Add circles collision solving function

docs_src/js/circles.js

@@ -0,0 +1,103 @@
+window.solveCollision = function(circles, opts) {
+	opts = opts || {};
+	var tree = d3.quadtree()
+		.x(function(d) {return d.xp;})
+		.y(function(d) {return d.yp;});
+	if (opts.extent !== undefined) tree.extent(opts.extent);
+	var rMax = 0;
+	circles.forEach(function(circle) {
+		circle.xp = circle.x0;
+		circle.yp = circle.y0;
+		if (opts.r0 !== undefined) circle.r0 = opts.r0;
+		circle.r = circle.r0;
+		circle.xMin = circle.x0 - circle.r0;
+		circle.xMax = circle.x0 + circle.r0;
+		circle.yMin = circle.y0 - circle.r0;
+		circle.yMax = circle.y0 + circle.r0;
+
+		function collide(d) {
+			function fixCollision(node) {
+				var x = d.xp - node.xp;
+				var y = d.yp - node.yp;
+				var l = x * x + y * y;
+				var r = d.r + node.r;
+				if (l < r * r) {
+					var c1, c2, lambda1, lambda2, u1, u2;
+					var delta = Math.sqrt(l);
+					if (d.r < node.r) {
+						c1 = node; c2 = d;
+					} else {
+						c1 = d; c2 = node;
+					}
+					var r1 = c1.r;
+					var r2 = c2.r;
+					var alpha = (r1 + r2 + delta) / 4;
+					if (l > 0) {
+						u1 = (c2.xp - c1.xp) / delta;
+						u2 = (c2.yp - c1.yp) / delta;
+					} else {
+						var theta = 2 * Math.PI * Math.random();
+						u1 = Math.cos(theta);
+						u2 = Math.sin(theta);
+					}
+
+					if (r2 >= alpha) {
+						lambda1 = alpha / r1;
+						lambda2 = alpha / r2;
+					} else {
+						lambda1 = (r1 - r2 + delta) / (2 * r1);
+						if (lambda1 > 1) console.log(lambda1);
+						lambda2 = 1;
+					}
+					c1.r *= lambda1;
+					c2.r *= lambda2;
+					c1.xp += (lambda1 - 1) * r1 * u1;
+					c1.yp += (lambda1 - 1) * r1 * u2;
+					c2.xp += (1 - lambda2) * r2 * u1;
+					c2.yp += (1 - lambda2) * r2 * u2;
+					c1.xMin = c1.xp - c1.r;
+					c1.xMax = c1.xp + c1.r;
+					c1.yMin = c1.yp - c1.r;
+					c1.yMax = c1.yp + c1.r;
+					c2.xMin = c2.xp - c2.r;
+					c2.xMax = c2.xp + c2.r;
+					c2.yMin = c2.yp - c2.r;
+					c2.yMax = c2.yp + c2.r;
+				}
+			}
+			return function(quad, x1, y1, x2, y2) {
+				if (!quad.length) {
+					do {
+						if (quad.data != d && d.xMax > quad.data.xMin && d.xMin < quad.data.xMax && d.yMax > quad.data.yMin && d.yMin < quad.data.yMax) {
+							fixCollision(quad.data);
+						}
+					} while (quad = quad.next)
+				}
+				return x1 > d.xMax + rMax || x2 + rMax < d.xMin || y1 > d.yMax + rMax || y2 + rMax < d.yMin;
+			};
+		}
+		tree.visit(collide(circle));
+		rMax = Math.max(rMax, circle.r);
+		tree.add(circle);
+	});
+	if (opts.zoom !== undefined) {
+		circles.forEach(function(circle) {
+			circle.cache = circle.cache || {};
+			circle.cache[opts.zoom] = {
+				x: circle.xp,
+				y: circle.yp,
+				r: circle.r
+			};
+		});
+	}
+	var ret = d3.quadtree()
+		.x(function(d) {return d.xp;})
+		.y(function(d) {return d.yp;});
+	var rMax2 = 0;
+	circles.forEach(function(circle) {
+		ret.add(circle);
+		rMax2 = Math.max(rMax2, circle.r);
+	})
+	ret.rMax = rMax2;
+	return ret;
+}