added NextCrease function to follows creases

vcg/simplex/face/pos.h

@@ -285,13 +285,41 @@ public:
         //assert(f->FFp(z)==f); // f is border along j
     }
 
+    /// Finds the next Crease half-edge border
+    /// TODO change crease flag with something more generic (per edge)
+    void NextCrease( )
+    {
+        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
+        assert(IsCrease()); // f is border along j
+        // Si deve cambiare faccia intorno allo stesso vertice v
+        //finche' non si trova una faccia di bordo.
+        do
+        {
+            FlipE();
+            if (!IsCrease()) FlipF();
+        }
+        while(!IsCrease());
+
+        // L'edge j e' di bordo e deve contenere v
+        assert(IsCrease() &&( f->V(z)==v || f->V(f->Next(z))==v ));
+
+        FlipV();
+        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
+    }
+
     /// Checks if the half-edge is of border
-    bool IsBorder()
+    bool IsBorder()const
     {
         return face::IsBorder(*f,z);
     }
 
-    bool IsFaux()
+    /// Checks if the half-edge is of crease
+    bool IsCrease() const
+    {
+        return f->IsCrease(z);
+    }
+
+    bool IsFaux() const
     {
         return (f->IsF(z));
     }