Published
Edited
Feb 17, 2019
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chart = {
const context = DOM.context2d(width, height);
const path = d3.geoPath(projection, context);
for (const value of samples(color.domain(), 200)) {
context.beginPath();
path(contours.contour(grid, value));
context.strokeStyle = color(value);
context.stroke();
yield context.canvas;
}
}
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color = d3.scaleSequential(d3.extent(grid), d3.interpolateGreys)
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q = 3 // The level of detail, e.g., sample every 4 pixels in x and y.
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period = 0.005
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n = Math.ceil(width / q) + 1
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m = Math.ceil(height / q) + 1
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projection = d3.geoIdentity().translate([-q / 2, -q / 2]).scale(q)
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contours = d3.contours().size([n, m])
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grid = {
const grid = new Float64Array(n * m);
for (let j = 0; j < m; ++j) {
for (let i = 0; i < n; ++i) {
grid[j * n + i] = noise.noise(i * period, j * period);
}
}
return grid;
}
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noise = new Noise(3)
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class Noise {
static lerp(t, a, b) {
return a + t * (b - a);
}
static grad2d(i, x, y) {
const v = (i & 1) === 0 ? x : y;
return (i & 2) === 0 ? -v : v;
}
constructor(octaves = 1) {
this.p = new Uint8Array(512);
this.octaves = octaves;
this.init();
}
init() {
for (let i = 0; i < 512; ++i) {
this.p[i] = Math.random() * 256;
}
}
noise2d(x2d, y2d) {
const X = Math.floor(x2d) & 255;
const Y = Math.floor(y2d) & 255;
const x = x2d - Math.floor(x2d);
const y = y2d - Math.floor(y2d);
const fx = (3 - 2 * x) * x * x;
const fy = (3 - 2 * y) * y * y;
const p0 = this.p[X] + Y;
const p1 = this.p[X + 1] + Y;
return Noise.lerp(
fy,
Noise.lerp(
fx,
Noise.grad2d(this.p[p0], x, y),
Noise.grad2d(this.p[p1], x - 1, y)
),
Noise.lerp(
fx,
Noise.grad2d(this.p[p0 + 1], x, y - 1),
Noise.grad2d(this.p[p1 + 1], x - 1, y - 1)
)
);
}
noise(x, y) {
let e = 1,
k = 1,
s = 0;
for (let i = 0; i < this.octaves; ++i) {
e *= 0.5;
s += e * (1 + this.noise2d(k * x, k * y)) / 2;
k *= 2;
}
return s;
}
}
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height = 600
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d3 = require("d3@5")
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import {samples} from "@mbostock/1d-poisson-disk-sampling"
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