wip: normal material

src/objects/hit.rs

@@ -45,6 +45,7 @@ impl Hit {
         self.front_face
     }
 
+    // TODO: use front_face to discard back-hits for culling
     pub fn hit_list(hittables: &Vec<Arc<dyn Hittable>>, r: &Ray) -> Option<Hit> {
         let mut closest: Option<Hit> = None;
         for hittable in hittables {