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<!doctype html>
<html>
<body>
<style>
body {
background: #333;
margin: 0;
padding: 0;
width: 100%;
height: 100%;
}
#demo {
margin: 20px;
width: 800px;
height: 600px;
position: relative;
}
canvas {
display: block;
top: 0;
left: 0;
position: absolute;
width: 100%;
height: 100%;
}
#ctrls {
margin: 20px;
width: 800px;
}
h1, p {
color: #0066cc;
margin: 20px;
font-family: monospace;
}
h1 span {
color: #fff;
}
p, a {
color: #fff;
line-height: 1.5em;
font-size: 1.15em;
}
a {
color: #0066cc;
}
</style>
<h1>HTML5 Canvas 2D API Suggestion: <span>Custom Shader</span></h1>
<div id="demo"></div>
<div id="ctrls"></div>
<p>Copyright © 2013 <a href="http://www.rodrigo-silveira.com">Rodrigo Silveira</a>. All rights reserved. Mega Man
is an awesome game, and all its rights, trademarks, etc. are property of Capcom.</p>
<script>
/**
* @overview The purpose of this demonstration is to illustrate one of the benefits that can be gained by being able
* to specify a custom fragment shader into the CanvasRenderingContext2D object.
*
* What the following application does is simulate such functionality by using functions as post-processors,
* which, when set, perform some transformation to the pixel data contained in a CanvasRenderingContext2D.
* Ideally, this would all be done at the GPU, by means of a user-specified fragment shader.
*
* @author Rodrigo Silveira <webmaster@rodrigo-sileira.com>
*/
/**
* Make it so references to this function kind of look like a GLSL file
*
* @type {Object.<string, Function>}
*/
var allBlackShader = {};
allBlackShader.glsl = function () {
var img = this.getImageData(0, 0, WIDTH, HEIGHT);
var data = img.data;
for (var i = 0, len = data.length; i < len; i += 4) {
data[i] = data[i + 1] = data[i + 2] = 255 - data[i + 3];
}
this.putImageData(img, 0, 0);
setTimeout(function () {
doThunder = false;
}, 150);
};
var allWhiteShader = {};
allWhiteShader.glsl = function () {
var img = this.getImageData(0, 0, WIDTH, HEIGHT);
var data = img.data;
for (var i = 0, len = data.length; i < len; i += 4) {
data[i] = data[i + 1] = data[i + 2] = data[i + 3];
}
this.putImageData(img, 0, 0);
setTimeout(function () {
doThunder = false;
}, 150);
};
var defShader = {};
defShader.glsl = function () {
return 0;
};
/**
* Some application-level convenience function that determines what shader is wanted based on some condition
*
* @param {string} name
* @returns {Function}
*/
function getAppropriateShaderProgram(name) {
if (doThunder) {
if (name == Layers.BACKGROUND) {
return CanvasRenderingContext2D.customShaderPrograms[name];
}
if (name == Layers.FOREGROUND) {
return CanvasRenderingContext2D.customShaderPrograms[name];
}
}
return CanvasRenderingContext2D.customShaderPrograms[0];
}
//
// What this API could possibly look like... why not?!
//
/**
* Set up default shader program. Note the fake reference to a GLSL "file"
*
* @type {Array.<Function>}
*/
CanvasRenderingContext2D.customShaderPrograms = [defShader.glsl];
/**
* Each canvas context has its own custom shader. Note the cute addition of the fake [and out of place] dev prefix =)
*
* @type {Function}
*/
CanvasRenderingContext2D.prototype["-rokko-customShader"] = defShader;
/**
* Some "internal" hook for the custom shader to run (only needed in the implementation of this demo.
* The dream is that each draw call on the ctx instance would be done using whatever program is currently bound
*
*/
CanvasRenderingContext2D.prototype.runCustomShader = function () {
this["-rokko-customShader"].call(this);
};
/**
* Compile a shader program and return a pointer to it
*
* @param {Function} fragmentShader
* @param {null} vertexShader
* @returns {number}
*/
CanvasRenderingContext2D.prototype.compileCustomShader = function (fragmentShader, vertexShader) {
CanvasRenderingContext2D.customShaderPrograms.push(fragmentShader);
return CanvasRenderingContext2D.customShaderPrograms.length - 1;
};
CanvasRenderingContext2D.prototype.bindCustomShader = function (shaderProgram) {
this["-rokko-customShader"] = shaderProgram;
};
var WIDTH = 800;
var HEIGHT = 600;
var MAX_RAIN = 108;
var isPaused = false;
var doThunder = false;
var shaders = {};
var Layers = {};
function main() {
var canvas = document.createElement("canvas");
canvas.width = WIDTH;
canvas.height = HEIGHT;
var ctx = canvas.getContext("2d");
ctx.webkitImageSmoothingEnabled = false;
var canvas2 = document.createElement("canvas");
canvas2.width = WIDTH;
canvas2.height = HEIGHT;
var ctx2 = canvas2.getContext("2d");
/**
* Compiile shader program and hold on to its pointer
*
* @type {number}
*/
shaders.allBlack = ctx2.compileCustomShader(allWhiteShader.glsl);
shaders.allWhite = ctx.compileCustomShader(allBlackShader.glsl);
Layers.FOREGROUND = shaders.allWhite;
Layers.BACKGROUND = shaders.allBlack;
var imgs = {
rain: new Image(),
mm: new Image(),
floor: new Image(),
bg: new Image()
};
imgs.rain.src = "/img/rain.png";
imgs.mm.src = "/img/8bitmm.gif";
imgs.floor.src = "img/mm-level-4.png";
imgs.bg.src = "img/mm-level-4.png";
var megaman = {
x: WIDTH * 0.25,
y: 426,
width: 64,
height: 64,
speed: 3,
scale: 3,
currFrame: 0,
frames: [
{
pos: {
x: 190,
y: 11
},
size: {
w: 24,
h: 24
},
freq: 100
},
{
pos: {
x: 220,
y: 11
},
size: {
w: 16,
h: 24
},
freq: 100
},
{
pos: {
x: 241,
y: 11
},
size: {
w: 21,
h: 24
},
freq: 100
}
]
};
function createBlock(x, y, w, h) {
return block = {
x: x,
y: y,
width: w,
height: h,
pos: {
x: 168,
y: 120
},
size: {
w: 48,
h: 102
}
};
}
function createSky(x, y, w, h) {
return block = {
x: x,
y: y,
width: w,
height: h,
pos: {
x: 2,
y: 2
},
size: {
w: 150,
h: 150
}
};
}
var MAX_FLOOR = 20;
var floor = [];
for (var i = 0; i < MAX_FLOOR; i++) {
floor[i] = createBlock(i * 48, 600 - 102, 48, 102);
}
var bg = createSky(0, 0, 600, 500);
var bg2 = createSky(600, 0, 600, 500);
var rains = [];
for (var i = 0; i < MAX_RAIN; i++) {
rains[i] = {
width: parseInt(Math.random() * 1 + 1),
height: parseInt(Math.random() * 55 + 10),
x: parseInt(Math.random() * WIDTH),
y: parseInt(Math.random() * HEIGHT),
speed: Math.random() * 10 + 3
}
}
var lastTime = 0;
var freq = 1000 / 30;
var soundFX = {
rain: new Audio("/sound/rain.mp3"),
thunder: [
new Audio("/sound/thunder2.mp3"),
new Audio("/sound/thunder3.mp3")
]
};
soundFX.rain.loop = true;
var btnThunder = document.createElement("button");
btnThunder.textContent = "Thunder";
btnThunder.addEventListener("click", function () {
doThunder = !doThunder;
if (doThunder) {
soundFX.thunder[0].currentTime = 0.40;
soundFX.thunder[0].volume = 1.00;
soundFX.thunder[0].play();
doThunder = false;
setTimeout(function(){
doThunder = true;
}, 500);
}
}, false);
var btnRun = document.createElement("button");
btnRun.textContent = "Pause";
btnRun.addEventListener("click", function () {
isPaused = !isPaused;
render(0);
}, false);
document.getElementById("ctrls").appendChild(btnThunder);
document.getElementById("ctrls").appendChild(btnRun);
document.getElementById("demo").appendChild(canvas2);
document.getElementById("demo").appendChild(canvas);
function renderBackground(time) {
ctx.clearRect(0, 0, WIDTH, HEIGHT);
// ctx2.fillStyle = "000";
// ctx2.fillRect(0, 0, WIDTH, HEIGHT);
// ctx2.fill();
ctx2.drawImage(imgs.bg, bg.pos.x, bg.pos.y, bg.size.w, bg.size.h, bg.x, bg.y, bg.width, bg.height);
ctx2.drawImage(imgs.bg, bg2.pos.x, bg2.pos.y, bg2.size.w, bg2.size.h, bg2.x, bg2.y, bg2.width, bg2.height);
ctx2.runCustomShader();
}
function renderForeground(time) {
for (var i = 0; i < MAX_FLOOR; i++) {
ctx.drawImage(imgs.floor, floor[i].pos.x, floor[i].pos.y, floor[i].size.w, floor[i].size.h, floor[i].x, floor[i].y, floor[i].width, floor[i].height);
}
var frame = megaman.frames[megaman.currFrame];
if (time - lastTime >= frame.freq) {
megaman.currFrame = (megaman.currFrame + 1) % megaman.frames.length;
lastTime = time;
}
megaman.x += megaman.speed;
if (megaman.x > WIDTH + megaman.width) {
megaman.x = 0 - megaman.width;
}
ctx.drawImage(imgs.mm, frame.pos.x, frame.pos.y, frame.size.w, frame.size.h, megaman.x, megaman.y, frame.size.w * megaman.scale, frame.size.h * megaman.scale);
for (var i = 0, rain; i < MAX_RAIN; i++) {
rain = rains[i];
rain.y = (rain.y + rain.speed) % (HEIGHT + rain.height);
ctx.drawImage(imgs.rain, rain.x, rain.y, rain.width, rain.height);
}
ctx.runCustomShader();
}
function render(time) {
if (time - lastTime >= freq) {
ctx2.bindCustomShader(getAppropriateShaderProgram(Layers.BACKGROUND));
renderBackground(time);
ctx.bindCustomShader(getAppropriateShaderProgram(Layers.FOREGROUND));
renderForeground(time);
}
if (!isPaused) {
requestAnimationFrame(render);
}
}
soundFX.rain.volume = 0.5;
soundFX.rain.play();
render(0);
}
main();
</script>
</body>
</html>