Added position

features/src/ray.rs

@@ -1,3 +1,6 @@
+use crate::num_traits_cast;
+use num_traits::NumCast;
+
 use crate::structs::Tuple;
 
 #[derive(Debug, PartialEq)]
@@ -17,6 +20,10 @@ impl Ray {
             })
         }
     }
+
+    fn position<X: NumCast>(&self, time: X) -> Tuple {
+        self.origin + self.direction * num_traits_cast!(time)
+    }
 }
 
 
@@ -49,4 +56,15 @@ mod tests {
         assert_eq!(ray, None);
     }
 
+    #[test]
+    pub fn create_and_query_ray() {
+        let origin = Tuple::point(2, 3, 4);
+        let direction = Tuple::vector(1, 0, 0);
+
+        let ray = Ray::new(origin, direction).unwrap();
+        assert_eq!(Tuple::point(2, 3, 4), ray.position(0));
+        assert_eq!(Tuple::point(3, 3, 4), ray.position(1));
+        assert_eq!(Tuple::point(1, 3, 4), ray.position(-1));
+        assert_eq!(Tuple::point(4.5, 3, 4), ray.position(2.5));
+    }
 }