Given an angle and a radius, calculate a point's cartesian coordinates. See this StackExchange answer.
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November 30, 2018 14:23
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Cartesian Points In A Circle
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| license: gpl-3.0 |
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> | |
| <style> | |
| body { | |
| margin: 0 auto; | |
| display: table; | |
| } | |
| text { | |
| text-anchor: middle; | |
| font-family: "Helvetica Neue", sans-serif; | |
| } | |
| .outline { | |
| fill: none; | |
| stroke: black; | |
| stroke-width: 2px; | |
| } | |
| .center { | |
| fill: tomato; | |
| } | |
| .circle { | |
| stroke-width: 2px; | |
| fill: none; | |
| } | |
| .line { | |
| stroke-width: 2px; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <script src="https://d3js.org/d3.v5.min.js"></script> | |
| <script src="https://unpkg.com/geometric@0.0.6/build/geometric.js"></script> | |
| <script> | |
| var radius, | |
| margin = 2, | |
| dot_radius = 3, | |
| center_radius = 30, | |
| circles_data = []; | |
| var svg = d3.select("body").append("svg"); | |
| var g = svg.append("g") | |
| .attr("transform", "translate(" + margin + ", " + margin + ")"); | |
| var outline = g.append("circle") | |
| .attr("class", "outline"); | |
| var center = g.append("circle") | |
| .attr("class", "center") | |
| .attr("r", center_radius); | |
| var text = g.append("text").attr("dy", 5); | |
| window.onload = _ => { | |
| resize(); | |
| makeNewCircle(); | |
| redraw(); | |
| d3.interval(_ => { | |
| makeNewCircle(); | |
| redraw(); | |
| }, 500); | |
| window.onresize = resize; | |
| }; | |
| function resize(){ | |
| radius = Math.min(window.innerWidth, window.innerHeight) - margin * 2; | |
| d3.select("div").style("left", (window.innerWidth / 2) + "px").style("top", (radius / 2) + "px"); | |
| text.attr("x", radius / 2).attr("y", radius / 2) | |
| svg.attr("width", radius + margin * 2).attr("height", radius + margin * 2); | |
| outline | |
| .attr("r", radius / 2) | |
| .attr("cx", radius / 2) | |
| .attr("cy", radius / 2); | |
| center | |
| .attr("cx", radius / 2) | |
| .attr("cy", radius / 2); | |
| // Recalculate current points based on new radius. | |
| circles_data.forEach(d => { | |
| d.coordinates = geometric.translateDegrees([radius / 2, radius / 2], d.angle, d.distance_pct * radius / 200); | |
| return d; | |
| }); | |
| redraw(); | |
| } | |
| function redraw(){ | |
| var circles = g.selectAll(".circle") | |
| .data(circles_data, d => d.id); | |
| var lines = g.selectAll(".line") | |
| .data(circles_data, d => d.id); | |
| var dots = g.selectAll(".dot") | |
| .data(circles_data, d => d.id); | |
| circles | |
| .attr("cx", radius / 2) | |
| .attr("cy", radius / 2) | |
| .attr("r", d => radius * d.distance_pct / 200) | |
| .transition() | |
| .style("stroke", "#ccc") | |
| .style("opacity", .1); | |
| lines | |
| .attr("x1", radius / 2) | |
| .attr("y1", radius / 2) | |
| .attr("x2", d => d.coordinates[0]) | |
| .attr("y2", d => d.coordinates[1]) | |
| .transition() | |
| .style("opacity", .1); | |
| dots | |
| .attr("cx", d => d.coordinates[0]) | |
| .attr("cy", d => d.coordinates[1]) | |
| .transition() | |
| .style("opacity", .8); | |
| circles.enter().append("circle") | |
| .attr("class", "circle") | |
| .attr("r", d => radius * d.distance_pct / 200) | |
| .attr("cx", radius / 2) | |
| .attr("cy", radius / 2) | |
| .style("stroke", "steelblue") | |
| .style("opacity", 1e-6) | |
| .transition() | |
| .duration(250) | |
| .style("opacity", 1); | |
| lines.enter().append("line") | |
| .attr("class", "line") | |
| .attr("x1", radius / 2) | |
| .attr("y1", radius / 2) | |
| .attr("x2", radius / 2) | |
| .attr("y2", radius / 2) | |
| .style("stroke", "steelblue") | |
| .transition() | |
| .delay(125) | |
| .duration(250) | |
| .attr("x2", d => d.coordinates[0]) | |
| .attr("y2", d => d.coordinates[1]); | |
| dots.enter().append("circle") | |
| .attr("class", "dot") | |
| .attr("r", dot_radius) | |
| .attr("cx", d => d.coordinates[0]) | |
| .attr("cy", d => d.coordinates[1]) | |
| .attr("opacity", 1e-6) | |
| .transition() | |
| .delay(250) | |
| .duration(500) | |
| .attr("opacity", 1); | |
| center.raise(); | |
| text.raise(); | |
| } | |
| function makeNewCircle(distance, angle){ | |
| var new_obj = { | |
| distance_pct: Math.max((center_radius + dot_radius * 2) / radius * 100, randomPercent()), | |
| angle: randomAngle(), | |
| id: circles_data.length | |
| }; | |
| text.text(new_obj.angle); | |
| new_obj.coordinates = geometric.translateDegrees([radius / 2, radius / 2], new_obj.angle, new_obj.distance_pct * radius / 200) | |
| circles_data.push(new_obj); | |
| } | |
| function randomPercent(){ | |
| return randomBetween(0, 100); | |
| } | |
| function randomAngle(){ | |
| return randomBetween(0, 360); | |
| } | |
| function randomBetween(min, max){ | |
| return Math.floor(Math.random() * (max - min + 1) + min); | |
| } | |
| </script> | |
| </body> | |
| </html> |
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