From c9b42d94b35b926da2daefce07f6a77dbf8155dc Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Fri, 16 Jul 2021 21:14:23 -0700
Subject: [PATCH] intersections: now store object in Intersection.

---
 rtchallenge/src/intersections.rs | 11 ++++++++++-
 rtchallenge/src/spheres.rs       | 23 +++++++++++++++++------
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/rtchallenge/src/intersections.rs b/rtchallenge/src/intersections.rs
index 9e8bba6..72bf17c 100644
--- a/rtchallenge/src/intersections.rs
+++ b/rtchallenge/src/intersections.rs
@@ -2,6 +2,7 @@ use std::ops::Index;
 
 use crate::spheres::Sphere;
 
+#[derive(Debug, PartialEq)]
 pub struct Intersection<'i> {
     pub t: f32,
     pub object: &'i Sphere,
@@ -31,7 +32,9 @@ impl<'i> Intersection<'i> {
 /// ```
 /// use rtchallenge::{
 ///     intersections::{Intersection, Intersections},
-///     spheres::Sphere,
+///     rays::Ray,
+///     spheres::{intersect, Sphere},
+///     tuples::Tuple,
 /// };
 ///
 /// let s = Sphere::default();
@@ -41,6 +44,12 @@ impl<'i> Intersection<'i> {
 /// assert_eq!(xs.len(), 2);
 /// assert_eq!(xs[0].t, 1.);
 /// assert_eq!(xs[1].t, 2.);
+///
+/// let r = Ray::new(Tuple::point(0., 0., -5.), Tuple::vector(0., 0., 1.));
+/// let xs = intersect(&s, &r);
+/// assert_eq!(xs.len(), 2);
+/// assert_eq!(xs[0].object, &s);
+/// assert_eq!(xs[1].object, &s);
 /// ```
 pub struct Intersections<'i>(Vec<Intersection<'i>>);
 
diff --git a/rtchallenge/src/spheres.rs b/rtchallenge/src/spheres.rs
index 7568ebd..cf16436 100644
--- a/rtchallenge/src/spheres.rs
+++ b/rtchallenge/src/spheres.rs
@@ -1,4 +1,5 @@
 use crate::{
+    intersections::Intersection,
     rays::Ray,
     tuples::{dot, Tuple},
 };
@@ -12,6 +13,7 @@ pub struct Sphere {}
 /// # Examples
 /// ```
 /// use rtchallenge::{
+///     intersections::Intersection,
 ///     rays::Ray,
 ///     spheres::{intersect, Sphere},
 ///     tuples::Tuple,
@@ -21,7 +23,10 @@ pub struct Sphere {}
 /// let r = Ray::new(Tuple::point(0., 0., -5.), Tuple::vector(0., 0., 1.));
 /// let s = Sphere::default();
 /// let xs = intersect(&s, &r);
-/// assert_eq!(xs, vec![4., 6.]);
+/// assert_eq!(
+///     xs,
+///     vec![Intersection::new(4., &s), Intersection::new(6., &s)]
+/// );
 ///
 /// // A ray intersects a sphere at a tangent.
 /// let r = Ray::new(Tuple::point(0., 2., -5.), Tuple::vector(0., 0., 1.));
@@ -33,15 +38,21 @@ pub struct Sphere {}
 /// let r = Ray::new(Tuple::point(0., 0., 0.), Tuple::vector(0., 0., 1.));
 /// let s = Sphere::default();
 /// let xs = intersect(&s, &r);
-/// assert_eq!(xs, vec![-1., 1.]);
+/// assert_eq!(
+///     xs,
+///     vec![Intersection::new(-1., &s), Intersection::new(1., &s)]
+/// );
 ///
 /// // A sphere is behind a ray.
 /// let r = Ray::new(Tuple::point(0., 0., 5.), Tuple::vector(0., 0., 1.));
 /// let s = Sphere::default();
 /// let xs = intersect(&s, &r);
-/// assert_eq!(xs, vec![-6., -4.]);
+/// assert_eq!(
+///     xs,
+///     vec![Intersection::new(-6., &s), Intersection::new(-4., &s)]
+/// );
 /// ```
-pub fn intersect(_sphere: &Sphere, ray: &Ray) -> Vec<f32> {
+pub fn intersect<'s>(sphere: &'s Sphere, ray: &Ray) -> Vec<Intersection<'s>> {
     let sphere_to_ray = ray.origin - Tuple::point(0., 0., 0.);
     let a = dot(ray.direction, ray.direction);
     let b = 2. * dot(ray.direction, sphere_to_ray);
@@ -51,8 +62,8 @@ pub fn intersect(_sphere: &Sphere, ray: &Ray) -> Vec<f32> {
         vec![]
     } else {
         vec![
-            (-b - discriminant.sqrt()) / (2. * a),
-            (-b + discriminant.sqrt()) / (2. * a),
+            Intersection::new((-b - discriminant.sqrt()) / (2. * a), &sphere),
+            Intersection::new((-b + discriminant.sqrt()) / (2. * a), &sphere),
         ]
     }
 }