From b5b86595d9226e0398bf8cd2c56a813fa88bb472 Mon Sep 17 00:00:00 2001
From: Richard Davey <rdavey@gmail.com>
Date: Sun, 1 Jan 2017 14:33:41 +0000
Subject: [PATCH] Circle.isEmpty and Circle Intersection functions.

---
 v3/src/geom/circle/Circle.js                |  5 +++
 v3/src/geom/intersects/CircleVsCircle.js    |  8 +++++
 v3/src/geom/intersects/CircleVsRectangle.js | 36 +++++++++++++++++++++
 3 files changed, 49 insertions(+)
 create mode 100644 v3/src/geom/intersects/CircleVsCircle.js
 create mode 100644 v3/src/geom/intersects/CircleVsRectangle.js

diff --git a/v3/src/geom/circle/Circle.js b/v3/src/geom/circle/Circle.js
index ad9e28411..425eeda94 100644
--- a/v3/src/geom/circle/Circle.js
+++ b/v3/src/geom/circle/Circle.js
@@ -39,6 +39,11 @@ Circle.prototype = {
         this.y = y;
 
         return this;
+    },
+
+    isEmpty: function ()
+    {
+        return (this._radius <= 0);
     }
 
 };
diff --git a/v3/src/geom/intersects/CircleVsCircle.js b/v3/src/geom/intersects/CircleVsCircle.js
new file mode 100644
index 000000000..63149a50f
--- /dev/null
+++ b/v3/src/geom/intersects/CircleVsCircle.js
@@ -0,0 +1,8 @@
+var DistanceBetween = require('../../math/distance/DistanceBetween');
+
+var CircleVsCircle = function (circleA, circleB)
+{
+    return (DistanceBetween(circleA.x, circleA.y, circleB.x, circleB.y) <= (circleA.radius + circleB.radius));
+};
+
+module.exports = CircleVsCircle;
diff --git a/v3/src/geom/intersects/CircleVsRectangle.js b/v3/src/geom/intersects/CircleVsRectangle.js
new file mode 100644
index 000000000..2f7fc4edf
--- /dev/null
+++ b/v3/src/geom/intersects/CircleVsRectangle.js
@@ -0,0 +1,36 @@
+var CircleVsRectangle = function (circle, rectangle)
+{
+    var halfWidth = rectangle.width / 2;
+    var halfHeight = rectangle.height / 2;
+
+    var cx = Math.abs(circle.x - rectangle.x - halfWidth);
+    var xDist = halfWidth + circle.radius;
+
+    if (cx > xDist)
+    {
+        return false;
+    }
+
+    var cy = Math.abs(circle.y - rectangle.y - halfHeight);
+    var yDist = halfHeight + circle.radius;
+
+    if (cy > yDist)
+    {
+        return false;
+    }
+
+    if (cx <= halfWidth || cy <= halfHeight)
+    {
+        return true;
+    }
+
+    var xCornerDist = cx - halfWidth;
+    var yCornerDist = cy - halfHeight;
+    var xCornerDistSq = xCornerDist * xCornerDist;
+    var yCornerDistSq = yCornerDist * yCornerDist;
+    var maxCornerDistSq = circle.radius * circle.radius;
+
+    return xCornerDistSq + yCornerDistSq <= maxCornerDistSq;
+};
+
+module.exports = CircleVsRectangle;