diff --git a/src/model_physics.rs b/src/model_physics.rs
index b045aae..72f10c8 100644
--- a/src/model_physics.rs
+++ b/src/model_physics.rs
@@ -597,6 +597,8 @@ enum EV{
 	Edge(MinkowskiEdge),
 }
 
+pub type GigaTime=Ratio<Fixed<4,128>,Fixed<4,128>>;
+
 impl MinkowskiMesh<'_>{
 	pub fn minkowski_sum<'a>(mesh0:TransformedMesh<'a>,mesh1:TransformedMesh<'a>)->MinkowskiMesh<'a>{
 		MinkowskiMesh{
@@ -709,7 +711,7 @@ impl MinkowskiMesh<'_>{
 			}
 		})
 	}
-	pub fn predict_collision_in(&self,relative_body:&crate::physics::Body,time_limit:integer::Time)->Option<(MinkowskiFace,integer::Time)>{
+	pub fn predict_collision_in(&self,relative_body:&crate::physics::Body,time_limit:integer::Time)->Option<(MinkowskiFace,GigaTime)>{
 		self.closest_fev_not_inside(relative_body.clone()).map_or(None,|fev|{
 			//continue forwards along the body parabola
 			match crate::face_crawler::crawl_fev(fev,self,relative_body,relative_body.time,time_limit){
@@ -718,7 +720,7 @@ impl MinkowskiMesh<'_>{
 			}
 		})
 	}
-	pub fn predict_collision_out(&self,relative_body:&crate::physics::Body,time_limit:integer::Time)->Option<(MinkowskiFace,integer::Time)>{
+	pub fn predict_collision_out(&self,relative_body:&crate::physics::Body,time_limit:integer::Time)->Option<(MinkowskiFace,GigaTime)>{
 		//create an extrapolated body at time_limit
 		let infinity_body=crate::physics::Body::new(
 			relative_body.extrapolated_position(time_limit),
@@ -734,10 +736,13 @@ impl MinkowskiMesh<'_>{
 			}
 		})
 	}
-	pub fn predict_collision_face_out(&self,relative_body:&crate::physics::Body,time_limit:integer::Time,contact_face_id:MinkowskiFace)->Option<(MinkowskiEdge,integer::Time)>{
+	pub fn predict_collision_face_out(&self,relative_body:&crate::physics::Body,time_limit:integer::Time,contact_face_id:MinkowskiFace)->Option<(MinkowskiEdge,GigaTime)>{
 		//no algorithm needed, there is only one state and two cases (Edge,None)
 		//determine when it passes an edge ("sliding off" case)
-		let mut best_time=time_limit;
+		let mut best_time={
+			let r=(time_limit-relative_body.time).to_ratio();
+			Ratio::new(r.num.fix_4(),r.den.fix_4())
+		};
 		let mut best_edge=None;
 		let face_n=self.face_nd(contact_face_id).0;
 		for &directed_edge_id in self.face_edges(contact_face_id).iter(){
@@ -747,10 +752,10 @@ impl MinkowskiMesh<'_>{
 			let verts=self.edge_verts(directed_edge_id.as_undirected());
 			let d=n.dot(self.vert(verts[0])+self.vert(verts[1]));
 			//WARNING! d outside of *2
-			for t in Fixed::<5,160>::zeroes2((n.dot(relative_body.position))*2-d,n.dot(relative_body.velocity)*2,n.dot(relative_body.acceleration)){
-				let t=relative_body.time.to_ratio().add_ratio(t);
-				if relative_body.time.to_ratio().lt_ratio(t)&&t.lt_ratio(best_time)&&n.dot(relative_body.extrapolated_velocity(t)).is_negative(){
-					best_time=t;
+			//WARNING: truncated precision
+			for dt in Fixed::<4,128>::zeroes2(((n.dot(relative_body.position))*2-d).fix_4(),n.dot(relative_body.velocity).fix_4()*2,n.dot(relative_body.acceleration).fix_4()){
+				if dt.num.is_positive()&&dt.lt_ratio(best_time)&&n.dot(relative_body.extrapolated_velocity_ratio_dt(dt)).is_negative(){
+					best_time=dt;
 					best_edge=Some(directed_edge_id);
 					break;
 				}
@@ -758,7 +763,7 @@ impl MinkowskiMesh<'_>{
 		}
 		best_edge.map(|e|(e.as_undirected(),best_time))
 	}
-	fn infinity_in(&self,infinity_body:crate::physics::Body)->Option<(MinkowskiFace,integer::Time)>{
+	fn infinity_in(&self,infinity_body:crate::physics::Body)->Option<(MinkowskiFace,GigaTime)>{
 		let infinity_fev=self.infinity_fev(-infinity_body.velocity,infinity_body.position);
 		match crate::face_crawler::crawl_fev(infinity_fev,self,&infinity_body,integer::Time::MIN,infinity_body.time){
 			crate::face_crawler::CrawlResult::Miss(_)=>None,