fix zoom

Former-commit-id: b0cb6afa46b77dfcc0cf91e3841294eef351fa14

tutorial/103_Events/main.cpp

@@ -15,11 +15,13 @@ bool key_down(igl::Viewer& viewer, unsigned char key, int modifier)
     // If a mesh is already displayed, draw_mesh returns an error if the given V and
     // F have size different than the current ones
     viewer.data.set_mesh(V1, F1);
+    viewer.core.align_camera_center(V1,F1);
   }
   else if (key == '2')
   {
     viewer.data.clear();
     viewer.data.set_mesh(V2, F2);
+    viewer.core.align_camera_center(V2,F2);
   }
 
   return false;