in packages/charts/src/utils/d3-delaunay/index.ts [314:525]
update() {
const { coords, _hullPrev: hullPrev, _hullNext: hullNext, _hullTri: hullTri, _hullHash: hullHash } = this;
const n = coords.length >> 1;
// populate an array of point indices; calculate input data bbox
let minX = Infinity;
let minY = Infinity;
let maxX = -Infinity;
let maxY = -Infinity;
for (let i = 0; i < n; i++) {
const x = coords[2 * i];
const y = coords[2 * i + 1];
if (x < minX) minX = x;
if (y < minY) minY = y;
if (x > maxX) maxX = x;
if (y > maxY) maxY = y;
this._ids[i] = i;
}
const cx = (minX + maxX) / 2;
const cy = (minY + maxY) / 2;
let minDist = Infinity;
let i0, i1, i2;
// pick a seed point close to the center
for (let i = 0; i < n; i++) {
const d = dist(cx, cy, coords[2 * i], coords[2 * i + 1]);
if (d < minDist) {
i0 = i;
minDist = d;
}
}
const i0x = coords[2 * i0];
const i0y = coords[2 * i0 + 1];
minDist = Infinity;
// find the point closest to the seed
for (let i = 0; i < n; i++) {
if (i === i0) continue;
const d = dist(i0x, i0y, coords[2 * i], coords[2 * i + 1]);
if (d < minDist && d > 0) {
i1 = i;
minDist = d;
}
}
let i1x = coords[2 * i1];
let i1y = coords[2 * i1 + 1];
let minRadius = Infinity;
// find the third point which forms the smallest circumcircle with the first two
for (let i = 0; i < n; i++) {
if (i === i0 || i === i1) continue;
const r = circumradius(i0x, i0y, i1x, i1y, coords[2 * i], coords[2 * i + 1]);
if (r < minRadius) {
i2 = i;
minRadius = r;
}
}
let i2x = coords[2 * i2];
let i2y = coords[2 * i2 + 1];
if (minRadius === Infinity) {
// order collinear points by dx (or dy if all x are identical)
// and return the list as a hull
for (let i = 0; i < n; i++) {
this._dists[i] = coords[2 * i] - coords[0] || coords[2 * i + 1] - coords[1];
}
quicksort(this._ids, this._dists, 0, n - 1);
const hull = new Uint32Array(n);
let j = 0;
for (let i = 0, d0 = -Infinity; i < n; i++) {
const id = this._ids[i];
if (this._dists[id] > d0) {
hull[j++] = id;
d0 = this._dists[id];
}
}
this.hull = hull.subarray(0, j);
this.triangles = new Uint32Array(0);
this.halfedges = new Uint32Array(0);
return;
}
// swap the order of the seed points for counter-clockwise orientation
if (orient(i0x, i0y, i1x, i1y, i2x, i2y)) {
const i = i1;
const x = i1x;
const y = i1y;
i1 = i2;
i1x = i2x;
i1y = i2y;
i2 = i;
i2x = x;
i2y = y;
}
const center = circumcenter(i0x, i0y, i1x, i1y, i2x, i2y);
this._cx = center.x;
this._cy = center.y;
for (let i = 0; i < n; i++) {
this._dists[i] = dist(coords[2 * i], coords[2 * i + 1], center.x, center.y);
}
// sort the points by distance from the seed triangle circumcenter
quicksort(this._ids, this._dists, 0, n - 1);
// set up the seed triangle as the starting hull
this._hullStart = i0;
let hullSize = 3;
hullNext[i0] = hullPrev[i2] = i1;
hullNext[i1] = hullPrev[i0] = i2;
hullNext[i2] = hullPrev[i1] = i0;
hullTri[i0] = 0;
hullTri[i1] = 1;
hullTri[i2] = 2;
hullHash.fill(-1);
hullHash[this._hashKey(i0x, i0y)] = i0;
hullHash[this._hashKey(i1x, i1y)] = i1;
hullHash[this._hashKey(i2x, i2y)] = i2;
this.trianglesLen = 0;
this._addTriangle(i0, i1, i2, -1, -1, -1);
for (let k = 0, xp, yp; k < this._ids.length; k++) {
const i = this._ids[k];
const x = coords[2 * i];
const y = coords[2 * i + 1];
// skip near-duplicate points
if (k > 0 && Math.abs(x - xp) <= EPSILON && Math.abs(y - yp) <= EPSILON) continue;
xp = x;
yp = y;
// skip seed triangle points
if (i === i0 || i === i1 || i === i2) continue;
// find a visible edge on the convex hull using edge hash
let start = 0;
for (let j = 0, key = this._hashKey(x, y); j < this._hashSize; j++) {
start = hullHash[(key + j) % this._hashSize];
if (start !== -1 && start !== hullNext[start]) break;
}
start = hullPrev[start];
let e = start,
q;
while (((q = hullNext[e]), !orient(x, y, coords[2 * e], coords[2 * e + 1], coords[2 * q], coords[2 * q + 1]))) {
e = q;
if (e === start) {
e = -1;
break;
}
}
if (e === -1) continue; // likely a near-duplicate point; skip it
// add the first triangle from the point
let t = this._addTriangle(e, i, hullNext[e], -1, -1, hullTri[e]);
// recursively flip triangles from the point until they satisfy the Delaunay condition
hullTri[i] = this._legalize(t + 2);
hullTri[e] = t; // keep track of boundary triangles on the hull
hullSize++;
// walk forward through the hull, adding more triangles and flipping recursively
let n = hullNext[e];
while (((q = hullNext[n]), orient(x, y, coords[2 * n], coords[2 * n + 1], coords[2 * q], coords[2 * q + 1]))) {
t = this._addTriangle(n, i, q, hullTri[i], -1, hullTri[n]);
hullTri[i] = this._legalize(t + 2);
hullNext[n] = n; // mark as removed
hullSize--;
n = q;
}
// walk backward from the other side, adding more triangles and flipping
if (e === start) {
while (((q = hullPrev[e]), orient(x, y, coords[2 * q], coords[2 * q + 1], coords[2 * e], coords[2 * e + 1]))) {
t = this._addTriangle(q, i, e, -1, hullTri[e], hullTri[q]);
this._legalize(t + 2);
hullTri[q] = t;
hullNext[e] = e; // mark as removed
hullSize--;
e = q;
}
}
// update the hull indices
this._hullStart = hullPrev[i] = e;
hullNext[e] = hullPrev[n] = i;
hullNext[i] = n;
// save the two new edges in the hash table
hullHash[this._hashKey(x, y)] = i;
hullHash[this._hashKey(coords[2 * e], coords[2 * e + 1])] = e;
}
this.hull = new Uint32Array(hullSize);
for (let i = 0, e = this._hullStart; i < hullSize; i++) {
this.hull[i] = e;
e = hullNext[e];
}
// trim typed triangle mesh arrays
this.triangles = this._triangles.subarray(0, this.trianglesLen);
this.halfedges = this._halfedges.subarray(0, this.trianglesLen);
}