added boundary handling in pos

Former-commit-id: b57dcc5f6e4ca180d3eb6eca739bee0425922e94

include/igl/pos.h

@@ -5,6 +5,7 @@
 // This Source Code Form is subject to the terms of the Mozilla Public License 
 // v. 2.0. If a copy of the MPL was not distributed with this file, You can 
 // obtain one at http://mozilla.org/MPL/2.0/.
+
 #ifndef IGL_POS_H
 #define IGL_POS_H
 
@@ -29,30 +30,13 @@ template <typename S>
         )
     : F(F), FF(FF), FFi(FFi), fi(fi), ei(ei), reverse(reverse)
     {}
-
-//    // Init the pos by specifying Face,Vertex Index and Orientation
-//    Pos(Eigen::MatrixXi& F, 
-//        Eigen::MatrixXi& FF, 
-//        Eigen::MatrixXi& FFi, 
-//        int fi,
-//        int vi,
-//        bool reverse = false
-//        )
-//    : F(F), FF(FF), FFi(FFi), fi(fi), reverse(reverse)
-//    {
-//      ei = -1;
-//      for (int i=0;i<3;++i)
-//        if (F(fi,i) == vi)
-//          ei = i;
-//      assert(ei != -1);
-//      
-//      if (reverse)
-//        ei = (ei-1)%3;
-//    }
     
     // Change Face
     void flipF()
     {
+      if (isBorder())
+        return;
+      
       int fin = (*FF)(fi,ei);
       int ein = (*FFi)(fi,ei);
       int reversen = !reverse;
@@ -79,6 +63,42 @@ template <typename S>
       reverse = !reverse;
     }
     
+    bool isBorder()
+    {
+      return (*FF)(fi,ei) == -1;
+    }
+    
+    /*!
+     * Returns the next edge skipping the border
+     *      _________
+     *     /\ c | b /\
+     *    /  \  |  /  \
+     *   / d  \ | / a  \
+     *  /______\|/______\
+     *          v
+     * In this example, if a and d are of-border and the pos is iterating counterclockwise, this method iterate through the faces incident on vertex v,
+     * producing the sequence a, b, c, d, a, b, c, ...
+     */
+    bool NextFE()
+    {
+      if ( isBorder() ) // we are on a border
+      {
+        do
+        {
+					flipF();
+					flipE();
+        } while (!isBorder());
+        flipE();
+        return false;
+      }
+      else
+      {
+        flipF();
+        flipE();
+        return true;
+      }
+    }
+    
     // Get vertex index
     int Vi()
     {
@@ -98,6 +118,13 @@ template <typename S>
     {
       return fi;
     }
+
+    // Get edge index
+    int Ei()
+    {
+      return ei;
+    }
+
     
     bool operator==(Pos& p2)
     {
@@ -112,13 +139,14 @@ template <typename S>
        );
     }
     
+  private:
     int fi;
     int ei;
     bool reverse;
     
     const Eigen::Matrix<S, Eigen::Dynamic, Eigen::Dynamic>*     F;
-    Eigen::Matrix<S, Eigen::Dynamic, Eigen::Dynamic>*     FF;
-    Eigen::Matrix<S, Eigen::Dynamic, Eigen::Dynamic>*     FFi;
+    const Eigen::Matrix<S, Eigen::Dynamic, Eigen::Dynamic>*     FF;
+    const Eigen::Matrix<S, Eigen::Dynamic, Eigen::Dynamic>*     FFi;
   };
   
 }