ft: 5,6.1: sphere class + normals

src/objects/traits.rs

@@ -0,0 +1,11 @@
+use crate::objects::hit::Hit;
+use crate::Ray;
+use crate::Vec3;
+
+pub trait Hittable {
+    fn hit(&self, r: &Ray) -> Option<Hit>;
+}
+
+pub trait Normal {
+    fn normal_at(&self, p: &Vec3) -> Vec3;
+}