From 1065702a5d80123f4a64b70ca01a74f522c57b7a Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Sun, 18 Jul 2021 12:46:49 -0700
Subject: [PATCH] materials: make lighting calculation shadow aware

---
 rtchallenge/examples/eoc6.rs |  4 ++--
 rtchallenge/src/materials.rs | 26 ++++++++++++++++++++------
 rtchallenge/src/world.rs     |  2 ++
 3 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/rtchallenge/examples/eoc6.rs b/rtchallenge/examples/eoc6.rs
index 28043a8..959c22f 100644
--- a/rtchallenge/examples/eoc6.rs
+++ b/rtchallenge/examples/eoc6.rs
@@ -31,7 +31,7 @@ fn main() -> Result<()> {
     let light_position = Tuple::point(-10., 10., -10.);
     let light_color = WHITE;
     let light = PointLight::new(light_position, light_color);
-
+    let in_shadow = false;
     for y in 0..h {
         let world_y = half - pixel_size * y as f32;
         for x in 0..w {
@@ -44,7 +44,7 @@ fn main() -> Result<()> {
                 let point = r.position(hit.t);
                 let normal = hit.object.normal_at(point);
                 let eye = -r.direction;
-                let color = lighting(&hit.object.material, &light, point, eye, normal);
+                let color = lighting(&hit.object.material, &light, point, eye, normal, in_shadow);
                 c.set(x, y, color);
             }
         }
diff --git a/rtchallenge/src/materials.rs b/rtchallenge/src/materials.rs
index 9b76a33..671bf08 100644
--- a/rtchallenge/src/materials.rs
+++ b/rtchallenge/src/materials.rs
@@ -54,6 +54,7 @@ impl Default for Material {
 ///     WHITE,
 /// };
 ///
+/// let in_shadow = false;
 /// let m = Material::default();
 /// let position = Tuple::point(0., 0., 0.);
 ///
@@ -61,35 +62,43 @@ impl Default for Material {
 /// let eyev = Tuple::vector(0., 0., -1.);
 /// let normalv = Tuple::vector(0., 0., -1.);
 /// let light = PointLight::new(Tuple::point(0., 0., -10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv);
+/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, Color::new(1.9, 1.9, 1.9));
 ///
 /// // Lighting with the eye between the light and the surface, eye offset 45°.
 /// let eyev = Tuple::vector(0., 2_f32.sqrt() / 2., -2_f32.sqrt() / 2.);
 /// let normalv = Tuple::vector(0., 0., -1.);
 /// let light = PointLight::new(Tuple::point(0., 0., -10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv);
+/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, WHITE);
 ///
 /// // Lighting with the eye opposite surface, light offset 45°.
 /// let eyev = Tuple::vector(0., 0., -1.);
 /// let normalv = Tuple::vector(0., 0., -1.);
 /// let light = PointLight::new(Tuple::point(0., 10., -10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv);
+/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, Color::new(0.7364, 0.7364, 0.7364));
 ///
 /// // Lighting with the eye in the path of the reflection vector.
 /// let eyev = Tuple::vector(0., -2_f32.sqrt() / 2., -2_f32.sqrt() / 2.);
 /// let normalv = Tuple::vector(0., 0., -1.);
 /// let light = PointLight::new(Tuple::point(0., 10., -10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv);
+/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, Color::new(1.6363853, 1.6363853, 1.6363853));
 ///
 /// // Lighting with the light behind the surface.
 /// let eyev = Tuple::vector(0., 0., -1.);
 /// let normalv = Tuple::vector(0., 0., -1.);
 /// let light = PointLight::new(Tuple::point(0., 0., 10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv);
+/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
+/// assert_eq!(result, Color::new(0.1, 0.1, 0.1));
+///
+/// // Lighting with the surface in shadow.
+/// let in_shadow = true;
+/// let eyev = Tuple::vector(0., 0., -1.);
+/// let normalv = Tuple::vector(0., 0., -1.);
+/// let light = PointLight::new(Tuple::point(0., 0., -10.), WHITE);
+/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, Color::new(0.1, 0.1, 0.1));
 /// ```
 pub fn lighting(
@@ -98,6 +107,7 @@ pub fn lighting(
     point: Tuple,
     eyev: Tuple,
     normalv: Tuple,
+    in_shadow: bool,
 ) -> Color {
     // Combine the surface color with the light's color.
     let effective_color = material.color * light.intensity;
@@ -128,5 +138,9 @@ pub fn lighting(
         };
         (diffuse, specular)
     };
-    ambient + diffuse + specular
+    if in_shadow {
+        ambient
+    } else {
+        ambient + diffuse + specular
+    }
 }
diff --git a/rtchallenge/src/world.rs b/rtchallenge/src/world.rs
index 13a875e..121e737 100644
--- a/rtchallenge/src/world.rs
+++ b/rtchallenge/src/world.rs
@@ -119,12 +119,14 @@ impl World {
     pub fn shade_hit(&self, comps: &PrecomputedData) -> Color {
         // TODO(wathiede): support multiple light sources by iterating over all
         // the light sources and summing the calls to lighting.
+        let in_shadow = false;
         lighting(
             &comps.object.material,
             &self.light.as_ref().expect("World has no lights"),
             comps.point,
             comps.eyev,
             comps.normalv,
+            in_shadow,
         )
     }
     /// Compute color for given ray fired at the world.