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Dudeney’s hinged triangle-square
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| <!DOCTYPE html> | |
| <script src="http://d3js.org/d3.v3.min.js" charset="utf-8"></script> | |
| <style> | |
| div { width: 800px; height: 500px; margin: auto; } | |
| svg { width: 100%; height: 100%; stroke-width: 0.01; stroke: white; fill: #4485B6; } | |
| </style> | |
| <div></div> | |
| <script> | |
| function point_to_string(point, origin) { | |
| if (typeof origin == "undefined") origin = [0, 0]; | |
| return (point[0] - origin[0]) + "," + (point[1] - origin[1]); | |
| } | |
| function points_to_string(points, origin) { | |
| return points.map(function(point) { return point_to_string(point, origin); }).join(" "); | |
| } | |
| // http://www.public.asu.edu/~aaafp/hinged/Dudeneytrianglesquare.html | |
| var root_3 = Math.sqrt(3), | |
| p = (3 - Math.sqrt(4*root_3 - 3))/4, | |
| np = 3/4 - p, | |
| i = ( (1/4 - p) * np + 3/16 ) / ( np*np + 3/16 ), | |
| e = [ p + i*np, i * root_3/4 ], | |
| j = ( (1/2) * np ) / ( np*np + 3/16 ), | |
| c = [ p + j*np, j * root_3/4 ]; | |
| var svg = d3.select("div").append("svg").attr("viewBox", "-1 -0.6 3 2"), | |
| outer = svg.append("g").attr("transform", "translate(0,0)"); | |
| outer.append("polygon").attr("id", "a").attr("points", points_to_string([ | |
| [1/2, root_3/2], [3/4, root_3/4], e, [1/4, root_3/4] ])); | |
| function polygon(name, points, within, outer_origin) { | |
| if (typeof within == "undefined") within = outer; | |
| var origin = points[0], translation = [origin[0], origin[1]]; | |
| if (typeof outer_origin != "undefined") { | |
| translation[0] -= outer_origin[0]; | |
| translation[1] -= outer_origin[1]; | |
| } | |
| var g = within.append("g").attr("id", name) | |
| .attr("transform", "translate("+point_to_string(translation)+")") | |
| .append("g").attr("class", "rotatethis").attr("transform", "rotate(0)"); | |
| g.append("polygon").attr("points", points_to_string(points, origin)); | |
| return function(name, points) { | |
| return polygon(name, points, g, origin); | |
| }; | |
| } | |
| polygon("b", [ [1/4, root_3/4], e, [p, 0], [0, 0] ]) | |
| ("c", [ [p, 0], c, [p+1/2, 0] ]); | |
| polygon("d", [ [3/4, root_3/4], [1, 0], [p+1/2, 0], c ]); | |
| var duration = 3000, | |
| transforms = { | |
| triangle: "translate(0,0) rotate(0,0.5,0.5)", | |
| square: "translate(0,-0.3) rotate(49,0.5,0.5)" | |
| }; | |
| function toSquare() { | |
| outer.transition().duration(duration).attrTween("transform", function() { | |
| return d3.interpolateString(transforms.triangle, transforms.square); | |
| }); | |
| svg.selectAll("#b, #c").selectAll(".rotatethis").transition().duration(duration).attr("transform", "rotate(-180)"); | |
| svg.selectAll("#d").selectAll(".rotatethis").transition().duration(duration).attr("transform", "rotate(180)"); | |
| } | |
| function toTriangle() { | |
| outer.transition().duration(duration).attrTween("transform", function() { | |
| return d3.interpolateString(transforms.square, transforms.triangle); | |
| }); | |
| svg.selectAll("#b, #c, #d").selectAll(".rotatethis").transition().duration(duration).attr("transform", "rotate(0)"); | |
| } | |
| var triangle = true; | |
| function flip() { | |
| if (triangle) toSquare(); | |
| else toTriangle(); | |
| triangle = !triangle; | |
| } | |
| setInterval(flip, duration + 500); | |
| flip(); | |
| </script> |
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