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+'use strict';
+
+import Voronoi from './3rdparty/rhill-voronoi-core.js';
+
+import { useAverage } from './Util.js';
+import { AABB, QuadTree } from './Geometry.js';
+
+
+/* from here on up, we always assume that points live in the range [(0,0), (1,1)) */
+
+function lloydRelax(point_set, density) {
+ /* setup quadtree and averages */
+ let tree = new QuadTree(1,1);
+ let averages = {};
+ for (let i=0; i<point_set.length; i++) {
+ const point = point_set[i];
+ point.index = i;
+ tree.insert(point);
+
+ let [avg, append] = useAverage();
+ const cent_x = { avg, append };
+ [avg, append] = useAverage();
+ const cent_y = { avg, append };
+ averages[i] = { cent_x, cent_y };
+ }
+
+ /* compute average centroids */
+ for (let x=0; x<1; x += 1/density) {
+ for (let y=0; y<1; y += 1/density) {
+ const point = { x, y };
+ const closest = tree.closest(point);
+ const { cent_x, cent_y } = averages[closest.index];
+ cent_x.append(point.x);
+ cent_y.append(point.y);
+ }
+ }
+
+ /* return centroid points */
+ const result = [];
+ for (let i=0; i<point_set.length; i++) {
+ const point = { x: averages[i].cent_x.avg(), y: averages[i].cent_y.avg() };
+ result.push(point);
+ }
+ return result;
+}
+
+
+class Terrain {
+ constructor() {
+ const N_SEED_POINTS = 2**12;
+ const N_RELAX_ITERATIONS = 1;
+ const RELAX_DENSITY = 400;
+ const randomPoint = () => ({x: Math.random(), y: Math.random()});
+
+ this.min_height = 0;
+ this.max_height = 0;
+
+ let seed_points = [];
+ for (let i=0; i<N_SEED_POINTS; i++) seed_points.push(randomPoint());
+
+ for (let i=0; i<N_RELAX_ITERATIONS; i++)
+ lloydRelax(seed_points, RELAX_DENSITY);
+
+ const v = new Voronoi();
+ this.graph = v.compute(seed_points, {xl: 0, xr: 1, yt: 0, yb: 1});
+
+ this.tree = new QuadTree(1,1);
+ for (let v of this.graph.vertices) {
+ v.height = 0;
+ this.tree.insert(v);
+ }
+ }
+
+
+ applyBrush(x, y, f, strength, radius) {
+ const region = new AABB(x-radius, y-radius, 2*radius, 2*radius);
+ const points = this.tree.root.getPointsInRegion(region);
+
+ const dist2 = (a, b) => (a.x - b.x)**2 + (a.y - b.y)**2;
+
+ const sigma = radius/3;
+ const beta = 1/(2*sigma*sigma);
+ const center = { x, y };
+ const power = pt => Math.exp(-beta * dist2(pt, center));
+
+ for (let pt of points) f(pt, strength * power(pt));
+ }
+
+
+ renderGrid(ct) {
+ ct.save();
+ ct.lineWidth = 0.001;
+ for (let edge of this.graph.edges) {
+ ct.fillStyle = `hsl(${edge.va.height}, 100%, 50%)`;
+ ct.beginPath();
+ ct.arc(edge.va.x, edge.va.y, 0.005, 0, 2*Math.PI);
+ ct.closePath();
+ ct.fill();
+
+ ct.beginPath();
+ ct.moveTo(edge.va.x, edge.va.y);
+ ct.lineTo(edge.vb.x, edge.vb.y);
+ ct.closePath();
+ ct.stroke();
+ }
+ ct.restore();
+ }
+}
+
+export { lloydRelax };
+export default Terrain;