From 9a34ce71ac4ca719ba94c2f5bb36faf483e63b67 Mon Sep 17 00:00:00 2001
From: Richard Davey <rdavey@gmail.com>
Date: Tue, 18 Jul 2017 02:35:55 +0100
Subject: [PATCH] Added Camera Hit Test specific cull

---
 v3/src/camera/Camera.js                 |  1 +
 v3/src/camera/components/CullHitTest.js | 67 +++++++++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100644 v3/src/camera/components/CullHitTest.js

diff --git a/v3/src/camera/Camera.js b/v3/src/camera/Camera.js
index 0116f57d4..fc6a076f1 100644
--- a/v3/src/camera/Camera.js
+++ b/v3/src/camera/Camera.js
@@ -67,6 +67,7 @@ var Camera = new Class({
     centerToBounds: require('./components/CenterToBounds'),
     centerToSize: require('./components/CenterToSize'),
     cull: require('./components/Cull'),
+    cullHitTest: require('./components/CullHitTest'),
     destroy: require('./components/Destroy'),
     fade: require('./components/Fade'),
     flash: require('./components/Flash'),
diff --git a/v3/src/camera/components/CullHitTest.js b/v3/src/camera/components/CullHitTest.js
new file mode 100644
index 000000000..39955ba33
--- /dev/null
+++ b/v3/src/camera/components/CullHitTest.js
@@ -0,0 +1,67 @@
+var CullHitTest = function (interactiveObjects)
+{
+    if (this.disableCull)
+    {
+        return interactiveObjects;
+    }
+
+    var cameraMatrix = this.matrix.matrix;
+
+    var mva = cameraMatrix[0];
+    var mvb = cameraMatrix[1];
+    var mvc = cameraMatrix[2];
+    var mvd = cameraMatrix[3];
+    
+    /* First Invert Matrix */
+    var determinant = (mva * mvd) - (mvb * mvc);
+
+    if (!determinant)
+    {
+        return interactiveObjects;
+    }
+
+    var mve = cameraMatrix[4];
+    var mvf = cameraMatrix[5];
+
+    var scrollX = this.scrollX;
+    var scrollY = this.scrollY;
+    var cameraW = this.width;
+    var cameraH = this.height;
+    var length = interactiveObjects.length;
+
+    determinant = 1 / determinant;
+
+    var culledObjects = [];
+
+    for (var index = 0; index < length; ++index)
+    {
+        var object = interactiveObjects[index].gameObject;
+
+        if (!object.hasOwnProperty('width'))
+        {
+            culledObjects.push(interactiveObjects[index]);
+            continue;
+        }
+
+        var objectW = object.width;
+        var objectH = object.height;
+        var objectX = (object.x - (scrollX * object.scrollFactorX)) - (objectW * object.originX);
+        var objectY = (object.y - (scrollY * object.scrollFactorY)) - (objectH * object.originY);
+        var tx = (objectX * mva + objectY * mvc + mve);
+        var ty = (objectX * mvb + objectY * mvd + mvf);
+        var tw = ((objectX + objectW) * mva + (objectY + objectH) * mvc + mve);
+        var th = ((objectX + objectW) * mvb + (objectY + objectH) * mvd + mvf);
+        var cullW = cameraW + objectW;
+        var cullH = cameraH + objectH;
+
+        if (tx > -objectW || ty > -objectH || tx < cullW || ty < cullH ||
+            tw > -objectW || th > -objectH || tw < cullW || th < cullH)
+        {
+            culledObjects.push(interactiveObjects[index]);
+        }
+    }
+
+    return culledObjects;
+};
+
+module.exports = CullHitTest;