raidiun.github.io/grav.html at master · raidiun/raidiun.github.io · GitHub

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<html>
	<head>
		<style type="text/css">
			body {
				background-color: black;
				margin:0;
				width:100%;
				height:100%;
				}
			#main {
				width:100%;
				height:100%;
				}
		</style>
	</head>
	<body>
		<canvas id="main" width="1500" height="1500"></canvas>
		<script type="text/javascript">
			 var canvas = document.getElementById("main");
			 var ctx = canvas.getContext("2d");

			 var orbs = [];

			 function omd(e) {
				canvasBCR = canvas.getBoundingClientRect();
				var cx,cy;
				if(e.type == 'mousedown') {
					cx = e.clientX;
					cy = e.clientY;
					}
				else {
					cx = e.touches[0].clientX;
					cy = e.touches[0].clientY;
					}
				var x = 1500.0*(cx-canvasBCR.left)/(canvasBCR.right-canvasBCR.left);
				var y = 1500.0*(cy-canvasBCR.top)/(canvasBCR.bottom-canvasBCR.top);
				orbs.push(new Orb(x,y, 0, 30, 100));
				}

			 canvas.addEventListener("mousedown",omd);
			 //canvas.addEventListener("touchstart",omd);

			 function Orb(x, y, dx, dy, mass) {
			 this.x = x;
			 this.y = y;
			 this.dx = dx;
			 this.dy = dy;
			 this.mass = mass;

			 this.path = [];

			 this.radius = Math.sqrt(this.mass);
			 }

			 var orbFrameCount = 0;
			 var fpsUpdateRate = 500; // ms
			 var lastFpsUpdate = 0;

			 var physicsUpdateRate = 1000/120.0;
			 var lastPhysicsUpdate = 0;
			 var physicsFrameCount = 0;

			 var time = new Date().getTime();

			 function ran(min, max) {
			 return Math.floor(Math.random() * (max - min + 1)) + min;
			 }

			 var G = 0.5;

			 var trailcount = 200;

			 function updateOrbs(dt) {
			 var dtsec = dt/1000.0;
			 for(var i in orbs) {
			 var orb1 = orbs[i];

			 for(var j in orbs) {
			 if(i === j) continue;

			 var orb2 = orbs[j];

			 var dvec = { // distance vector between orb1 and orb2
			 x: orb2.x-orb1.x,
			 y: orb2.y-orb1.y
			 };

			 // distance between orb1 and orb2 squared
			 var r = Math.sqrt(Math.pow(dvec.x, 2) + Math.pow(dvec.y, 2));
			 // acceleration on orb1
			 var a = (G * orb2.mass)/(r);

			 var ndvec = { // dvec normalised
			 x: dvec.x/r,
			 y: dvec.y/r
			 };

			 orb1.dx += ndvec.x * a;
			 orb1.dy += ndvec.y * a;
			 }

			 orb1.path.push({x:orb1.x, y:orb1.y});
			 if(orb1.path.length > trailcount) orb1.path.shift();


			 }

			 for(var k in orbs) {
			 var orb = orbs[k];
			 orb.x += orb.dx * dtsec;
			 orb.y += orb.dy * dtsec;

			 if(orb.x > 1500) orb.x = 0;
			 if(orb.x < 0) orb.x = 1500;
			 if(orb.y > 1500) orb.y = 0;
			 if(orb.y < 0) orb.y = 1500;
			 }

			 physicsFrameCount++;
			 }

			 function renderOrbs() {
			 clearOrbs();

			 for(var i in orbs) {
			 var orb = orbs[i];
			 drawOrb(orb);
			 }
			 orbFrameCount++;
			 function drawOrb(orb) {
			 orb.lastX = orb.x;
			 orb.lastY = orb.y;

			 for(var i = 0; i < orb.path.length; i+=2) {
			 var ghost = orb.path[i];
			 var size = tailfn(orb, i);
			 if(size > 0.4)
			 drawCircle(ghost.x, ghost.y, size, "rgba(102, 153, 204, 1)");
			 }

			 drawCircle(orb.x, orb.y, orb.radius, "#FFFFFF");
			 }
			 }

			 function tailfn(orb, i) {
			 return (i/trailcount)*orb.radius;
			 }


			 function clearOrbs() {
			 for(var i in orbs) {
			 var orb = orbs[i];
			 clearOrb(orb);
			 }

			 function clearOrb(orb) {
			 var clearPadding = 2;
			 drawCircle(orb.lastX, orb.lastY, orb.radius + 2, "#000000");

			 var minx = 10000,
			 maxx = 0,
			 miny = 10000,
			 maxy = 0;

			 for(var i in orb.path) {
			 var ghost = orb.path[i];
			 var r = orb.radius;
			 if(ghost.x-r < minx)  minx = ghost.x-r;
			 if(ghost.x+r > maxx)  maxx = ghost.x+r;
			 if(ghost.y-r < miny)  miny = ghost.y-r;
			 if(ghost.y+r > maxy)  maxy = ghost.y+r;
			 }
			 ctx.fillStyle = "#000000";
			 var buffer = 2;
			 ctx.fillRect(minx - buffer, miny - buffer, maxx-minx + 2*buffer, maxy-miny + 2*buffer);
			 }
			 }

			 function renderFps() {
			 clearFps();
			 ctx.font="20px Georgia";
			 ctx.fillStyle = "#FFFFFF";
			 ctx.fillText((orbFrameCount/(fpsUpdateRate/1000.0)) + " drawfps",1250,25);
			 ctx.fillText((physicsFrameCount/(fpsUpdateRate/1000.0)) + " updatefps",1250,50);

			 orbFrameCount = 0;
			 physicsFrameCount = 0;
			 function clearFps() {
			 ctx.fillStyle = "#000000";
			 ctx.fillRect(1250,7,140,50);
			 }
			 }
			 function drawCircle(x, y, r, c) {
			 ctx.fillStyle = c;
			 ctx.beginPath();
			 ctx.arc(x, y, r, 0, Math.PI*2, true);
			 ctx.closePath();
			 ctx.fill();
			 }

			 (function loop() {
			  window.webkitRequestAnimationFrame(loop);
			  var now = new Date().getTime();
			  var dt = now - time;
			  if(dt > 20) dt = 20; // update slow if running slow

			  // updating
			  //if((now-lastPhysicsUpdate) > physicsUpdateRate) {
			  updateOrbs(dt);
			  //lastPhysicsUpdate = now;
			  //}

			  // rendering
			  renderOrbs();
			  //if((now - lastFpsUpdate) > fpsUpdateRate) {
			  //renderFps();
			  //lastFpsUpdate = now;
			  //}

			  time = now;
			  //setTimeout(loop, 0);
			  })();

			</script>
	</body>

</html>