the bug

Cargo.lock

@@ -3904,6 +3904,7 @@ dependencies = [
  "arrayvec",
  "glam",
  "id",
+ "mlua",
  "strafesnet_common",
 ]
 

engine/physics/Cargo.toml

@@ -7,6 +7,7 @@ edition = "2024"
 arrayvec = "0.7.6"
 glam = "0.30.0"
 id = { version = "0.1.0", registry = "strafesnet" }
+mlua = { version = "0.11.5", features = ["luau"] }
 strafesnet_common = { path = "../../lib/common", registry = "strafesnet" }
 
 [lints]

engine/physics/src/lib.rs

@@ -3,6 +3,7 @@ mod face_crawler;
 mod model;
 mod push_solve;
 mod minimum_difference;
+mod minimum_difference_lua;
 
 pub mod physics;
 

engine/physics/src/minimum_difference.rs

@@ -10,7 +10,7 @@ use crate::model::{MinkowskiMesh,MinkowskiVert};
 // written by Trey Reynolds in 2021
 
 type Simplex<const N:usize,Vert>=[Vert;N];
-#[derive(Clone,Copy)]
+#[derive(Clone,Copy,Debug)]
 enum Simplex1_3<Vert>{
 	Simplex1(Simplex<1,Vert>),
 	Simplex2(Simplex<2,Vert>),
@@ -136,12 +136,15 @@ fn reduce1<M:MeshQuery>(
 	mesh:&M,
 	point:Planar64Vec3,
 )->Reduced<M::Vert>{
+	println!("reduce1");
 	// --debug.profilebegin("reduceSimplex0")
 	// local a = a1 - a0
 	let p0=mesh.vert(v0);
 
+	println!("p0={p0}");
 	// local p = -a
 	let p=-(p0+point);
+	println!("p={p}");
 
 	// local direction = p
 	let mut dir=p;
@@ -165,6 +168,7 @@ fn reduce2<M:MeshQuery>(
 	mesh:&M,
 	point:Planar64Vec3,
 )->Reduced<M::Vert>{
+	println!("reduce2");
 	// --debug.profilebegin("reduceSimplex1")
 	// local a = a1 - a0
 	// local b = b1 - b0
@@ -222,6 +226,7 @@ fn reduce3<M:MeshQuery>(
 	mesh:&M,
 	point:Planar64Vec3,
 )->Reduced<M::Vert>{
+	println!("reduce3");
 	// --debug.profilebegin("reduceSimplex2")
 	// local a = a1 - a0
 	// local b = b1 - b0
@@ -331,6 +336,7 @@ fn reduce4<M:MeshQuery>(
 	mesh:&M,
 	point:Planar64Vec3,
 )->Reduce<M::Vert>{
+	println!("reduce4");
 	// --debug.profilebegin("reduceSimplex3")
 	// local a = a1 - a0
 	// local b = b1 - b0
@@ -349,6 +355,10 @@ fn reduce4<M:MeshQuery>(
 	let mut u=p1-p0;
 	let mut v=p2-p0;
 	let w=p3-p0;
+	println!("p={p}");
+	println!("u={u}");
+	println!("v={v}");
+	println!("w={w}");
 
 	// local uv = u:Cross(v)
 	// local vw = v:Cross(w)
@@ -367,8 +377,8 @@ fn reduce4<M:MeshQuery>(
 
 	// if pvw/uvw >= 0 and upw/uvw >= 0 and uvp/uvw >= 0 then
 	if !pv_w.div_sign(uv_w).is_negative()
-	 ||!up_w.div_sign(uv_w).is_negative()
-	 ||!uv_p.div_sign(uv_w).is_negative(){
+	 &&!up_w.div_sign(uv_w).is_negative()
+	 &&!uv_p.div_sign(uv_w).is_negative(){
 		// origin is contained, this is a positive detection
 		// local direction = Vector3.new(0, 0, 0)
 		// return direction, a0, a1, b0, b1, c0, c1, d0, d1
@@ -396,8 +406,6 @@ fn reduce4<M:MeshQuery>(
 			// b0, c0 = c0, d0
 			// b1, c1 = c1, d1
 			(v1,v2)=(v2,v3);
-		}else{
-			v2=v3;
 		}
 	}else{
 		// elseif wuDist == minDist3 then
@@ -410,8 +418,6 @@ fn reduce4<M:MeshQuery>(
 			// before [a,b,c,d]
 			(v1,v2)=(v3,v1);
 			// after [a,d,b]
-		}else{
-			v2=v3;
 		}
 	}
 
@@ -423,17 +429,23 @@ fn reduce4<M:MeshQuery>(
 	let pv=p.cross(v);
 	let uv_up=uv.dot(up);
 	let uv_pv=uv.dot(pv);
+	println!("up={up}");
+	println!("pv={pv}");
+	println!("uv_up={uv_up}");
+	println!("uv_pv={uv_pv}");
 
 	// if uv_up >= 0 and uv_pv >= 0 then
 	if !uv_up.is_negative()&&!uv_pv.is_negative(){
 		// local direction = uvw < 0 and uv or -uv
 		// return direction, a0, a1, b0, b1, c0, c1
 		if uv_w.is_negative(){
+			println!("a");
 			return Reduce::Reduced(Reduced{
 				dir:narrow_dir2(uv),
 				simplex:Simplex1_3::Simplex3([v0,v1,v2]),
 			});
 		}else{
+			println!("b");
 			return Reduce::Reduced(Reduced{
 				dir:narrow_dir2(-uv),
 				simplex:Simplex1_3::Simplex3([v0,v1,v2]),
@@ -471,11 +483,13 @@ fn reduce4<M:MeshQuery>(
 			// direction = uvw < 0 and uv or -uv
 			// return direction, a0, a1, b0, b1
 			if uv_w.is_negative(){
+				println!("c");
 				return Reduce::Reduced(Reduced{
 					dir:narrow_dir2(uv),
 					simplex:Simplex1_3::Simplex2([v0,v1]),
 				});
 			}else{
+				println!("d");
 				return Reduce::Reduced(Reduced{
 					dir:narrow_dir2(-uv),
 					simplex:Simplex1_3::Simplex2([v0,v1]),
@@ -483,6 +497,7 @@ fn reduce4<M:MeshQuery>(
 			}
 		}
 
+		println!("e");
 		// return direction, a0, a1, b0, b1
 		return Reduce::Reduced(Reduced{
 			dir:narrow_dir3(direction),
@@ -496,11 +511,13 @@ fn reduce4<M:MeshQuery>(
 	if dir==vec3::zero(){
 		// direction = uvw < 0 and uv or -uv
 		if uv_w.is_negative(){
+			println!("f");
 			return Reduce::Reduced(Reduced{
 				dir:narrow_dir2(uv),
 				simplex:Simplex1_3::Simplex1([v0]),
 			});
 		}else{
+			println!("g");
 			return Reduce::Reduced(Reduced{
 				dir:narrow_dir2(-uv),
 				simplex:Simplex1_3::Simplex1([v0]),
@@ -508,6 +525,7 @@ fn reduce4<M:MeshQuery>(
 		}
 	}
 
+	println!("h");
 	// return direction, a0, a1
 	Reduce::Reduced(Reduced{
 		dir,
@@ -535,24 +553,6 @@ impl<Vert> Simplex2_4<Vert>{
 	}
 }
 
-pub fn contains_point(mesh:&MinkowskiMesh<'_>,point:Planar64Vec3)->bool{
-	const ENABLE_FAST_FAIL:bool=true;
-	// TODO: remove mesh negation
-	minimum_difference::<ENABLE_FAST_FAIL,_,_>(&-mesh,point,
-		// on_exact
-		|is_intersecting,_simplex|{
-			is_intersecting
-		},
-		// on_escape
-		|_simplex|{
-			// intersection is guaranteed at this point
-			true
-		},
-		// fast_fail value
-		||false
-	)
-}
-
 //infinity fev algorithm state transition
 #[derive(Debug)]
 enum Transition<Vert>{
@@ -752,27 +752,35 @@ fn crawl_to_closest_fev<'a>(mesh:&MinkowskiMesh<'a>,simplex:Simplex<3,MinkowskiV
 	}
 }
 
-pub fn closest_fev_not_inside<'a>(mesh:&MinkowskiMesh<'a>,point:Planar64Vec3)->Option<FEV<MinkowskiMesh<'a>>>{
+#[derive(Debug)]
+pub struct InfiniteLoop;
+pub fn closest_fev_not_inside<'a>(mesh:&MinkowskiMesh<'a>,point:Planar64Vec3)->Result<Option<FEV<MinkowskiMesh<'a>>>,InfiniteLoop>{
+	println!("=== LUA ===");
+	let (hits,_details)=crate::minimum_difference_lua::minimum_difference_details(mesh,point).unwrap();
+	println!("=== RUST ===");
+	let closest_fev_not_inside=closest_fev_not_inside_inner(mesh,point).unwrap();
+	assert_eq!(hits,closest_fev_not_inside.is_none(),"algorithms disagree");
+	Ok(closest_fev_not_inside)
+}
+
+pub fn closest_fev_not_inside_inner<'a>(mesh:&MinkowskiMesh<'a>,point:Planar64Vec3)->Result<Option<FEV<MinkowskiMesh<'a>>>,InfiniteLoop>{
 	const ENABLE_FAST_FAIL:bool=false;
 	// TODO: remove mesh negation
 	minimum_difference::<ENABLE_FAST_FAIL,_,_>(&-mesh,point,
 		// on_exact
 		|is_intersecting,simplex|{
+			println!("on_exact simplex={simplex:?}");
 			if is_intersecting{
-				return None;
+				return Ok(None);
 			}
 			// Convert simplex to FEV
 			// Vertices must be inverted since the mesh is inverted
-			Some(match simplex{
+			Ok(Some(match simplex{
 				Simplex1_3::Simplex1([v0])=>FEV::Vert(-v0),
 				Simplex1_3::Simplex2([v0,v1])=>{
 					// invert
 					let (v0,v1)=(-v0,-v1);
-					let ev=crawl_to_closest_ev(mesh,[v0,v1],point);
-					if !matches!(ev,EV::Edge(_)){
-						println!("I can't believe it's not an edge!");
-					}
-					ev.into()
+					crawl_to_closest_ev(mesh,[v0,v1],point).into()
 				},
 				Simplex1_3::Simplex3([v0,v1,v2])=>{
 					// invert
@@ -780,23 +788,40 @@ pub fn closest_fev_not_inside<'a>(mesh:&MinkowskiMesh<'a>,point:Planar64Vec3)->O
 					// Shimmy to the side until you find a face that contains the closest point
 					// it's ALWAYS representable as a face, but this algorithm may
 					// return E or V in edge cases but I don't think that will break the face crawler
-					let fev=crawl_to_closest_fev(mesh,[v0,v1,v2],point);
-					if !matches!(fev,FEV::Face(_)){
-						println!("I can't believe it's not a face!");
-					}
-					fev
+					crawl_to_closest_fev(mesh,[v0,v1,v2],point)
 				},
-			})
+			}))
 		},
 		// on_escape
 		|_simplex|{
 			// intersection is guaranteed at this point
 			// local norm, dist, u0, u1, v0, v1, w0, w1 = expand(queryP, queryQ, a0, a1, b0, b1, c0, c1, d0, d1, 1e-5)
 			// let simplex=refine_to_exact(mesh,simplex);
-			None
+			Ok(None)
 		},
 		// fast_fail value is irrelevant and will never be returned!
-		||unreachable!()
+		||unreachable!(),
+		||Err(InfiniteLoop),
+	)
+}
+
+pub fn contains_point(mesh:&MinkowskiMesh<'_>,point:Planar64Vec3)->bool{
+	const ENABLE_FAST_FAIL:bool=true;
+	// TODO: remove mesh negation
+	minimum_difference::<ENABLE_FAST_FAIL,_,_>(&-mesh,point,
+		// on_exact
+		|is_intersecting,_simplex|{
+			is_intersecting
+		},
+		// on_escape
+		|_simplex|{
+			// intersection is guaranteed at this point
+			true
+		},
+		// fast_fail value
+		||false,
+		// infinite loop
+		||false,
 	)
 }
 
@@ -811,6 +836,7 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T,M:MeshQuery>(
 	on_exact:impl FnOnce(bool,Simplex1_3<M::Vert>)->T,
 	on_escape:impl FnOnce(Simplex<4,M::Vert>)->T,
 	on_fast_fail:impl FnOnce()->T,
+	on_infinite_loop:impl FnOnce()->T,
 )->T{
 	// local initialAxis = queryQ() - queryP()
 	// local new_point_p = queryP(initialAxis)
@@ -821,6 +847,7 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T,M:MeshQuery>(
 	if initial_axis==vec3::zero(){
 		initial_axis=choose_any_direction();
 	}
+	println!("initial_axis={initial_axis}");
 	let last_point=mesh.farthest_vert(-initial_axis);
 	// this represents the 'a' value in the commented code
 	let mut last_pos=mesh.vert(last_point);
@@ -828,7 +855,9 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T,M:MeshQuery>(
 
 	// exitRadius = testIntersection and 0 or exitRadius or 1/0
 	// for _ = 1, 100 do
-	loop{
+	for _ in 0..100{
+		println!("direction={direction}");
+
 		// new_point_p = queryP(-direction)
 		// new_point_q = queryQ(direction)
 		// local next_point = new_point_q - new_point_p
@@ -836,7 +865,11 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T,M:MeshQuery>(
 		let next_pos=mesh.vert(next_point);
 
 		// if -direction:Dot(next_point) > (exitRadius + radiusP + radiusQ)*direction.magnitude then
-		if ENABLE_FAST_FAIL&&direction.dot(next_pos+point).is_negative(){
+		let d=direction.dot(next_pos+point);
+		let fast_fail=d.is_negative();
+		println!("ENABLE_FAST_FAIL={ENABLE_FAST_FAIL} fast_fail={fast_fail} next_point={} dot={d}",next_pos+point);
+		if ENABLE_FAST_FAIL&&fast_fail{
+			println!("on_fast_fail");
 			return on_fast_fail();
 		}
 
@@ -845,8 +878,11 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T,M:MeshQuery>(
 		// if
 		// 	direction:Dot(next_point - a) <= 0 or
 		// 	absDet(next_point, a, b, c) < 1e-6
-		if !direction.dot(next_pos-last_pos).is_positive()
-		||simplex_big.det_is_zero(mesh){
+		let cond1=!direction.dot(next_pos-last_pos).is_positive();
+		let cond2=simplex_big.det_is_zero(mesh);
+		println!("cond1={cond1} cond2={cond2}");
+		if cond1||cond2{
+			println!("on_exact");
 			// Found enough information to compute the exact closest point.
 			// local norm = direction.unit
 			// local dist = a:Dot(norm)
@@ -859,6 +895,7 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T,M:MeshQuery>(
 		match simplex_big.reduce(mesh,point){
 			// if a and b and c and d then
 			Reduce::Escape(simplex)=>{
+				println!("on_escape");
 				// Enough information to conclude that the meshes are intersecting.
 				// Topology information is computed if needed.
 				return on_escape(simplex);
@@ -872,6 +909,7 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T,M:MeshQuery>(
 		// next loop this will be a
 		last_pos=next_pos;
 	}
+	on_infinite_loop()
 }
 
 #[cfg(test)]
@@ -893,7 +931,8 @@ mod test{
 				true
 			},
 			// fast_fail value
-			||false
+			||false,
+			||false,
 		)
 	}
 

engine/physics/src/minimum_difference_lua.rs

@@ -0,0 +1,173 @@
+use mlua::{Lua,FromLuaMulti,IntoLuaMulti,Function,Result as LuaResult,Vector};
+use strafesnet_common::integer::{Planar64,Planar64Vec3,FixedFromFloatError};
+
+use crate::model::{MeshQuery,MinkowskiMesh};
+
+pub fn contains_point(
+	mesh:&MinkowskiMesh,
+	point:Planar64Vec3,
+)->LuaResult<bool>{
+	Ok(minimum_difference(mesh,point,true)?.hits)
+}
+pub fn minimum_difference_details(
+	mesh:&MinkowskiMesh,
+	point:Planar64Vec3,
+)->LuaResult<(bool,Option<Details>)>{
+	let md=minimum_difference(mesh,point,false)?;
+	Ok((md.hits,md.details))
+}
+fn p64v3(v:Vector)->Result<Planar64Vec3,FixedFromFloatError>{
+	Ok(Planar64Vec3::new([
+		v.x().try_into()?,
+		v.y().try_into()?,
+		v.z().try_into()?,
+	]))
+}
+fn vec(v:Planar64Vec3)->Vector{
+	Vector::new(v.x.into(),v.y.into(),v.z.into())
+}
+struct MinimumDifference{
+	hits:bool,
+	details:Option<Details>
+}
+pub struct Details{
+	pub distance:Planar64,
+	pub p_pos:Planar64Vec3,
+	pub p_norm:Planar64Vec3,
+	pub q_pos:Planar64Vec3,
+	pub q_norm:Planar64Vec3,
+}
+impl FromLuaMulti for MinimumDifference{
+	fn from_lua_multi(mut values:mlua::MultiValue,_lua:&Lua)->LuaResult<Self>{
+		match values.make_contiguous(){
+			&mut [
+				mlua::Value::Boolean(hits),
+				mlua::Value::Nil,
+				mlua::Value::Nil,
+				mlua::Value::Nil,
+				mlua::Value::Nil,
+				mlua::Value::Nil,
+			]=>Ok(Self{hits,details:None}),
+			&mut [
+				mlua::Value::Boolean(hits),
+				mlua::Value::Number(distance),
+				mlua::Value::Vector(p_pos),
+				mlua::Value::Vector(p_norm),
+				mlua::Value::Vector(q_pos),
+				mlua::Value::Vector(q_norm),
+			]=>Ok(Self{
+				hits,
+				details:Some(Details{
+					distance:distance.try_into().unwrap(),
+					p_pos:p64v3(p_pos).unwrap(),
+					p_norm:p64v3(p_norm).unwrap(),
+					q_pos:p64v3(q_pos).unwrap(),
+					q_norm:p64v3(q_norm).unwrap(),
+				}),
+			}),
+			&mut [
+				mlua::Value::Boolean(hits),
+				mlua::Value::Integer(distance),
+				mlua::Value::Vector(p_pos),
+				mlua::Value::Vector(p_norm),
+				mlua::Value::Vector(q_pos),
+				mlua::Value::Vector(q_norm),
+			]=>Ok(Self{
+				hits,
+				details:Some(Details{
+					distance:distance.into(),
+					p_pos:p64v3(p_pos).unwrap(),
+					p_norm:p64v3(p_norm).unwrap(),
+					q_pos:p64v3(q_pos).unwrap(),
+					q_norm:p64v3(q_norm).unwrap(),
+				}),
+			}),
+			values=>Err(mlua::Error::runtime(format!("Invalid return values: {values:?}"))),
+		}
+	}
+}
+
+struct Args{
+	query_p:Function,
+	radius_p:f64,
+	query_q:Function,
+	radius_q:f64,
+	test_intersection:bool,
+}
+impl Args{
+	fn new(
+		lua:&Lua,
+		mesh:&'static MinkowskiMesh<'static>,
+		point:Planar64Vec3,
+		test_intersection:bool,
+	)->LuaResult<Self>{
+		let radius_p=0.0;
+		let radius_q=0.0;
+		// Query the farthest point on the mesh in the given direction.
+		let query_p=lua.create_function(move|_,dir:Option<Vector>|{
+			let Some(dir)=dir else{
+				return Ok(vec(mesh.mesh0.hint_point()));
+			};
+			let dir=p64v3(dir).unwrap();
+			let vert_id=mesh.mesh0.farthest_vert(dir);
+			let dir=mesh.mesh0.vert(vert_id);
+			Ok(vec(dir))
+		})?;
+		// query_q is different since it includes the test point offset.
+		let query_q=lua.create_function(move|_,dir:Option<Vector>|{
+			let Some(dir)=dir else{
+				return Ok(vec(mesh.mesh1.hint_point()+point));
+			};
+			let dir=p64v3(dir).unwrap();
+			let vert_id=mesh.mesh1.farthest_vert(dir);
+			let dir=mesh.mesh1.vert(vert_id)+point;
+			Ok(vec(dir))
+		})?;
+		Ok(Args{
+			query_p,
+			radius_p,
+			query_q,
+			radius_q,
+			test_intersection,
+		})
+	}
+}
+impl IntoLuaMulti for Args{
+	fn into_lua_multi(self,lua:&Lua)->LuaResult<mlua::MultiValue>{
+		use mlua::IntoLua;
+		Ok(mlua::MultiValue::from_vec(vec![
+			self.query_p.into_lua(lua)?,
+			self.radius_p.into_lua(lua)?,
+			self.query_q.into_lua(lua)?,
+			self.radius_q.into_lua(lua)?,
+			mlua::Value::Nil,
+			self.test_intersection.into_lua(lua)?,
+		]))
+	}
+}
+
+fn minimum_difference(
+	mesh:&MinkowskiMesh,
+	point:Planar64Vec3,
+	test_intersection:bool,
+)->LuaResult<MinimumDifference>{
+	let ctx=init_lua()?;
+	// SAFETY: mesh lifetime must outlive args usages
+	let mesh=unsafe{core::mem::transmute(mesh)};
+	let args=Args::new(&ctx.lua,mesh,point,test_intersection)?;
+	ctx.f.call(args)
+}
+
+struct Ctx{
+	lua:Lua,
+	f:Function,
+}
+fn init_lua()->LuaResult<Ctx>{
+	static SOURCE:std::sync::LazyLock<String>=std::sync::LazyLock::new(||std::fs::read_to_string("Trey-MinimumDifference.lua").unwrap());
+	let lua=Lua::new();
+	lua.sandbox(true)?;
+	let lib_f=lua.load(SOURCE.as_str()).set_name("Trey-MinimumDifference").into_function()?;
+	let lib:mlua::Table=lib_f.call(())?;
+	let f=lib.raw_get("difference")?;
+	Ok(Ctx{lua,f})
+}

engine/physics/src/model.rs

@@ -91,7 +91,6 @@ pub trait MeshQuery{
 		(self.vert(v1)-self.vert(v0))*((directed_edge_id.parity() as i64)*2-1)
 	}
 	/// This must return a point inside the mesh.
-	#[expect(dead_code)]
 	fn hint_point(&self)->Planar64Vec3;
 	fn farthest_vert(&self,dir:Planar64Vec3)->Self::Vert;
 	fn vert(&self,vert_id:Self::Vert)->Planar64Vec3;
@@ -646,8 +645,8 @@ pub enum MinkowskiFace{
 
 #[derive(Debug)]
 pub struct MinkowskiMesh<'a>{
-	mesh0:TransformedMesh<'a>,
-	mesh1:TransformedMesh<'a>,
+	pub mesh0:TransformedMesh<'a>,
+	pub mesh1:TransformedMesh<'a>,
 }
 
 pub type GigaTime=Ratio<Fixed<4,128>,Fixed<4,128>>;
@@ -671,12 +670,14 @@ impl MinkowskiMesh<'_>{
 			mesh1,
 		}
 	}
-	pub fn predict_collision_in(&self,relative_body:&Body,range:impl RangeBounds<Time>)->Option<(MinkowskiFace,GigaTime)>{
-		let fev=crate::minimum_difference::closest_fev_not_inside(self,relative_body.position)?;
+	pub fn predict_collision_in(&self,relative_body:&Body,range:impl RangeBounds<Time>)->Result<Option<(MinkowskiFace,GigaTime)>,crate::minimum_difference::InfiniteLoop>{
+		let Some(fev)=crate::minimum_difference::closest_fev_not_inside(self,relative_body.position)?else{
+			return Ok(None);
+		};
 		//continue forwards along the body parabola
-		fev.crawl(self,relative_body,range.start_bound(),range.end_bound()).hit()
+		Ok(fev.crawl(self,relative_body,range.start_bound(),range.end_bound()).hit())
 	}
-	pub fn predict_collision_out(&self,relative_body:&Body,range:impl RangeBounds<Time>)->Option<(MinkowskiFace,GigaTime)>{
+	pub fn predict_collision_out(&self,relative_body:&Body,range:impl RangeBounds<Time>)->Result<Option<(MinkowskiFace,GigaTime)>,crate::minimum_difference::InfiniteLoop>{
 		let (lower_bound,upper_bound)=(range.start_bound(),range.end_bound());
 		// TODO: handle unbounded collision using infinity fev
 		let time=match upper_bound{
@@ -684,14 +685,16 @@ impl MinkowskiMesh<'_>{
 			Bound::Excluded(&time)=>time,
 			Bound::Unbounded=>unimplemented!("unbounded collision out"),
 		};
-		let fev=crate::minimum_difference::closest_fev_not_inside(self,relative_body.extrapolated_position(time))?;
+		let Some(fev)=crate::minimum_difference::closest_fev_not_inside(self,relative_body.extrapolated_position(time))?else{
+			return Ok(None);
+		};
 		// swap and negate bounds to do a time inversion
 		let (lower_bound,upper_bound)=(upper_bound.map(|&t|-t),lower_bound.map(|&t|-t));
 		let infinity_body=-relative_body;
 		//continue backwards along the body parabola
-		fev.crawl(self,&infinity_body,lower_bound.as_ref(),upper_bound.as_ref()).hit()
+		Ok(fev.crawl(self,&infinity_body,lower_bound.as_ref(),upper_bound.as_ref()).hit()
 			//no need to test -time<time_limit because of the first step
-			.map(|(face,time)|(face,-time))
+			.map(|(face,time)|(face,-time)))
 	}
 	pub fn predict_collision_face_out(&self,relative_body:&Body,range:impl RangeBounds<Time>,contact_face_id:MinkowskiFace)->Option<(MinkowskiDirectedEdge,GigaTime)>{
 		// TODO: make better

engine/physics/src/physics.rs

@@ -828,7 +828,7 @@ impl TouchingState{
 		}).collect();
 		crate::push_solve::push_solve(&contacts,acceleration)
 	}
-	fn predict_collision_end(&self,collector:&mut instruction::InstructionCollector<InternalInstruction,Time>,models:&PhysicsModels,hitbox_mesh:&HitboxMesh,body:&Body,start_time:Time){
+	fn predict_collision_end(&self,collector:&mut instruction::InstructionCollector<InternalInstruction,Time>,models:&PhysicsModels,hitbox_mesh:&HitboxMesh,body:&Body,start_time:Time)->Result<(),crate::minimum_difference::InfiniteLoop>{
 		// let relative_body=body.relative_to(&Body::ZERO);
 		let relative_body=body;
 		for (convex_mesh_id,face_id) in &self.contacts{
@@ -849,7 +849,7 @@ impl TouchingState{
 			//detect model collision in reverse
 			let model_mesh=models.intersect_mesh(convex_mesh_id);
 			let minkowski=model_physics::MinkowskiMesh::minkowski_sum(model_mesh,hitbox_mesh.transformed_mesh());
-			collector.collect(minkowski.predict_collision_out(&relative_body,start_time..collector.time()).map(|(_face,time)|{
+			collector.collect(minkowski.predict_collision_out(&relative_body,start_time..collector.time())?.map(|(_face,time)|{
 				TimedInstruction{
 					time:relative_body.time+time.into(),
 					instruction:InternalInstruction::CollisionEnd(
@@ -859,6 +859,7 @@ impl TouchingState{
 				}
 			}));
 		}
+		Ok(())
 	}
 }
 
@@ -1199,7 +1200,7 @@ impl<'a> PhysicsContext<'a>{
 		collector.collect(state.next_move_instruction());
 
 		//check for collision ends
-		state.touching.predict_collision_end(&mut collector,&data.models,&data.hitbox_mesh,&state.body,state.time);
+		state.touching.predict_collision_end(&mut collector,&data.models,&data.hitbox_mesh,&state.body,state.time).unwrap();
 		//check for collision starts
 		let mut aabb=aabb::Aabb::default();
 		state.body.grow_aabb(&mut aabb,state.time,collector.time());
@@ -1214,17 +1215,17 @@ impl<'a> PhysicsContext<'a>{
 			//no checks are needed because of the time limits.
 			let model_mesh=data.models.mesh(*convex_mesh_id);
 			let minkowski=model_physics::MinkowskiMesh::minkowski_sum(model_mesh,data.hitbox_mesh.transformed_mesh());
-			collector.collect(minkowski.predict_collision_in(relative_body,state.time..collector.time())
-				.map(|(face,dt)|
-					TimedInstruction{
-						time:relative_body.time+dt.into(),
-						instruction:InternalInstruction::CollisionStart(
-							Collision::new(*convex_mesh_id,face),
-							dt
-						)
-					}
+			let Ok(collision)=minkowski.predict_collision_in(relative_body,state.time..collector.time())else{
+				println!("Infinite loop! body={relative_body}");
+				return;
+			};
+			collector.collect(collision.map(|(face,dt)|TimedInstruction{
+				time:relative_body.time+dt.into(),
+				instruction:InternalInstruction::CollisionStart(
+					Collision::new(*convex_mesh_id,face),
+					dt
 				)
-			);
+			}));
 		});
 		collector.take()
 	}
@@ -1972,7 +1973,7 @@ mod test{
 		let hitbox_mesh=h1.transformed_mesh();
 		let platform_mesh=h0.transformed_mesh();
 		let minkowski=model_physics::MinkowskiMesh::minkowski_sum(platform_mesh,hitbox_mesh);
-		let collision=minkowski.predict_collision_in(&relative_body,Time::ZERO..Time::from_secs(10));
+		let collision=minkowski.predict_collision_in(&relative_body,Time::ZERO..Time::from_secs(10)).unwrap();
 		assert_eq!(collision.map(|tup|relative_body.time+tup.1.into()),expected_collision_time,"Incorrect time of collision");
 	}
 	fn test_collision_rotated(relative_body:Body,expected_collision_time:Option<Time>){
@@ -1990,7 +1991,7 @@ mod test{
 		let hitbox_mesh=h1.transformed_mesh();
 		let platform_mesh=h0.transformed_mesh();
 		let minkowski=model_physics::MinkowskiMesh::minkowski_sum(platform_mesh,hitbox_mesh);
-		let collision=minkowski.predict_collision_in(&relative_body,Time::ZERO..Time::from_secs(10));
+		let collision=minkowski.predict_collision_in(&relative_body,Time::ZERO..Time::from_secs(10)).unwrap();
 		assert_eq!(collision.map(|tup|relative_body.time+tup.1.into()),expected_collision_time,"Incorrect time of collision");
 	}
 	fn test_collision(relative_body:Body,expected_collision_time:Option<Time>){

integration-testing/src/test_scenes.rs

@@ -115,3 +115,40 @@ fn bug_3(){
 	assert_eq!(body.acceleration,vec3::int(0,0,0));
 	assert_eq!(body.time,Time::from_secs(2));
 }
+
+fn test_scene_cylinder()->PhysicsData{
+	let mut builder=TestSceneBuilder::new();
+	let cube_face_description=CubeFaceDescription::new(Default::default(),RenderConfigId::new(0));
+	let mesh=builder.push_mesh(strafesnet_rbx_loader::primitives::unit_cylinder(cube_face_description));
+	// place one 5x5x5 cylinder.
+	builder.push_mesh_instance(mesh,Planar64Affine3::new(
+		mat3::from_diagonal(vec3::int(5,5,5)>>1),
+		vec3::int(0,-5,0)
+	));
+	builder.build()
+}
+
+#[test]
+fn test_minimum_difference(){
+	let physics_data=test_scene_cylinder();
+	let body=strafesnet_physics::physics::Body::new(
+		vec3::int(4,1,4)>>1,
+		vec3::int(-1,-1,-2),
+		vec3::int(0,-100,0),
+		Time::ZERO,
+	);
+	let mut physics=PhysicsState::new_with_body(body);
+	physics.style_mut().gravity=vec3::zero();
+	let mut phys_iter=PhysicsContext::iter_internal(&mut physics,&physics_data,Time::from_secs(3))
+		.filter(|ins|!matches!(ins.instruction,InternalInstruction::StrafeTick));
+	// touch side of part at 0,0,0
+	assert_eq!(phys_iter.next().unwrap().time,Time::from_secs(1));
+	// touch top of part at 5,-5,0
+	assert_eq!(phys_iter.next().unwrap().time,Time::from_secs(2));
+	assert!(phys_iter.next().is_none());
+	let body=physics.body();
+	assert_eq!(body.position,vec3::int(5+2,0,0)>>1);
+	assert_eq!(body.velocity,vec3::int(0,0,0));
+	assert_eq!(body.acceleration,vec3::int(0,0,0));
+	assert_eq!(body.time,Time::from_secs(2));
+}

integration-testing/src/tests.rs

@@ -74,3 +74,39 @@ fn physics_bug_3()->Result<(),ReplayError>{
 
 	Ok(())
 }
+
+// Infinite loop! body=p(-1796.657, 677.618, 36.959) v(3.158, -53.650, -34.435) a(-0.000, -71.276, -45.248) t(288s+440000000ns)
+// Infinite loop! body=p(-2382.440, 160.150, -379.151) v(53.632, 35.779, 44.904) a(0.000, -100.000, 0.000) t(306s+675758543ns)
+// Infinite loop! body=p(-1798.724, 731.459, 68.784) v(-17.389, 0.000, -78.087) a(0.000, 0.000, 0.000) t(284s+006980061ns)
+// Infinite loop! body=p(-1796.657, 677.618, 36.959) v(3.158, -53.650, -34.435) a(-0.000, -71.276, -45.248) t(288s+440000000ns)
+// Infinite loop! body=p(-1797.504, 738.529, 74.864) v(-3.653, 0.000, -79.917) a(0.000, 0.000, 0.000) t(282s+709871336ns)
+// Infinite loop! body=p(-1797.569, 735.449, 71.859) v(23.726, -76.309, -3.747) a(0.000, 0.000, 0.000) t(283s+325193187ns)
+
+#[test]
+fn physics_md_infinite_loop()->Result<(),ReplayError>{
+	println!("loading map file..");
+	let data=read_entire_file("../tools/bhop_maps/5692113331.snfm")?;
+	let map=strafesnet_snf::read_map(data)?.into_complete_map()?;
+
+	// create recording
+	println!("generating models..");
+	let physics_data=PhysicsData::new(&map);
+	println!("simulating...");
+
+	//teleport to bug
+	use strafesnet_common::integer::{vec3,Time};
+	let body=strafesnet_physics::physics::Body::new(
+		vec3::try_from_f32_array([-1796.657, 677.618, 36.959]).unwrap(),
+		vec3::try_from_f32_array([3.158, -53.650, -34.435]).unwrap(),
+		vec3::int(0,-100,0),
+		Time::ZERO,
+	);
+	let mut physics=PhysicsState::new_with_body(body);
+	// wait one second to activate the bug
+	PhysicsContext::run_input_instruction(&mut physics,&physics_data,strafesnet_common::instruction::TimedInstruction{
+		time:Time::from_millis(500),
+		instruction:strafesnet_common::physics::Instruction::Idle,
+	});
+
+	Ok(())
+}