added is_closed property

checks if the mesh is closed. if its closed, it adds faces from boundary vertices. if its open it does not add these faces to the mesh.

Author: nizartaha

src/compas/datastructures/mesh/slice.py

@@ -74,6 +74,10 @@ def is_line(self):
     @property
     def is_polygon(self):
         return len(self.intersections) >= 3
+    
+    @property
+    def is_closed(self):
+        return self.mesh.is_closed()
 
     @property
     def positive(self):
@@ -90,7 +94,8 @@ def positive(self):
         vdict = {key: self.mesh.vertex_coordinates(key) for key in vertices + self.intersections}
         fdict = [self.mesh.face_vertices(fkey) for fkey in faces]
         mesh = self.meshtype.from_vertices_and_faces(vdict, fdict)
-        mesh.add_face(mesh.vertices_on_boundary())
+        if self.is_closed:
+            mesh.add_face(mesh.vertices_on_boundary())
         return mesh
 
     def is_positive(self, key):
@@ -119,7 +124,8 @@ def negative(self):
         vdict = {key: self.mesh.vertex_coordinates(key) for key in vertices + self.intersections}
         fdict = [self.mesh.face_vertices(fkey) for fkey in faces]
         mesh = self.meshtype.from_vertices_and_faces(vdict, fdict)
-        mesh.add_face(mesh.vertices_on_boundary())
+        if self.is_closed:
+            mesh.add_face(mesh.vertices_on_boundary())
         return mesh
 
     def is_negative(self, key):