Randomly placed actors explore a 2d function by walking along contour lines. Perlin noise courtesy of d2fn.
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June 14, 2020 13:30
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Randomized Contour Lines
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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 src="/d2fn/raw/8777d620caef32959713/perlin.js"></script> | |
| <script> | |
| var TWO_PI = Math.PI * 2, | |
| PI_OVER_TWO = Math.PI / 2, | |
| INFINITY = 1 / 0; | |
| var width = 960, | |
| height = 500, | |
| noiseScale = 0.003, | |
| numContours = 200, | |
| step = 0, | |
| steps = 5000, | |
| stepLength = 0.5, | |
| turnAngle = TWO_PI / 32; | |
| var context = setupCanvas(width, height), | |
| noise = perlin.noise(noiseScale), | |
| easing = easeAlpha(steps); | |
| var contours = []; | |
| for (var i = 0; i < numContours; i++) { | |
| contours.push(randomContour(width, height, noise, stepLength, turnAngle)); | |
| } | |
| d3.timer(function() { | |
| if (++step > steps) { | |
| console.log("done with animation"); | |
| return true; | |
| } | |
| context.lineWidth = 1; | |
| context.globalCompositeOperation = 'lighter'; | |
| context.beginPath(); | |
| var alpha = easing.get(); | |
| contours.forEach(function(contour) { | |
| var ln = contour.step(); | |
| context.strokeStyle = "rgba(49, 130, 189," + alpha + ")"; | |
| context.moveTo(ln.x1, ln.y1); | |
| context.lineTo(ln.x2, ln.y2); | |
| }); | |
| context.stroke(); | |
| easing.step(); | |
| }) | |
| // Append a (width x height) canvas element to the body and return its context | |
| // object. | |
| function setupCanvas(width, height) { | |
| var canvas = d3.select("body") | |
| .append("canvas") | |
| .attr({width: width, height: height}); | |
| var context = canvas.node().getContext("2d"); | |
| context.fillStyle = "rgb(0, 0, 0)"; | |
| context.fillRect(-1, -1, width, height); | |
| return context; | |
| } | |
| // An object that eases opacity as steps progress. | |
| function easeAlpha(steps) { | |
| var n = 0, alpha = 0; | |
| return { | |
| step: function() { alpha = 0.3 + 0.125 * (1 - Math.cos(2 * Math.PI * (n++ / steps))) }, | |
| get: function() { return alpha } | |
| } | |
| } | |
| // Returns an object with a step() method that walks in 2d space while trying | |
| // to keep f(x, y) as close to f(x_start, y_start) as possible. The object only | |
| // walks "forward" - objects maintain a current heading, and only look for new | |
| // points in a +/- 90 arc. | |
| function randomContour(width, height, f, stepLength, turnAngle, minimumStep) { | |
| var x = Math.random() * width, | |
| y = Math.random() * height, | |
| heading = Math.random() * TWO_PI, | |
| currentValue = f(x, y); | |
| return { | |
| step: function() { | |
| var x1 = x, y1 = y; | |
| var minDelta = INFINITY, | |
| minHeading = heading, | |
| minF = -1, | |
| minX = -1, | |
| minY = -1; | |
| for (var theta = heading - PI_OVER_TWO; theta < heading + PI_OVER_TWO; theta += turnAngle) { | |
| var newX = x + stepLength * Math.cos(theta), | |
| newY = y + stepLength * Math.sin(theta), | |
| newValue = f(newX, newY), | |
| delta = Math.abs(newValue - currentValue); | |
| if (delta < minDelta) { | |
| minDelta = delta; | |
| minHeading = theta; | |
| minF = newValue; | |
| minX = newX; | |
| minY = newY; | |
| } | |
| } | |
| x = minX; | |
| y = minY; | |
| heading = minHeading; | |
| currentValue = minF; | |
| return {x1: x1, y1: y1, x2: x, y2: y} | |
| } | |
| } | |
| } | |
| </script> | |
| </body> |
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