diff --git a/src/face_crawler.rs b/src/face_crawler.rs
index 63915bb..386a387 100644
--- a/src/face_crawler.rs
+++ b/src/face_crawler.rs
@@ -29,6 +29,8 @@ enum Transition<F,E,V>{
 				}
 				//test each edge collision time, ignoring roots with zero or conflicting derivative
 				for &edge_id in mesh.face_edges(face_id).iter(){
+					//this needs to be directed edge!
+					todo!();
 					let edge_n=mesh.edge_n(edge_id);
 					let n=n.cross(edge_n);
 					//picking a vert randomly is terrible