Published
Edited
Apr 5, 2022
50 stars
// https://observablehq.com/@fil/chord-area-inverse
chordAreaInverse = x => Math.pow(x, 0.6) - Math.pow(1 - x, 0.6)
function discUniformTransport1(points, radius) {
const n = points.length / 2,
indices = d3.range(n);
const a = 2 * Math.PI * Math.random(),
sa = Math.sin(a),
ca = Math.cos(a);
const projection = Array.from({ length: indices.length });
for (let i = 0; i < projection.length; i++)
projection[i] = ca * points[2 * i] + sa * points[2 * i + 1];
indices.sort((i, j) => projection[i] - projection[j]);
for (let k = 0; k < n; k++) {
const i = indices[k],
ideal = radius * chordAreaInverse((k + 1) / (n + 1)),
delta = ideal - projection[i];
points[2 * i] += ca * delta;
points[2 * i + 1] += sa * delta;
}
}
discUniformTransportBatched = {
let indices = [],
projection,
deltas;
// batched
return (
points,
radius,
{ dirs = 3, strength = 1, profile = chordAreaInverse } = {}
) => {
const n = points.length / 2;
if (n !== indices.length) {
indices = Uint32Array.from(d3.range(n));
projection = new Float32Array(n);
deltas = new Float32Array(2 * n);
}
const a = 2 * Math.PI * Math.random();
deltas.fill(0);
for (let d = 0; d < dirs; d++) {
const ap = a + (Math.PI * d) / dirs,
sa = Math.sin(ap),
ca = Math.cos(ap);
for (let i = 0; i < n; i++)
projection[i] = ca * points[2 * i] + sa * points[2 * i + 1];
indices.sort((i, j) => projection[i] - projection[j]);
for (let k = 0; k < n; k++) {
const i = indices[k],
ideal = radius * profile(k / (n + 1)),
delta = ideal - projection[i];
deltas[2 * i] += ca * delta;
deltas[2 * i + 1] += sa * delta;
}
}
for (let i = 0; i < points.length; i++)
points[i] += (deltas[i] / dirs) * strength;
};
}
function rectangleUniformTransport(points, x, y, { strength = 1 } = {}) {
const n = points.length / 2,
indices = d3.range(n);
const projection = Array.from({ length: indices.length });
// horizontal
for (let i = 0; i < projection.length; i++) projection[i] = points[2 * i];
indices.sort((i, j) => projection[i] - projection[j]);
for (let k = 0; k < n; k++) {
const i = indices[k],
ideal = x * ((k + 1) / (n + 1)),
delta = ideal - projection[i];
points[2 * i] += delta * strength;
}
// vertical
for (let i = 0; i < projection.length; i++) projection[i] = points[2 * i + 1];
indices.sort((i, j) => projection[i] - projection[j]);
for (let k = 0; k < n; k++) {
const i = indices[k],
ideal = y * ((k + 1) / (n + 1)),
delta = ideal - projection[i];
points[2 * i + 1] += delta * strength;
}
}
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