Fixed a problem with big numbers in packEnclose

Author: w8r

src/pack/enclose.js

@@ -8,16 +8,28 @@ export default function(circles) {
 export function packEncloseRandom(circles, random) {
   var i = 0, n = (circles = shuffle(Array.from(circles), random)).length, B = [], p, e;
 
+  var minX = Number.MAX_VALUE, minY = Number.MAX_VALUE;
+  var maxX = Number.MIN_VALUE, maxY = Number.MIN_VALUE;
+  for (var k = 0; k < n; ++k) {
+    var c = circles[k];
+    minX = Math.min(minX, c.x - c.r);
+    minY = Math.min(minY, c.y - c.r);
+    maxX = Math.max(maxX, c.x + c.r);
+    maxY = Math.max(maxY, c.y + c.r);
+  }
+
+  var cx = (minX + maxX) / 2, cy = (minY + maxY) / 2;
+
   while (i < n) {
     p = circles[i];
     if (e && enclosesWeak(e, p)) ++i;
-    else e = encloseBasis(B = extendBasis(B, p)), i = 0;
+    else e = encloseBasis(B = extendBasis(B, p, cx, cy), cx, cy), i = 0;
   }
 
   return e;
 }
 
-function extendBasis(B, p) {
+function extendBasis(B, p, cx, cy) {
   var i, j;
 
   if (enclosesWeakAll(p, B)) return [p];
@@ -36,7 +48,7 @@ function extendBasis(B, p) {
       if (enclosesNot(encloseBasis2(B[i], B[j]), p)
           && enclosesNot(encloseBasis2(B[i], p), B[j])
           && enclosesNot(encloseBasis2(B[j], p), B[i])
-          && enclosesWeakAll(encloseBasis3(B[i], B[j], p), B)) {
+          && enclosesWeakAll(encloseBasis3(B[i], B[j], p, cx, cy), B)) {
         return [B[i], B[j], p];
       }
     }
@@ -65,11 +77,11 @@ function enclosesWeakAll(a, B) {
   return true;
 }
 
-function encloseBasis(B) {
+function encloseBasis(B, cx, cy) {
   switch (B.length) {
     case 1: return encloseBasis1(B[0]);
     case 2: return encloseBasis2(B[0], B[1]);
-    case 3: return encloseBasis3(B[0], B[1], B[2]);
+    case 3: return encloseBasis3(B[0], B[1], B[2], cx, cy);
   }
 }
 
@@ -93,10 +105,10 @@ function encloseBasis2(a, b) {
   };
 }
 
-function encloseBasis3(a, b, c) {
-  var x1 = a.x, y1 = a.y, r1 = a.r,
-      x2 = b.x, y2 = b.y, r2 = b.r,
-      x3 = c.x, y3 = c.y, r3 = c.r,
+function encloseBasis3(a, b, c, cx, cy) {
+  var x1 = a.x - cx, y1 = a.y - cy, r1 = a.r,
+      x2 = b.x - cx, y2 = b.y - cy, r2 = b.r,
+      x3 = c.x - cx, y3 = c.y - cy, r3 = c.r,
       a2 = x1 - x2,
       a3 = x1 - x3,
       b2 = y1 - y2,
@@ -116,8 +128,8 @@ function encloseBasis3(a, b, c) {
       C = xa * xa + ya * ya - r1 * r1,
       r = -(Math.abs(A) > 1e-6 ? (B + Math.sqrt(B * B - 4 * A * C)) / (2 * A) : C / B);
   return {
-    x: x1 + xa + xb * r,
-    y: y1 + ya + yb * r,
+    x: cx + x1 + xa + xb * r,
+    y: cy + y1 + ya + yb * r,
     r: r
   };
 }

test/pack/enclose-test.js

@@ -10,9 +10,18 @@ it("packEnclose(circles) handles a tricky case", () => {
       {x: 15.5, y: 73.5, r: 8.585}
     ]),
     {
-      r: 20.790781637717107,
-      x: 12.80193548387092,
+      r: 20.790781637717117,
+      x: 12.80193548387097,
       y: 61.59615384615385
     }
   );
 });
+
+it('packEnclose(circles) handles big numbers', () => {
+  const circles = [
+    { "x": 531214.7271532917, "y": 360738.8204573899, "r": 10 },
+    { "x": 531242.0429781883, "y": 360764.87727581244, "r": 10 },
+    { "x": 531239.7927335791, "y": 360716.54336245544, "r": 10 }
+  ];
+  assert.doesNotThrow(() => packEnclose(circles));
+});