optimise and test sphere2.collisionArea

axelpale · Oct 15, 2023 · b296a15 · b296a15
1 parent 37cf07d
commit b296a15
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diff --git a/lib/sphere2/collisionArea.js b/lib/sphere2/collisionArea.js
@@ -37,6 +37,11 @@ module.exports = (c, cc) => {
     return Math.PI * rr2
   }
 
+  if (d > r + rr) {
+    // Circles too distant. Just for optimization.
+    return 0
+  }
+
   const area = r2 * Math.acos((d2 + r2 - rr2) / (2 * d * r)) +
     rr2 * Math.acos((d2 + rr2 - r2) / (2 * d * rr)) -
     0.5 * Math.sqrt((-d + r + rr) * (d + r - rr) * (d - r + rr) * (d + r + rr))

diff --git a/test/sphere2/collisionArea.test.js b/test/sphere2/collisionArea.test.js
@@ -14,6 +14,12 @@ module.exports = (ts) => {
       'concentric spheres overlap'
     )
 
+    t.equal(
+      sphere2.collisionArea({ x: 0, y: 0, r: 1 }, { x: 1.5, y: 1.5, r: 1 }),
+      0,
+      'spheres too far'
+    )
+
     t.almostEqual(
       sphere2.collisionArea({ x: 0, y: 0, r: 1 }, { x: 1, y: 0, r: 1 }),
       // overlap = 2 * segment