A simple reference for me to remember the trigonometry methods required to draw a given shape between two points. In this case it’s an arrow drawn from the centre of the canvas to wherever the mouse cursor is.
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June 28, 2016 11:41
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Draw an arrow between two points
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| license: cc-by-4.0 |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| body { | |
| font-family: sans-serif; | |
| margin: auto; | |
| position: relative; | |
| width: 960px; | |
| } | |
| .control { | |
| left: 50%; | |
| position: absolute; | |
| top: 2em; | |
| transform: translateX(-50%); | |
| } | |
| .control input { | |
| width: 200px; | |
| } | |
| .dot { | |
| fill: #c30; | |
| } | |
| .path { | |
| fill: #667; | |
| fill-opacity: 0.7; | |
| } | |
| </style> | |
| <body> | |
| <script src="//d3js.org/d3.v3.js"></script> | |
| <label class="control">Radius: <input type="range" min="2" max="20" step="1" value="10"></label> | |
| <script> | |
| var width = 960, | |
| height = 500, | |
| radius = 10; | |
| var cx = width / 2, cy = height / 2; | |
| var svg = d3.select('body').append('svg') | |
| .attr('width', width) | |
| .attr('height', height); | |
| var dot = svg.append('circle') | |
| .attr('class', 'dot') | |
| .attr('cx', cx) | |
| .attr('cy', cy) | |
| .attr('r', radius); | |
| var path = svg.append('path') | |
| .attr('class', 'path'); | |
| function trianglePath(xy) { | |
| var x = xy[0] - cx; | |
| var y = xy[1] - cy; | |
| var dist = Math.sqrt(x * x + y * y); | |
| var angle = Math.atan2(y, x) / Math.PI * 180; | |
| return function () { | |
| this.attr('d', 'M0,0 L' + [ | |
| 0, radius, | |
| dist - radius, radius / 3, | |
| dist - radius, radius, | |
| dist, 0, | |
| dist - radius, -radius, | |
| dist - radius, -radius / 3, | |
| 0, -radius | |
| ] + 'z'); | |
| this.attr('transform', 'translate(' + [cx, cy] + ') rotate(' + angle + ')'); | |
| } | |
| } | |
| d3.select(document).on('mousemove', function () { | |
| path.call(trianglePath(d3.mouse(svg.node()))); | |
| }); | |
| document.querySelector('.control input').addEventListener('input', function (e) { | |
| radius = +this.value; | |
| dot.attr('r', radius); | |
| }, false); | |
| </script> |
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