Dendrite growth using d3 quadchart nearest neighbor search.
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August 29, 2015 14:03
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Dendrite Growth - nearest neighbor search using d3 quadtree
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| body { | |
| background: rgb(255, 255, 255); | |
| } | |
| </style> | |
| <body> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 500, | |
| maxRadius = 8; | |
| var makePoint = pointBuilder(maxRadius, width, height); | |
| var svg = d3.select("body") | |
| .append("svg") | |
| .attr({width: width, height: height}); | |
| var seedPoints = [ | |
| [width/2, height/2, 3] | |
| ]; | |
| var sample = findClosest(seedPoints, width, height, 1000); | |
| var circles = svg.append("g"); | |
| var lines = svg.append("g"); | |
| circles.selectAll("circle") | |
| .data(seedPoints) | |
| .enter() | |
| .append("circle") | |
| .attr({ | |
| cx: function(d, i) { return d[0]; }, | |
| cy: function(d, i) { return d[1]; }, | |
| r: function(d, i) { return d[2]; }, | |
| fill: "rgb(0, 0, 0)", | |
| opacity: 0 | |
| }) | |
| d3.timer(function() { | |
| for(var i = 0; i < 7; i++) { | |
| var p = makePoint(); | |
| var s = sample(p); | |
| if(!s) return true; | |
| var nearest = s[0]; | |
| var moveTo = s[1]; | |
| circles.append("circle") | |
| .attr({ | |
| r: 0, | |
| cx: nearest[0], | |
| cy: nearest[1], | |
| fill: "rgb(0, 0, 0)", | |
| opacity: 0 | |
| }) | |
| .transition() | |
| .attr({ | |
| r: moveTo[2], | |
| cx: moveTo[0], | |
| cy: moveTo[1], | |
| opacity: 1 | |
| }); | |
| lines.append("line") | |
| .attr({ | |
| stroke: "rgba(255, 0, 0, 1)", | |
| x1: nearest[0], | |
| y1: nearest[1], | |
| x2: nearest[0], | |
| y2: nearest[1] | |
| }) | |
| .transition() | |
| .attr({ | |
| x1: nearest[0], | |
| y1: nearest[1], | |
| x2: moveTo[0], | |
| y2: moveTo[1] | |
| }); | |
| } | |
| }); | |
| function findClosest(seedPoints, width, height, maxSamples) { | |
| var samples = 0; | |
| var quadtree = d3.geom.quadtree() | |
| .extent([[-1, -1], [width+1, height+1]])(seedPoints); | |
| var points = seedPoints; | |
| return function(d) { | |
| var x = d[0], | |
| y = d[1], | |
| r = d[2]; | |
| if(++samples > maxSamples) return; | |
| var nearest, minDistance = Math.sqrt(width*width + height*height); | |
| quadtree.visit(function(node, x1, y1, x2, y2) { | |
| var p = node.point; | |
| if(p) { | |
| var d = dist(p[0], p[1], x, y); | |
| if(d < minDistance) { | |
| nearest = p; | |
| minDistance = d; | |
| } | |
| else { | |
| return true; | |
| } | |
| } | |
| }); | |
| var dx = x - nearest[0]; | |
| var dy = y - nearest[1]; | |
| var t = Math.atan2(dy, dx); | |
| var moveToX = nearest[0] + (r + nearest[2]) * Math.cos(t); | |
| var moveToY = nearest[1] + (r + nearest[2]) * Math.sin(t); | |
| var moveTo = [moveToX, moveToY, r]; | |
| quadtree.add(moveTo); | |
| points.push(moveTo); | |
| return [nearest, moveTo]; | |
| }; | |
| } | |
| function pointBuilder(maxRadius, width, height) { | |
| return function() { | |
| return [ | |
| Math.random() * width, | |
| Math.random() * height, | |
| 1 + Math.random() * (maxRadius-1) | |
| ]; | |
| }; | |
| } | |
| // calculate euclidean distance of two points with coordinates: a(ax, ay) and b(bx, by) | |
| function dist(ax, ay, bx, by){ | |
| return Math.sqrt(Math.pow(ax-bx, 2) + Math.pow(ay-by, 2)); | |
| } | |
| </script> |
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