3 files changed, 41 insertions(+), 16 deletions(-)

M src/hittable.rs
M src/main.rs
M src/sphere.rs

@@ 1,11 1,23 @@
-use crate::vec3::*;
 use crate::ray::*;
+use crate::vec3::*;
 
 #[derive(Debug, Clone, Copy, Default)]
 pub struct HitRecord {
     pub p: Point3,
     pub normal: Vec3,
     pub t: f64,
+    pub front_face: bool,
+}
+
+impl HitRecord {
+    pub fn set_face_normal(&mut self, r: &Ray, outward_normal: &Vec3) {
+        self.front_face = dot(&r.direction(), outward_normal) < 0.0;
+        self.normal = if self.front_face {
+            *outward_normal
+        } else {
+            -outward_normal
+        };
+    }
 }
 
 pub trait Hittable {

@@ 14,14 14,13 @@ fn hit_sphere(center: &Point3, radius: f64, r: &Ray) -> f64 {
     let oc = r.origin() - *center;
     let a = r.direction().length_squared();
     let half_b = dot(&oc, &r.direction());
-    let c = oc.length_squared() - radius*radius;
-    let discriminant = half_b*half_b - a*c;
-
+    let c = oc.length_squared() - radius * radius;
+    let discriminant = half_b * half_b - a * c;
 
     if discriminant < 0.0 {
         -1.0
     } else {
-        (-half_b - discriminant.sqrt() ) / a
+        (-half_b - discriminant.sqrt()) / a
     }
 }
 


@@ 29,7 28,7 @@ fn ray_color(r: &Ray) -> Color {
     let t = hit_sphere(&Point3::new(0.0, 0.0, -1f64), 0.5, r);
     if t > 0.0 {
         let N = unit_vector(r.at(t) - Vec3::new(0.0, 0.0, -1.0));
-        return 0.5*Color::new(N.x()+1.0, N.y()+1.0, N.z()+1.0);
+        return 0.5 * Color::new(N.x() + 1.0, N.y() + 1.0, N.z() + 1.0);
     }
     let unit_direction = unit_vector(r.direction());
     let t = 0.5 * (unit_direction.y() + 1.0);


@@ 69,7 68,7 @@ fn main() {
             let v = j as f64 / (image_height - 1) as f64;
             let r = Ray::new(
                 &origin,
-                &(lower_left_corner + u * horizontal + v * vertical - origin)
+                &(lower_left_corner + u * horizontal + v * vertical - origin),
             );
             let pixel_color = ray_color(&r);
             write_color(&mut handle, pixel_color);

@@ 1,6 1,6 @@
-use crate::vec3::*;
-use crate::ray::*;
 use crate::hittable::*;
+use crate::ray::*;
+use crate::vec3::*;
 
 #[derive(Debug, Clone, Copy, Default)]
 pub struct Sphere {


@@ 10,7 10,7 @@ pub struct Sphere {
 
 impl Sphere {
     fn new(center: Point3, radius: f64) -> Self {
-        Self{center, radius}
+        Self { center, radius }
     }
 }
 


@@ 19,8 19,8 @@ impl Hittable for Sphere {
         let oc = r.origin() - self.center;
         let a = r.direction().length_squared();
         let half_b = dot(&oc, &r.direction());
-        let c = oc.length_squared() - self.radius*self.radius;
-        let discriminant = half_b*half_b - a*c;
+        let c = oc.length_squared() - self.radius * self.radius;
+        let discriminant = half_b * half_b - a * c;
 
         if discriminant > 0.0 {
             let root = discriminant.sqrt();


@@ 29,16 29,30 @@ impl Hittable for Sphere {
             if temp < t_max && temp > t_min {
                 let t = temp;
                 let p = r.at(t);
-                let normal = (p - self.center) / self.radius;
-                return Some(HitRecord{t, p, normal})
+                let mut rec = HitRecord {
+                    t: temp,
+                    p,
+                    normal: (p - self.center) / self.radius,
+                    front_face: false,
+                };
+                let outward_normal = (rec.p - self.center) / self.radius;
+                rec.set_face_normal(r, &outward_normal);
+                return Some(rec);
             }
 
             let temp = (-half_b + root) / a;
             if temp < t_max && temp > t_min {
                 let t = temp;
                 let p = r.at(t);
-                let normal = (p - self.center) / self.radius;
-                return Some(HitRecord{t, p, normal})
+                let mut rec = HitRecord {
+                    t: temp,
+                    p,
+                    normal: (p - self.center) / self.radius,
+                    front_face: false,
+                };
+                let outward_normal = (rec.p - self.center) / self.radius;
+                rec.set_face_normal(r, &outward_normal);
+                return Some(rec);
             }
         }