Add comment on preconditions for Pobsopen.

diff --git a/lib/pathplan/vispath.h b/lib/pathplan/vispath.h
index 516e23dd7b99af453c23eb8459a861231c50b115..db9baefb8eb5427b7a42e8b1f0195eeeea6c5f47 100644 (file)
--- a/lib/pathplan/vispath.h
+++ b/lib/pathplan/vispath.h
@@ -26,7 +26,9 @@ extern "C" {
 #   define extern __EXPORT__
 #endif
 
-/* open a visibility graph */
+/* open a visibility graph 
+ * Points in polygonal obstacles must be in clockwise order.
+ */
     extern vconfig_t *Pobsopen(Ppoly_t ** obstacles, int n_obstacles);
 
 /* close a visibility graph, freeing its storage */