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graph4.html
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<html>
<!--
author: Alexey Utkin
email: alexey.utkin@gmail.com
-->
<head>
<title>My God, it's full of stars!</title>
<script type="text/javascript">
var el;
var ctx;
var pixels;
var w;
var h;
var fps = 100;
var maxQ = 10;
var maxMassQ = 2;
var cBody = 25;
function init() {
el = document.getElementById('game');
w = el.width;
h = el.height;
ctx = el.getContext('2d');
pixels = ctx.createImageData(w, h);
for ( var i = 0; i < w*h; ++i) {
pixels.data[i*4 + 3] = 255;
}
initModel();
setInterval(clock, 1000 / fps);
};
function clock() {
renderScene();
ctx.putImageData(pixels, 0, 0);
renderModel();
};
var arFX = new Array(cBody);
var arFY = new Array(cBody);
var arVX = new Array(cBody);
var arVY = new Array(cBody);
var arX = new Array(cBody);
var arY = new Array(cBody);
var arQ = new Array(cBody);
var M = 0;
function initModel() {
for (var i = 0; i < cBody; ++i) {
arQ[i] = 1 + Math.random() * (maxQ - 1);
M += arQ[i];
arX[i] = w * Math.random();
arY[i] = h * Math.random();
arVX[i] = Math.random() * w / (5 * fps);
arVY[i] = Math.random() * h / (5 * fps);
}
}
function ss(x1, y1, x2, y2) {
return x1*x2 + y1*y2;
}
function modul(x, y) {
return Math.sqrt(x*x + y*y);
}
function doModel() {
for (var i = 0; i < cBody; ++i) {
arX[i] += arVX[i];
arY[i] += arVY[i];
if (arX[i] < 0 || arX[i] > w)
arVX[i] *= -1;
if (arY[i] < 0 || arY[i] > h)
arVY[i] *= -1;
arFX[i] = 0;
arFY[i] = 0;
}
for (var i = 0; i < cBody; ++i) {
for (var k = 0; k < i; ++k) {
var dx = arX[k] - arX[i];
var dy = arY[k] - arY[i];
var r2 = (dx * dx + dy * dy);
var r = Math.sqrt(r2);
if (r < (arQ[i] + arQ[k])/maxMassQ) {
//Time machine -2 dt
var dox = dx - (arVX[k] - arVX[i]) * 2;
var doy = dy - (arVY[k] - arVY[i]) * 2;
var orm = modul(dox, doy);
//Ellastic collision
var nx = dox/orm;
var ny = doy/orm;
var un_ss = ss(arVX[i], arVY[i], nx, ny);
var m = arQ[i];
var Un_ss = ss(arVX[k], arVY[k], nx, ny);
var M = arQ[k];
var vn_ss = (un_ss*(m - M) + 2*M*Un_ss)/(m + M);
var Vn_ss = (Un_ss*(M - m) + 2*m*un_ss)/(m + M);
arVX[i] += (vn_ss - un_ss)*nx;
arVY[i] += (vn_ss - un_ss)*ny;
arVX[k] += (Vn_ss - Un_ss)*nx;
arVY[k] += (Vn_ss - Un_ss)*ny;
} else {
var nx = dx / r;
var ny = dy / r;
var F = arQ[k] / r2;
arFX[i] += F * nx;
arFY[i] += F * ny;
F = arQ[i] / r2;
arFX[k] -= F * nx;
arFY[k] -= F * ny;
}
}
}
for (var i = 0; i < cBody; ++i) {
arVX[i] += arFX[i];
arVY[i] += arFY[i];
}
}
function FF(x, y) {
var F = 0.0;
for (var i = 0; i < cBody; ++i) {
if (x == arX[i] || y == arY[i])
return arQ[i];
var r = modul(x - arX[i], y - arY[i]);
F += arQ[i] / r;
}
return F;
}
function renderScene() {
doModel();
for (var x = 0; x < w; ++x) {
for (var y = 0; y < h; ++y) {
var F = 65*FF(x, y);
var off = (x + y * w) * 4;
pixels.data[off + 0] = F;
//pixels.data[off + 1] = 0;
//pixels.data[off + 2] = 0;
}
}
}
function renderModel() {
var mX = 0;
var mY = 0;
for (var i = 0; i < cBody; ++i) {
mX += arQ[i] * arX[i];
mY += arQ[i] * arY[i];
ctx.beginPath();
ctx.arc(arX[i], arY[i], arQ[i]/maxMassQ, 0, 2*Math.PI, false);
ctx.fillStyle = "rgb(0, 200," + Math.round(arQ[i]*255/maxQ) + ")";
ctx.fill();
ctx.lineWidth = 0.01;
ctx.stroke();
}
mX /= M;
mY /= M;
ctx.fillStyle = "#0000FF";
ctx.fillRect(mX - 2, mY - 2, 4, 4);
}
</script>
<style type="text/css">
canvas, img {
image-rendering: optimizeSpeed;
image-rendering: -moz-crisp-edges;
image-rendering: -webkit-optimize-contrast;
image-rendering: optimize-contrast;
-ms-interpolation-mode: nearest-neighbor;
}
</style>
</head>
<body>
<canvas id="game" width="300" height="300"></canvas>
<script type="text/javascript">init();</script>
</body>
</html>