This example shows how geometries with inner loops and outer loops build themselves in opposite direction. The outer loop (red) builds clockwise, while the inner loop (blue) builds counter-clockwise. This is important in order to confidently account for negative MultiPolygons instead of separate Polygon features. Here's a good summary of the importance in winding order.
Created
December 14, 2015 19:30
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Outer & Inner loop drawings, TopoJSON
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| path { | |
| fill: none; | |
| stroke-width: 2px; | |
| -webkit-transition: 0.2s; | |
| -moz-transition: 0.2s; | |
| -ms-transition: 0.2s; | |
| -o-transition: 0.2s; | |
| transition: 0.2s; | |
| } | |
| .outer-loop { | |
| stroke: red; | |
| } | |
| .inner-loop { | |
| stroke: steelblue; | |
| } | |
| circle { | |
| fill: orange; | |
| stroke: #fff; | |
| stroke-width: 3px; | |
| } | |
| </style> | |
| <body> | |
| <div id="main"></div> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <script src="http://d3js.org/topojson.v1.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 500; | |
| var projection = d3.geo.albers() | |
| .center([0, 37.7]) | |
| .scale(500); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| d3.json("donut.json", function(error, polygon) { | |
| var data = topojson.feature(polygon, polygon.objects.donut).features[0].geometry.coordinates; | |
| var coordinatesOuter = data[0].map(projection); | |
| var coordinatesInner = data[1].map(projection); | |
| // begin string concat | |
| dOuter = 'M' + coordinatesOuter[0].join(); | |
| dInner = 'M' + coordinatesInner[0].join(); | |
| pathOuter = svg.append('path').attr('d', dOuter); | |
| pathInner = svg.append('path').attr('d', dInner); | |
| var count = 0; | |
| // start outer loop | |
| loopOuter(); | |
| function loopOuter() { | |
| dOuter += 'L' + coordinatesOuter[count].join(); | |
| pathOuter.attr("d", dOuter) | |
| .attr('class', 'outer-loop') | |
| .transition() | |
| .duration(10) | |
| .attr("d", dOuter) | |
| .each("end", function(){ | |
| count++; | |
| if (count < coordinatesOuter.length) loopOuter(); | |
| else loopInner(); // run inner loop when outer loop finishes | |
| }); | |
| } | |
| var innerCount = 0; | |
| function loopInner() { | |
| console.log(pathInner.transition()); | |
| dInner += 'L' + coordinatesInner[innerCount].join(); | |
| pathInner.attr("d", dInner) | |
| .attr('class', 'inner-loop') | |
| .transition() | |
| .duration(100) | |
| .attr('d', dInner) | |
| .each('end', function(){ | |
| innerCount++; | |
| if (innerCount < coordinatesInner.length) loopInner(); | |
| }); | |
| } | |
| }); | |
| </script> |
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