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webgl-text-html-canvas2d.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 Text - HTML Canvas2D</title>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
<style>
* {
box-sizing: border-box;
}
#ui {
width: 200px;
}
.container {
position: relative;
}
#text {
background-color: transparent; /* needed because webgl-tutoraisl.css sets canvas bg color to white */
position: absolute;
left: 0px;
top: 0px;
z-index: 10;
}
</style>
<!--
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/m4.js"></script>
</head>
<body>
<div class="description">
HTML Text Canvas2D
</div>
<div class="container">
<canvas id="canvas"></canvas>
<canvas id="text"></canvas>
</div>
</body>
<!-- vertex shader -->
<script id="vertex-shader-3d" type="x-shader/x-vertex">
attribute vec4 a_position;
attribute vec4 a_color;
uniform mat4 u_matrix;
varying vec4 v_color;
void main() {
// Multiply the position by the matrix.
gl_Position = u_matrix * a_position;
// Pass the color to the fragment shader.
v_color = a_color;
}
</script>
<!-- fragment shader -->
<script id="fragment-shader-3d" type="x-shader/x-fragment">
precision mediump float;
// Passed in from the vertex shader.
varying vec4 v_color;
void main() {
gl_FragColor = v_color;
}
</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;
}
// look up the text canvas.
var textCanvas = document.querySelector("#text");
// make a 2D context for it
var ctx = textCanvas.getContext("2d");
// setup GLSL program
var program = webglUtils.createProgramFromScripts(gl, ["vertex-shader-3d", "fragment-shader-3d"]);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
var colorLocation = gl.getAttribLocation(program, "a_color");
// lookup uniforms
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);
// Create a buffer to put colors in
var colorBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = colorBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);
// Put geometry data into buffer
setColors(gl);
function radToDeg(r) {
return r * 180 / Math.PI;
}
function degToRad(d) {
return d * Math.PI / 180;
}
var translation = [0, 30, -360];
var rotation = [degToRad(190), degToRad(0), degToRad(0)];
var scale = [1, 1, 1];
var fieldOfViewRadians = degToRad(60);
var rotationSpeed = 1.2;
var then = 0;
requestAnimationFrame(drawScene);
// Draw the scene.
function drawScene(clock) {
// Convert to seconds
clock *= 0.001;
// Subtract the previous time from the current time
var deltaTime = clock - then;
// Remember the current time for the next frame.
then = clock;
// Every frame increase the rotation a little.
rotation[1] += rotationSpeed * deltaTime;
rotation[2] += deltaTime;
webglUtils.resizeCanvasToDisplaySize(gl.canvas);
webglUtils.resizeCanvasToDisplaySize(ctx.canvas);
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// Clear the canvas AND the depth buffer.
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Clear the 2D canvas
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
// Turn on culling. By default backfacing triangles
// will be culled.
gl.enable(gl.CULL_FACE);
// Enable the depth buffer
gl.enable(gl.DEPTH_TEST);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// Turn on the position attribute
gl.enableVertexAttribArray(positionLocation);
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 3; // 3 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);
// Turn on the color attribute
gl.enableVertexAttribArray(colorLocation);
// Bind the color buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);
// Tell the attribute how to get data out of colorBuffer (ARRAY_BUFFER)
var size = 3; // 3 components per iteration
var type = gl.UNSIGNED_BYTE; // the data is 8bit unsigned values
var normalize = true; // normalize the data (convert from 0-255 to 0-1)
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(
colorLocation, size, type, normalize, stride, offset);
// Compute the matrices
var aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
var projectionMatrix =
m4.perspective(fieldOfViewRadians, aspect, 1, 2000);
var spread = 170;
for (var yy = -1; yy <= 1; ++yy) {
for (var xx = -2; xx <= 2; ++xx) {
var matrix = m4.translate(projectionMatrix,
translation[0] + xx * spread, translation[1] + yy * spread, translation[2]);
matrix = m4.xRotate(matrix, rotation[0]);
matrix = m4.yRotate(matrix, rotation[1] + yy * xx * 0.2);
matrix = m4.zRotate(matrix, rotation[2] + (yy * 3 + xx) * 0.1);
matrix = m4.translate(matrix, -50, -75, 0);
// Set the matrix.
gl.uniformMatrix4fv(matrixLocation, false, matrix);
// Draw the geometry.
gl.drawArrays(gl.TRIANGLES, 0, 16 * 6);
// compute a clipspace position
// using the matrix we computed for the F
var clipspace = m4.transformVector(matrix, [100, 0, 0, 1]);
// divide X and Y by W just like the GPU does.
clipspace[0] /= clipspace[3];
clipspace[1] /= clipspace[3];
// convert from clipspace to pixels
var pixelX = (clipspace[0] * 0.5 + 0.5) * gl.canvas.width;
var pixelY = (clipspace[1] * -0.5 + 0.5) * gl.canvas.height;
ctx.fillText("" + xx + "," + yy, pixelX, pixelY);
}
}
requestAnimationFrame(drawScene);
}
}
// Fill the buffer with the values that define a letter 'F'.
function setGeometry(gl) {
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array([
// left column front
0, 0, 0,
0, 150, 0,
30, 0, 0,
0, 150, 0,
30, 150, 0,
30, 0, 0,
// top rung front
30, 0, 0,
30, 30, 0,
100, 0, 0,
30, 30, 0,
100, 30, 0,
100, 0, 0,
// middle rung front
30, 60, 0,
30, 90, 0,
67, 60, 0,
30, 90, 0,
67, 90, 0,
67, 60, 0,
// left column back
0, 0, 30,
30, 0, 30,
0, 150, 30,
0, 150, 30,
30, 0, 30,
30, 150, 30,
// top rung back
30, 0, 30,
100, 0, 30,
30, 30, 30,
30, 30, 30,
100, 0, 30,
100, 30, 30,
// middle rung back
30, 60, 30,
67, 60, 30,
30, 90, 30,
30, 90, 30,
67, 60, 30,
67, 90, 30,
// top
0, 0, 0,
100, 0, 0,
100, 0, 30,
0, 0, 0,
100, 0, 30,
0, 0, 30,
// top rung right
100, 0, 0,
100, 30, 0,
100, 30, 30,
100, 0, 0,
100, 30, 30,
100, 0, 30,
// under top rung
30, 30, 0,
30, 30, 30,
100, 30, 30,
30, 30, 0,
100, 30, 30,
100, 30, 0,
// between top rung and middle
30, 30, 0,
30, 60, 30,
30, 30, 30,
30, 30, 0,
30, 60, 0,
30, 60, 30,
// top of middle rung
30, 60, 0,
67, 60, 30,
30, 60, 30,
30, 60, 0,
67, 60, 0,
67, 60, 30,
// right of middle rung
67, 60, 0,
67, 90, 30,
67, 60, 30,
67, 60, 0,
67, 90, 0,
67, 90, 30,
// bottom of middle rung.
30, 90, 0,
30, 90, 30,
67, 90, 30,
30, 90, 0,
67, 90, 30,
67, 90, 0,
// right of bottom
30, 90, 0,
30, 150, 30,
30, 90, 30,
30, 90, 0,
30, 150, 0,
30, 150, 30,
// bottom
0, 150, 0,
0, 150, 30,
30, 150, 30,
0, 150, 0,
30, 150, 30,
30, 150, 0,
// left side
0, 0, 0,
0, 0, 30,
0, 150, 30,
0, 0, 0,
0, 150, 30,
0, 150, 0]),
gl.STATIC_DRAW);
}
// Fill the buffer with colors for the 'F'.
function setColors(gl) {
gl.bufferData(
gl.ARRAY_BUFFER,
new Uint8Array([
// left column front
200, 70, 120,
200, 70, 120,
200, 70, 120,
200, 70, 120,
200, 70, 120,
200, 70, 120,
// top rung front
200, 70, 120,
200, 70, 120,
200, 70, 120,
200, 70, 120,
200, 70, 120,
200, 70, 120,
// middle rung front
200, 70, 120,
200, 70, 120,
200, 70, 120,
200, 70, 120,
200, 70, 120,
200, 70, 120,
// left column back
80, 70, 200,
80, 70, 200,
80, 70, 200,
80, 70, 200,
80, 70, 200,
80, 70, 200,
// top rung back
80, 70, 200,
80, 70, 200,
80, 70, 200,
80, 70, 200,
80, 70, 200,
80, 70, 200,
// middle rung back
80, 70, 200,
80, 70, 200,
80, 70, 200,
80, 70, 200,
80, 70, 200,
80, 70, 200,
// top
70, 200, 210,
70, 200, 210,
70, 200, 210,
70, 200, 210,
70, 200, 210,
70, 200, 210,
// top rung right
200, 200, 70,
200, 200, 70,
200, 200, 70,
200, 200, 70,
200, 200, 70,
200, 200, 70,
// under top rung
210, 100, 70,
210, 100, 70,
210, 100, 70,
210, 100, 70,
210, 100, 70,
210, 100, 70,
// between top rung and middle
210, 160, 70,
210, 160, 70,
210, 160, 70,
210, 160, 70,
210, 160, 70,
210, 160, 70,
// top of middle rung
70, 180, 210,
70, 180, 210,
70, 180, 210,
70, 180, 210,
70, 180, 210,
70, 180, 210,
// right of middle rung
100, 70, 210,
100, 70, 210,
100, 70, 210,
100, 70, 210,
100, 70, 210,
100, 70, 210,
// bottom of middle rung.
76, 210, 100,
76, 210, 100,
76, 210, 100,
76, 210, 100,
76, 210, 100,
76, 210, 100,
// right of bottom
140, 210, 80,
140, 210, 80,
140, 210, 80,
140, 210, 80,
140, 210, 80,
140, 210, 80,
// bottom
90, 130, 110,
90, 130, 110,
90, 130, 110,
90, 130, 110,
90, 130, 110,
90, 130, 110,
// left side
160, 160, 220,
160, 160, 220,
160, 160, 220,
160, 160, 220,
160, 160, 220,
160, 160, 220]),
gl.STATIC_DRAW);
}
main();
</script>
</html>