diff --git a/src/face_crawler.rs b/src/face_crawler.rs
index d6ad1a9..2e64cc2 100644
--- a/src/face_crawler.rs
+++ b/src/face_crawler.rs
@@ -34,7 +34,7 @@ impl<F:Copy,E:Copy,V:Copy> State<FEV<F,E,V>>{
 					}
 				}
 				//test each edge collision time, ignoring roots with zero or conflicting derivative
-				for &(edge_id,test_face_id) in mesh.face_edges(face_id){
+				for &(edge_id,test_face_id) in mesh.face_edges(face_id).iter(){
 					let (n,d)=mesh.face_nd(test_face_id);
 					for t in zeroes2((n.dot(body.position)-d)*2,n.dot(body.velocity)*2,n.dot(body.acceleration)){
 						let t=body.time+Time::from(t);
@@ -49,7 +49,7 @@ impl<F:Copy,E:Copy,V:Copy> State<FEV<F,E,V>>{
 			},
 			&FEV::<F,E,V>::Edge(edge_id)=>{
 				//test each face collision time, ignoring roots with zero or conflicting derivative
-				for &test_face_id in mesh.edge_side_faces(edge_id){
+				for &test_face_id in mesh.edge_side_faces(edge_id).iter(){
 					let (n,d)=mesh.face_nd(test_face_id);
 					for t in zeroes2((n.dot(body.position)-d)*2,n.dot(body.velocity)*2,n.dot(body.acceleration)){
 						let t=body.time+Time::from(t);
@@ -61,7 +61,7 @@ impl<F:Copy,E:Copy,V:Copy> State<FEV<F,E,V>>{
 					}
 				}
 				//test each vertex collision time, ignoring roots with zero or conflicting derivative
-				for &(vert_id,test_face_id) in mesh.edge_ends(edge_id){
+				for &(vert_id,test_face_id) in mesh.edge_ends(edge_id).iter(){
 					let (n,d)=mesh.face_nd(test_face_id);
 					for t in zeroes2((n.dot(body.position)-d)*2,n.dot(body.velocity)*2,n.dot(body.acceleration)){
 						let t=body.time+Time::from(t);
@@ -76,7 +76,7 @@ impl<F:Copy,E:Copy,V:Copy> State<FEV<F,E,V>>{
 			},
 			&FEV::<F,E,V>::Vert(vertex_id)=>{
 				//test each edge collision time, ignoring roots with zero or conflicting derivative
-				for &(edge_id,test_face_id) in mesh.vert_edges(vertex_id){
+				for &(edge_id,test_face_id) in mesh.vert_edges(vertex_id).iter(){
 					let (n,d)=mesh.face_nd(test_face_id);
 					for t in zeroes2((n.dot(body.position)-d)*2,n.dot(body.velocity)*2,n.dot(body.acceleration)){
 						let t=body.time+Time::from(t);
diff --git a/src/model_physics.rs b/src/model_physics.rs
index 5428015..47ef167 100644
--- a/src/model_physics.rs
+++ b/src/model_physics.rs
@@ -1,4 +1,5 @@
 use crate::integer::{Planar64,Planar64Vec3};
+use std::borrow::Cow;
 
 #[derive(Clone,Copy)]
 pub struct VertId(usize);
@@ -39,14 +40,14 @@ pub struct PhysicsMesh{
 	vert_topology:Vec<VertRefs>,
 }
 
-pub trait MeshQuery<FACE,EDGE,VERT>{
+pub trait MeshQuery<FACE:Clone,EDGE:Clone,VERT:Clone>{
 	fn closest_fev(&self,point:Planar64Vec3)->FEV<FACE,EDGE,VERT>;
 	fn face_nd(&self,face_id:FACE)->(Planar64Vec3,Planar64);
 	fn vert(&self,vert_id:VERT)->Planar64Vec3;
-	fn face_edges(&self,face_id:FACE)->&Vec<(EDGE,FACE)>;
-	fn edge_side_faces(&self,edge_id:EDGE)->&[FACE;2];
-	fn edge_ends(&self,edge_id:EDGE)->&[(VERT,FACE);2];
-	fn vert_edges(&self,vert_id:VERT)->&Vec<(EDGE,FACE)>;
+	fn face_edges(&self,face_id:FACE)->Cow<Vec<(EDGE,FACE)>>;
+	fn edge_side_faces(&self,edge_id:EDGE)->Cow<[FACE;2]>;
+	fn edge_ends(&self,edge_id:EDGE)->Cow<[(VERT,FACE);2]>;
+	fn vert_edges(&self,vert_id:VERT)->Cow<Vec<(EDGE,FACE)>>;
 }
 impl MeshQuery<FaceId,EdgeId,VertId> for PhysicsMesh{
 	fn closest_fev(&self,point:Planar64Vec3)->FEV<FaceId,EdgeId,VertId>{
@@ -60,17 +61,17 @@ impl MeshQuery<FaceId,EdgeId,VertId> for PhysicsMesh{
 	fn vert(&self,vert_id:VertId)->Planar64Vec3{
 		todo!()
 	}
-	fn face_edges(&self,face_id:FaceId)->&Vec<(EdgeId,FaceId)>{
-		&self.face_topology[face_id.0].edges
+	fn face_edges(&self,face_id:FaceId)->Cow<Vec<(EdgeId,FaceId)>>{
+		Cow::Borrowed(&self.face_topology[face_id.0].edges)
 	}
-	fn edge_side_faces(&self,edge_id:EdgeId)->&[FaceId;2]{
-		&self.edge_topology[edge_id.0].faces
+	fn edge_side_faces(&self,edge_id:EdgeId)->Cow<[FaceId;2]>{
+		Cow::Borrowed(&self.edge_topology[edge_id.0].faces)
 	}
-	fn edge_ends(&self,edge_id:EdgeId)->&[(VertId,FaceId);2]{
-		&self.edge_topology[edge_id.0].verts
+	fn edge_ends(&self,edge_id:EdgeId)->Cow<[(VertId,FaceId);2]>{
+		Cow::Borrowed(&self.edge_topology[edge_id.0].verts)
 	}
-	fn vert_edges(&self,vert_id:VertId)->&Vec<(EdgeId,FaceId)>{
-		&self.vert_topology[vert_id.0].edges
+	fn vert_edges(&self,vert_id:VertId)->Cow<Vec<(EdgeId,FaceId)>>{
+		Cow::Borrowed(&self.vert_topology[vert_id.0].edges)
 	}
 }
 
@@ -134,16 +135,16 @@ impl MeshQuery<MinkowskiFace,MinkowskiEdge,MinkowskiVert> for MinkowskiMesh<'_>{
 	fn vert(&self,vert_id:MinkowskiVert)->Planar64Vec3{
 		todo!()
 	}
-	fn face_edges(&self,face_id:MinkowskiFace)->&Vec<(MinkowskiEdge,MinkowskiFace)>{
+	fn face_edges(&self,face_id:MinkowskiFace)->Cow<Vec<(MinkowskiEdge,MinkowskiFace)>>{
 		todo!()
 	}
-	fn edge_side_faces(&self,edge_id:MinkowskiEdge)->&[MinkowskiFace;2]{
+	fn edge_side_faces(&self,edge_id:MinkowskiEdge)->Cow<[MinkowskiFace;2]>{
 		todo!()
 	}
-	fn edge_ends(&self,edge_id:MinkowskiEdge)->&[(MinkowskiVert,MinkowskiFace);2]{
+	fn edge_ends(&self,edge_id:MinkowskiEdge)->Cow<[(MinkowskiVert,MinkowskiFace);2]>{
 		todo!()
 	}
-	fn vert_edges(&self,vert_id:MinkowskiVert)->&Vec<(MinkowskiEdge,MinkowskiFace)>{
+	fn vert_edges(&self,vert_id:MinkowskiVert)->Cow<Vec<(MinkowskiEdge,MinkowskiFace)>>{
 		todo!()
 	}
 }