From 72c6944ab946a1db4d1dafac3f94d393a27663c8 Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Sat, 17 Jul 2021 15:58:57 -0700
Subject: [PATCH] world: implement World::shade_hit.

---
 rtchallenge/src/world.rs | 49 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/rtchallenge/src/world.rs b/rtchallenge/src/world.rs
index 126fd06..4991a2b 100644
--- a/rtchallenge/src/world.rs
+++ b/rtchallenge/src/world.rs
@@ -1,7 +1,7 @@
 use crate::{
-    intersections::Intersections,
+    intersections::{Intersections, PrecomputedData},
     lights::PointLight,
-    materials::Material,
+    materials::{lighting, Material},
     matrices::Matrix4x4,
     rays::Ray,
     spheres::{intersect, Sphere},
@@ -55,6 +55,7 @@ impl World {
     }
 
     /// Intesects the ray with this world.
+    ///
     /// # Examples
     /// ```
     /// use rtchallenge::{rays::Ray, tuples::Tuple, world::World};
@@ -81,4 +82,48 @@ impl World {
         });
         Intersections::new(xs)
     }
+
+    /// Compute shaded value for given precomputation.
+    ///
+    /// # Examples
+    /// ```
+    /// use rtchallenge::{
+    ///     intersections::{prepare_computations, Intersection},
+    ///     lights::PointLight,
+    ///     rays::Ray,
+    ///     tuples::{Color, Tuple},
+    ///     world::World,
+    /// };
+    ///
+    /// // Shading an intersection.
+    /// let w = World::test_world();
+    /// let r = Ray::new(Tuple::point(0., 0., -5.), Tuple::vector(0., 0., 1.));
+    /// let s = &w.objects[0];
+    /// let i = Intersection::new(4., &s);
+    /// let comps = prepare_computations(&i, &r);
+    /// let c = w.shade_hit(&comps);
+    /// assert_eq!(c, Color::new(0.38066, 0.47583, 0.2855));
+    ///
+    /// // Shading an intersection from the inside.
+    /// let mut w = World::test_world();
+    /// w.light = Some(PointLight::new(
+    ///     Tuple::point(0., 0.25, 0.),
+    ///     Color::new(1., 1., 1.),
+    /// ));
+    /// let r = Ray::new(Tuple::point(0., 0., 0.), Tuple::vector(0., 0., 1.));
+    /// let s = &w.objects[1];
+    /// let i = Intersection::new(0.5, &s);
+    /// let comps = prepare_computations(&i, &r);
+    /// let c = w.shade_hit(&comps);
+    /// assert_eq!(c, Color::new(0.90498, 0.90498, 0.90498));
+    /// ```
+    pub fn shade_hit(&self, comps: &PrecomputedData) -> Color {
+        lighting(
+            &comps.object.material,
+            &self.light.as_ref().expect("World has no lights"),
+            comps.point,
+            comps.eyev,
+            comps.normalv,
+        )
+    }
 }