Engineer at Mapbox, creator of Leaflet, algorithms geek, open source enthusiast, musician, father of twin girls, Ukrainian. 🇺🇦
{
const ratio = Math.min(2.5, width / tin.width), ctx = DOM.context2d(tin.width * ratio, tin.height * ratio);
await visibility();
const T = new Uint8Array(tin.triangles.length / 3); // lookup table for visited triangles
const V = new Uint8Array(tin.coords.length / 2); // lookup table for visited vertices
let numVisited = 0;
for (let i = 0; i < tin.halfedges.length; i++) { // mark all boundary vertices as visited
if (tin.halfedges[i] === -1) V[tin.triangles[i]] = 1;
}
const queue = [];
let h = startingHalfedge; // start with an arbitrary half-edge
while (h !== undefined) {
const h0 = h % 3 === 0 ? h + 2 : h - 1; // previous half-edge in a triangle
const h1 = h % 3 === 2 ? h - 2 : h + 1; // next half-edge in a triangle
const v = tin.triangles[h0]; // tip of the triangle
const l = tin.halfedges[h0]; // half-edge of an adjacent triangle on the left
const r = tin.halfedges[h1]; // half-edge of an adjacent triangle on the right
const t = Math.floor(h / 3); // triangle index
const tipVisited = V[v];
const leftVisited = l === -1 || T[Math.floor(l / 3)];
const rightVisited = r === -1 || T[Math.floor(r / 3)];
T[t] = 1; V[v] = 1; V[tin.triangles[h]] = 1; V[tin.triangles[h1]] = 1; // mark triangle as visited
let type;
if (!tipVisited) {
type = 0; h = r; // C (vertex not yet encoded; add it & continue to the right)
} else if (leftVisited && rightVisited) {
type = 2; h = queue.pop(); // E (dead end; pop from the stack)
} else if (leftVisited) {
type = 1; h = r; // L (left triangle already encoded; continue to the right)
} else if (rightVisited) {
type = 3; h = l; // R (right triangle already encoded; continue to the left)
} else {
type = 4; h = r; queue.push(l); // S (split; continue to the right + add left to the stack)
}
drawTriangle(ctx, t, ++numVisited, type, ratio); if (numVisited % speed === 0) yield ctx.canvas;
}
return ctx.canvas;
}
import {fetchImage} from '@mbostock/cross-origin-images'
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