Revert "det unused"

This reverts commit 6b897620e9.

src/model_physics.rs

@@ -452,11 +452,13 @@ impl MeshQuery<SubmeshFaceId,SubmeshDirectedEdgeId,SubmeshVertId> for PhysicsMes
 pub struct PhysicsMeshTransform{
 	pub vertex:integer::Planar64Affine3,
 	pub normal:integer::mat3::Matrix3<Fixed<2,64>>,
+	pub det:Fixed<3,96>,
 }
 impl PhysicsMeshTransform{
 	pub fn new(transform:integer::Planar64Affine3)->Self{
 		Self{
 			normal:transform.matrix3.adjugate().transpose(),
+			det:transform.matrix3.det(),
 			vertex:transform,
 		}
 	}