0;
var scale = [1, 1];
var color = [Math.random(), Math.random(), Math.random(), 1];
drawScene();
// Draw the scene.
function drawScene() {
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// Clear the canvas.
gl.clear(gl.COLOR_BUFFER_BIT);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// Turn on the attribute
gl.enableVertexAttribArray(positionLocation);
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation, size, type, normalize, stride, offset);
// set the color
gl.uniform4fv(colorLocation, color);
// Compute the matrices
var matrix = m3.projection(gl.canvas.clientWidth, gl.canvas.clientHeight);
matrix = m3.translate(matrix, translation[0], translation[1]);
matrix = m3.rotate(matrix, angleInRadians);
matrix = m3.scale(matrix, scale[0], scale[1]);
// Set the matrix.
gl.uniformMatrix3fv(matrixLocation, false, matrix);
// Draw the geometry.
var primitiveType = gl.TRIANGLES;
var offset = 0;
var count = 18; // 6 triangles in the 'F', 3 points per triangle
gl.drawArrays(primitiveType, offset, count);
}
window.addEventListener('resize', drawScene, false);
}
// Fill the buffer with the values that define a letter 'F'.
function setGeometry(gl) {
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array([
// left column
0, 0,
30, 0,
0, 150,
0, 150,
30, 0,
30, 150,
// top rung
30, 0,
100, 0,
30, 30,
30, 30,
100, 0,
100, 30,
// middle rung
30, 60,
67, 60,
30, 90,
30, 90,
67, 60,
67, 90,
]),
gl.STATIC_DRAW);
}
main();
</script>
</html>