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webgl-text-texture-consistent-scale.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 - Textures - Consistent Size</title>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
<style>
* {
box-sizing: border-box;
}
#ui {
width: 200px;
}
</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>
<script src="resources/primitives.js"></script>
</head>
<body>
<canvas id="canvas"></canvas>
</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 id="text-vertex-shader" type="x-shader/x-vertex">
attribute vec4 a_position;
attribute vec2 a_texcoord;
uniform mat4 u_matrix;
varying vec2 v_texcoord;
void main() {
// Multiply the position by the matrix.
gl_Position = u_matrix * a_position;
// Pass the texcoord to the fragment shader.
v_texcoord = a_texcoord;
}
</script>
<!-- fragment shader -->
<script id="text-fragment-shader" type="x-shader/x-fragment">
precision mediump float;
// Passed in from the vertex shader.
varying vec2 v_texcoord;
uniform sampler2D u_texture;
void main() {
gl_FragColor = texture2D(u_texture, v_texcoord);
}
</script>
<script>
"use strict";
var textCtx = document.createElement("canvas").getContext("2d");
// Puts text in center of canvas.
function makeTextCanvas(text, width, height) {
textCtx.canvas.width = width;
textCtx.canvas.height = height;
textCtx.font = "20px monospace";
textCtx.textAlign = "center";
textCtx.textBaseline = "middle";
textCtx.fillStyle = "black";
textCtx.clearRect(0, 0, textCtx.canvas.width, textCtx.canvas.height);
textCtx.fillText(text, width / 2, height / 2);
return textCtx.canvas;
}
function main() {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
var canvas = document.querySelector("#canvas");
var gl = canvas.getContext("webgl");
if (!gl) {
return;
}
// Create data for 'F'
var fBufferInfo = primitives.create3DFBufferInfo(gl);
// Create a unit quad for the 'text'
var textBufferInfo = primitives.createPlaneBufferInfo(gl, 1, 1, 1, 1, m4.xRotation(Math.PI / 2));
// setup GLSL programs
var fProgramInfo = webglUtils.createProgramInfo(gl, ["vertex-shader-3d", "fragment-shader-3d"]);
var textProgramInfo = webglUtils.createProgramInfo(gl, ["text-vertex-shader", "text-fragment-shader"]);
// create text texture.
var textCanvas = makeTextCanvas("Hello World!", 150, 26);
var textWidth = textCanvas.width;
var textHeight = textCanvas.height;
var textTex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, textTex);
gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, true);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, textCanvas);
// make sure we can render it even if it's not a power of 2
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);
var fUniforms = {
u_matrix: m4.identity(),
};
var textUniforms = {
u_matrix: m4.identity(),
u_texture: textTex,
};
function radToDeg(r) {
return r * 180 / Math.PI;
}
function degToRad(d) {
return d * Math.PI / 180;
}
var translation = [0, 30, 0];
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(now) {
// Convert to seconds
now *= 0.001;
// Subtract the previous time from the current time
var deltaTime = now - then;
// Remember the current time for the next frame.
then = now;
webglUtils.resizeCanvasToDisplaySize(gl.canvas);
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// Every frame increase the rotation a little.
rotation[1] += rotationSpeed * deltaTime;
gl.enable(gl.CULL_FACE);
gl.enable(gl.DEPTH_TEST);
gl.disable(gl.BLEND);
gl.depthMask(true);
// Clear the canvas AND the depth buffer.
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Compute the matrices used for all objects
var aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
var projectionMatrix =
m4.perspective(fieldOfViewRadians, aspect, 1, 2000);
// Compute the camera's matrix using look at.
var cameraRadius = 360;
var cameraPosition = [Math.cos(now) * cameraRadius, 0, Math.sin(now) * cameraRadius];
var target = [0, 0, 0];
var up = [0, 1, 0];
var cameraMatrix = m4.lookAt(cameraPosition, target, up);
var viewMatrix = m4.inverse(cameraMatrix);
var textPositions = [];
// setup to draw the 'F'
gl.useProgram(fProgramInfo.program);
webglUtils.setBuffersAndAttributes(gl, fProgramInfo, fBufferInfo);
// draw the Fs.
var spread = 170;
for (var yy = -1; yy <= 1; ++yy) {
for (var xx = -2; xx <= 2; ++xx) {
var fViewMatrix = m4.translate(viewMatrix,
translation[0] + xx * spread, translation[1] + yy * spread, translation[2]);
fViewMatrix = m4.xRotate(fViewMatrix, rotation[0]);
fViewMatrix = m4.yRotate(fViewMatrix, rotation[1] + yy * xx * 0.2);
fViewMatrix = m4.zRotate(fViewMatrix, rotation[2] + now + (yy * 3 + xx) * 0.1);
fViewMatrix = m4.scale(fViewMatrix, scale[0], scale[1], scale[2]);
fViewMatrix = m4.translate(fViewMatrix, -50, -75, 0);
textPositions.push([fViewMatrix[12], fViewMatrix[13], fViewMatrix[14]]);
fUniforms.u_matrix = m4.multiply(projectionMatrix, fViewMatrix);
webglUtils.setUniforms(fProgramInfo, fUniforms);
// Draw the geometry.
gl.drawElements(gl.TRIANGLES, fBufferInfo.numElements, gl.UNSIGNED_SHORT, 0);
}
}
gl.enable(gl.BLEND);
gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
gl.depthMask(false);
// setup to draw the text.
gl.useProgram(textProgramInfo.program);
webglUtils.setBuffersAndAttributes(gl, textProgramInfo, textBufferInfo);
textPositions.forEach(function(pos) {
// draw the text
// use just the view position of the 'F' for the text
// because pos is in view space that means it's a vector from the eye to
// some position. So translate along that vector back toward the eye some distance
var fromEye = m4.normalize(pos);
var amountToMoveTowardEye = 150; // because the F is 150 units long
var viewX = pos[0] - fromEye[0] * amountToMoveTowardEye;
var viewY = pos[1] - fromEye[1] * amountToMoveTowardEye;
var viewZ = pos[2] - fromEye[2] * amountToMoveTowardEye;
var desiredTextScale = -1 / gl.canvas.height; // 1x1 pixels
var scale = viewZ * desiredTextScale;
var textMatrix = m4.translate(projectionMatrix, viewX, viewY, viewZ);
// scale the F to the size we need it.
textMatrix = m4.scale(textMatrix, textWidth * scale, textHeight * scale, 1);
m4.copy(textMatrix, textUniforms.u_matrix);
webglUtils.setUniforms(textProgramInfo, textUniforms);
// Draw the text.
gl.drawElements(gl.TRIANGLES, textBufferInfo.numElements, gl.UNSIGNED_SHORT, 0);
});
requestAnimationFrame(drawScene);
}
}
main();
</script>
</html>