mirror of
https://github.com/seigler/generative
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237 lines
7 KiB
JavaScript
237 lines
7 KiB
JavaScript
// from https://github.com/ironwallaby/delaunay
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var Delaunay;
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(function() {
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"use strict";
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var EPSILON = 1.0 / 1048576.0;
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function supertriangle(vertices) {
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var xmin = Number.POSITIVE_INFINITY,
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ymin = Number.POSITIVE_INFINITY,
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xmax = Number.NEGATIVE_INFINITY,
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ymax = Number.NEGATIVE_INFINITY,
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i, dx, dy, dmax, xmid, ymid;
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for(i = vertices.length; i--; ) {
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if(vertices[i][0] < xmin) xmin = vertices[i][0];
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if(vertices[i][0] > xmax) xmax = vertices[i][0];
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if(vertices[i][1] < ymin) ymin = vertices[i][1];
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if(vertices[i][1] > ymax) ymax = vertices[i][1];
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}
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dx = xmax - xmin;
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dy = ymax - ymin;
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dmax = Math.max(dx, dy);
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xmid = xmin + dx * 0.5;
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ymid = ymin + dy * 0.5;
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return [
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[xmid - 20 * dmax, ymid - dmax],
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[xmid , ymid + 20 * dmax],
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[xmid + 20 * dmax, ymid - dmax]
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];
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}
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function circumcircle(vertices, i, j, k) {
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var x1 = vertices[i][0],
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y1 = vertices[i][1],
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x2 = vertices[j][0],
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y2 = vertices[j][1],
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x3 = vertices[k][0],
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y3 = vertices[k][1],
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fabsy1y2 = Math.abs(y1 - y2),
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fabsy2y3 = Math.abs(y2 - y3),
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xc, yc, m1, m2, mx1, mx2, my1, my2, dx, dy;
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/* Check for coincident points */
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if(fabsy1y2 < EPSILON && fabsy2y3 < EPSILON)
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throw new Error("Eek! Coincident points!");
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if(fabsy1y2 < EPSILON) {
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m2 = -((x3 - x2) / (y3 - y2));
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mx2 = (x2 + x3) / 2.0;
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my2 = (y2 + y3) / 2.0;
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xc = (x2 + x1) / 2.0;
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yc = m2 * (xc - mx2) + my2;
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}
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else if(fabsy2y3 < EPSILON) {
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m1 = -((x2 - x1) / (y2 - y1));
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mx1 = (x1 + x2) / 2.0;
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my1 = (y1 + y2) / 2.0;
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xc = (x3 + x2) / 2.0;
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yc = m1 * (xc - mx1) + my1;
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}
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else {
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m1 = -((x2 - x1) / (y2 - y1));
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m2 = -((x3 - x2) / (y3 - y2));
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mx1 = (x1 + x2) / 2.0;
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mx2 = (x2 + x3) / 2.0;
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my1 = (y1 + y2) / 2.0;
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my2 = (y2 + y3) / 2.0;
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xc = (m1 * mx1 - m2 * mx2 + my2 - my1) / (m1 - m2);
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yc = (fabsy1y2 > fabsy2y3) ?
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m1 * (xc - mx1) + my1 :
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m2 * (xc - mx2) + my2;
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}
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dx = x2 - xc;
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dy = y2 - yc;
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return {i: i, j: j, k: k, x: xc, y: yc, r: dx * dx + dy * dy};
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}
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function dedup(edges) {
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var i, j, a, b, m, n;
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for(j = edges.length; j; ) {
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b = edges[--j];
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a = edges[--j];
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for(i = j; i; ) {
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n = edges[--i];
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m = edges[--i];
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if((a === m && b === n) || (a === n && b === m)) {
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edges.splice(j, 2);
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edges.splice(i, 2);
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break;
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}
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}
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}
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}
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Delaunay = {
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triangulate: function(vertices, key) {
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var n = vertices.length,
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i, j, indices, st, open, closed, edges, dx, dy, a, b, c;
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/* Bail if there aren't enough vertices to form any triangles. */
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if(n < 3)
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return [];
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/* Slice out the actual vertices from the passed objects. (Duplicate the
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* array even if we don't, though, since we need to make a supertriangle
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* later on!) */
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vertices = vertices.slice(0);
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if(key)
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for(i = n; i--; )
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vertices[i] = vertices[i][key];
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/* Make an array of indices into the vertex array, sorted by the
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* vertices' x-position. Force stable sorting by comparing indices if
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* the x-positions are equal. */
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indices = new Array(n);
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for(i = n; i--; )
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indices[i] = i;
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indices.sort(function(i, j) {
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var diff = vertices[j][0] - vertices[i][0];
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return diff !== 0 ? diff : i - j;
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});
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/* Next, find the vertices of the supertriangle (which contains all other
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* triangles), and append them onto the end of a (copy of) the vertex
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* array. */
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st = supertriangle(vertices);
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vertices.push(st[0], st[1], st[2]);
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/* Initialize the open list (containing the supertriangle and nothing
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* else) and the closed list (which is empty since we havn't processed
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* any triangles yet). */
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open = [circumcircle(vertices, n + 0, n + 1, n + 2)];
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closed = [];
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edges = [];
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/* Incrementally add each vertex to the mesh. */
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for(i = indices.length; i--; edges.length = 0) {
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c = indices[i];
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/* For each open triangle, check to see if the current point is
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* inside it's circumcircle. If it is, remove the triangle and add
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* it's edges to an edge list. */
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for(j = open.length; j--; ) {
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/* If this point is to the right of this triangle's circumcircle,
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* then this triangle should never get checked again. Remove it
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* from the open list, add it to the closed list, and skip. */
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dx = vertices[c][0] - open[j].x;
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if(dx > 0.0 && dx * dx > open[j].r) {
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closed.push(open[j]);
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open.splice(j, 1);
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continue;
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}
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/* If we're outside the circumcircle, skip this triangle. */
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dy = vertices[c][1] - open[j].y;
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if(dx * dx + dy * dy - open[j].r > EPSILON)
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continue;
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/* Remove the triangle and add it's edges to the edge list. */
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edges.push(
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open[j].i, open[j].j,
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open[j].j, open[j].k,
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open[j].k, open[j].i
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);
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open.splice(j, 1);
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}
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/* Remove any doubled edges. */
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dedup(edges);
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/* Add a new triangle for each edge. */
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for(j = edges.length; j; ) {
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b = edges[--j];
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a = edges[--j];
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open.push(circumcircle(vertices, a, b, c));
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}
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}
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/* Copy any remaining open triangles to the closed list, and then
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* remove any triangles that share a vertex with the supertriangle,
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* building a list of triplets that represent triangles. */
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for(i = open.length; i--; )
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closed.push(open[i]);
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open.length = 0;
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for(i = closed.length; i--; )
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if(closed[i].i < n && closed[i].j < n && closed[i].k < n)
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open.push(closed[i].i, closed[i].j, closed[i].k);
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/* Yay, we're done! */
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return open;
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},
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contains: function(tri, p) {
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/* Bounding box test first, for quick rejections. */
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if((p[0] < tri[0][0] && p[0] < tri[1][0] && p[0] < tri[2][0]) ||
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(p[0] > tri[0][0] && p[0] > tri[1][0] && p[0] > tri[2][0]) ||
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(p[1] < tri[0][1] && p[1] < tri[1][1] && p[1] < tri[2][1]) ||
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(p[1] > tri[0][1] && p[1] > tri[1][1] && p[1] > tri[2][1]))
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return null;
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var a = tri[1][0] - tri[0][0],
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b = tri[2][0] - tri[0][0],
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c = tri[1][1] - tri[0][1],
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d = tri[2][1] - tri[0][1],
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i = a * d - b * c;
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/* Degenerate tri. */
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if(i === 0.0)
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return null;
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var u = (d * (p[0] - tri[0][0]) - b * (p[1] - tri[0][1])) / i,
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v = (a * (p[1] - tri[0][1]) - c * (p[0] - tri[0][0])) / i;
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/* If we're outside the tri, fail. */
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if(u < 0.0 || v < 0.0 || (u + v) > 1.0)
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return null;
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return [u, v];
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}
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};
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if(typeof module !== "undefined")
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module.exports = Delaunay;
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})();
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