From f44d671573c2f910b6e5eeef7b39cb26e02d98b4 Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Fri, 16 Jul 2021 20:13:20 -0700
Subject: [PATCH] rays: basic ray with construction and position methods

---
 rtchallenge/src/lib.rs  |  1 +
 rtchallenge/src/rays.rs | 43 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 rtchallenge/src/rays.rs

diff --git a/rtchallenge/src/lib.rs b/rtchallenge/src/lib.rs
index 303381b..b443f53 100644
--- a/rtchallenge/src/lib.rs
+++ b/rtchallenge/src/lib.rs
@@ -1,5 +1,6 @@
 pub mod canvas;
 pub mod matrices;
+pub mod rays;
 pub mod tuples;
 
 /// Value considered close enough for PartialEq implementations.
diff --git a/rtchallenge/src/rays.rs b/rtchallenge/src/rays.rs
new file mode 100644
index 0000000..27c401f
--- /dev/null
+++ b/rtchallenge/src/rays.rs
@@ -0,0 +1,43 @@
+use crate::{matrices::Matrix4x4, tuples::Tuple};
+
+pub struct Ray {
+    pub origin: Tuple,
+    pub direction: Tuple,
+}
+
+impl Ray {
+    /// Create a ray with the given origin point and direction vector.
+    /// Will panic if origin not a point or direction not a vector.
+    ///
+    /// # Examples
+    /// ```
+    /// use rtchallenge::{rays::Ray, tuples::Tuple};
+    ///
+    /// let origin = Tuple::point(1., 2., 3.);
+    /// let direction = Tuple::vector(4., 5., 6.);
+    /// let r = Ray::new(origin, direction);
+    /// assert_eq!(r.origin, origin);
+    /// assert_eq!(r.direction, direction);
+    /// ```
+    pub fn new(origin: Tuple, direction: Tuple) -> Ray {
+        assert!(origin.is_point(), "Ray origin must be a point");
+        assert!(direction.is_vector(), "Ray direction must be a vector");
+        Ray { origin, direction }
+    }
+
+    /// Compute a point from the given distance along the `Ray`.
+    ///
+    /// # Examples
+    /// ```
+    /// use rtchallenge::{rays::Ray, tuples::Tuple};
+    ///
+    /// let r = Ray::new(Tuple::point(2., 3., 4.), Tuple::vector(1., 0., 0.));
+    /// assert_eq!(r.position(0.), Tuple::point(2., 3., 4.));
+    /// assert_eq!(r.position(1.), Tuple::point(3., 3., 4.));
+    /// assert_eq!(r.position(-1.), Tuple::point(1., 3., 4.));
+    /// assert_eq!(r.position(2.5), Tuple::point(4.5, 3., 4.));
+    /// ```
+    pub fn position(&self, t: f32) -> Tuple {
+        self.origin + self.direction * t
+    }
+}