From 559946f2fcb276741ccc8e9196a8ce877d9f4d21 Mon Sep 17 00:00:00 2001
From: Darafei Praliaskouski <komzpa@gmail.com>
Date: Sat, 11 May 2013 19:34:50 +0300
Subject: [PATCH] [geometry] add IsPointInsideTriangle implementation

---
 geometry/point2d.hpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/geometry/point2d.hpp b/geometry/point2d.hpp
index 5eac29a852..fe00af121f 100644
--- a/geometry/point2d.hpp
+++ b/geometry/point2d.hpp
@@ -199,6 +199,16 @@ namespace m2
     return res;
   }
 
+  template <typename T>
+  bool IsPointInsideTriangle(Point<T> const & p,
+                                     Point<T> const & a, Point<T> const & b, Point<T> const & c)
+  {
+    T const cpab = CrossProduct(b - a, p - a);
+    T const cpbc = CrossProduct(c - b, p - b);
+    T const cpca = CrossProduct(a - c, p - c);
+    return (cpab <= 0 && cpbc <= 0 && cpca <= 0) || (cpab >= 0 && cpbc >= 0 && cpca >= 0);
+  }
+
   template <typename T>
   bool IsPointStrictlyInsideTriangle(Point<T> const & p,
                                      Point<T> const & a, Point<T> const & b, Point<T> const & c)