Minor update - frustum rework

Complete overhaul of frustum culling

enginecustom/frustum.h

@@ -0,0 +1,12 @@
+#include <DirectXMath.h>
+using namespace DirectX;
+
+class Frustum
+{
+public:
+    void ConstructFrustum(float screenDepth, XMMATRIX projectionMatrix, XMMATRIX viewMatrix);
+    bool CheckCube(float xCenter, float yCenter, float zCenter, float radius, float tolerance);
+
+private:
+    XMVECTOR m_planes[6];
+};