Link to educational material and fixes on comments (#198)

* Fix comments in point_composite_shape test

* Add a link to educational material

crates/parry2d/tests/query/point_composite_shape.rs

@@ -37,7 +37,7 @@ fn project_local_point_and_get_feature_projects_correctly_from_outside() {
     let mesh = TriMesh::new(vertices, vec![[0, 1, 2], [3, 0, 2]]);
 
     {
-        let query_pt = Point2::new(-1.0, 0.0); // Inside the top-right triangle (index 1)
+        let query_pt = Point2::new(-1.0, 0.0); // Left from the bottom-left triangle (index 0)
 
         let (proj, feat) = mesh.project_local_point_and_get_feature(&query_pt);
 
@@ -52,7 +52,7 @@ fn project_local_point_and_get_feature_projects_correctly_from_outside() {
         assert_eq!(feat.unwrap_face(), correct_tri_idx);
     }
     {
-        let query_pt = Point2::new(0.5, 2.0); // Inside the top-right triangle (index 1)
+        let query_pt = Point2::new(0.5, 2.0); // Above the top-right triangle (index 1)
 
         let (proj, feat) = mesh.project_local_point_and_get_feature(&query_pt);
 

src/query/point/point_triangle.rs

@@ -60,6 +60,9 @@ impl PointQueryWithLocation for Triangle {
         pt: &Point<Real>,
         solid: bool,
     ) -> (PointProjection, Self::Location) {
+        // To understand the ideas, consider reading the slides below
+        // https://box2d.org/files/ErinCatto_GJK_GDC2010.pdf
+
         let a = self.a;
         let b = self.b;
         let c = self.c;