From b756cc394acbc03460bce2d8c76c39e4607f94ec Mon Sep 17 00:00:00 2001
From: djairoh <djairoh@mykolab.com>
Date: Thu, 16 Apr 2026 14:04:55 +0200
Subject: [PATCH] ft: 10: metals

---
 Cargo.lock                          | 10 ++++
 Cargo.toml                          |  1 +
 src/camera.rs                       | 15 +++---
 src/main.rs                         | 19 +++++--
 src/objects.rs                      |  1 +
 src/objects/hit.rs                  | 22 ++++++--
 src/objects/materials.rs            |  2 +
 src/objects/materials/lambertian.rs | 79 +++++++++++++++++++++++++++++
 src/objects/materials/traits.rs     |  5 ++
 src/objects/sphere.rs               | 20 ++++++--
 src/ray.rs                          | 12 ++---
 src/vec3.rs                         | 54 ++++++++++++++------
 12 files changed, 199 insertions(+), 41 deletions(-)
 create mode 100644 src/objects/materials.rs
 create mode 100644 src/objects/materials/lambertian.rs
 create mode 100644 src/objects/materials/traits.rs

diff --git a/Cargo.lock b/Cargo.lock
index 31a7e18..936d2e9 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -674,6 +674,15 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "is_close"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4d49e01f14871e71a0dce6f09eb72308bca74a4adb1bab5a8c34ee26979a8a2"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "itertools"
 version = "0.14.0"
@@ -1219,6 +1228,7 @@ name = "raytracing"
 version = "0.1.0"
 dependencies = [
  "image",
+ "is_close",
  "log",
  "ops",
  "pretty_env_logger",
diff --git a/Cargo.toml b/Cargo.toml
index dc98c47..425f8a1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,6 +5,7 @@ edition = "2024"
 
 [dependencies]
 image = "0.25.10"
+is_close = "0.1.3"
 log = "0.4.29"
 ops = "0.6.0"
 pretty_env_logger = "0.5.0"
diff --git a/src/camera.rs b/src/camera.rs
index 15782f2..0047283 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -20,10 +20,7 @@ pub struct Camera {
 }
 
 impl Camera {
-    pub fn new(aspect_ratio: f32, image_width: u32) -> Camera {
-        Camera::new_aa(aspect_ratio, image_width, 1)
-    }
-    pub fn new_aa(aspect_ratio: f32, image_width: u32, anti_alias_rate: u32) -> Camera {
+    pub fn new(aspect_ratio: f32, image_width: u32, anti_alias_rate: u32, max_depth: u32) -> Self {
         let image_height = max(1, (image_width as f32 / aspect_ratio) as u32);
 
         //camera
@@ -42,11 +39,11 @@ impl Camera {
         let pixel00_loc =
             camera_center - Vec3::new(0., 0., focal_length) - viewport_u / 2 - viewport_v / 2;
 
-        Camera {
+        Self {
             image_width: image_width,
             image_height: image_height,
             anti_alias_rate: anti_alias_rate,
-            max_depth: 50,
+            max_depth: max_depth,
             center: camera_center,
             pixel00_loc: pixel00_loc,
             pixel_delta_u: pixel_delta_u,
@@ -93,8 +90,10 @@ impl Camera {
 
         let closest = Hit::hit_list(hittables, r);
         if let Some(hit) = closest {
-            let dir = *hit.n() + Vec3::random_unit_hemisphere(hit.n());
-            return 0.5 * self.ray_colour(hittables, &Ray::new(*hit.p(), dir), depth - 1);
+            if let Some((scattered, att)) = hit.mat().scatter(&hit, r) {
+                return att * self.ray_colour(hittables, &scattered, depth - 1);
+            }
+            return Colour::nil();
         }
 
         // background
diff --git a/src/main.rs b/src/main.rs
index e3ba50d..12af2af 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,7 +5,10 @@ mod objects;
 mod ray;
 mod vec3;
 
+use std::sync::Arc;
+
 use crate::camera::Camera;
+use crate::objects::materials::lambertian::{Lambertian, Metal};
 use crate::objects::sphere::Sphere;
 use crate::ray::Ray;
 use crate::vec3::Vec3;
@@ -15,10 +18,18 @@ fn main() {
     pretty_env_logger::init();
 
     // setup objects
-    let mut world = vec![Sphere::new(Vec3::new(0., 0., -1.), 0.5)];
-    world.push(Sphere::new(Vec3::new(0., 0., -0.1), 0.01));
-    world.push(Sphere::new(Vec3::new(0., -100.5, -1.), 100.));
+    let metal = Arc::new(Metal::rgb(0.7, 0.4, 0.2, 1., 0.1));
+    let ground = Arc::new(Lambertian::rgb(0.8, 0.8, 0., 1.0));
+    let center = Arc::new(Lambertian::rgb(0.1, 0.2, 0.5, 1.));
+    let left = Arc::new(Metal::rgb(0.8, 0.8, 0.8, 1., 0.3));
+    let right = Arc::new(Metal::rgb(0.8, 0.6, 0.2, 1., 1.0));
 
-    let c = Camera::new_aa(16. / 9., 400, 3);
+    let mut world = vec![Sphere::xyz(0., 0.5, -0.8, 0.1, metal.clone())];
+    world.push(Sphere::xyz(0., -100.5, -1., 100., ground.clone()));
+    world.push(Sphere::xyz(0., 0., -1.2, 0.5, center.clone()));
+    world.push(Sphere::xyz(-1., 0., -1.0, 0.5, left.clone()));
+    world.push(Sphere::xyz(1., 0., -1.0, 0.5, right.clone()));
+
+    let c = Camera::new(16. / 9., 800, 2, 50);
     c.render(&world);
 }
diff --git a/src/objects.rs b/src/objects.rs
index b7c1286..be146ee 100644
--- a/src/objects.rs
+++ b/src/objects.rs
@@ -1,3 +1,4 @@
 pub mod hit;
+pub mod materials;
 pub mod sphere;
 pub mod traits;
diff --git a/src/objects/hit.rs b/src/objects/hit.rs
index 529bd58..633510e 100644
--- a/src/objects/hit.rs
+++ b/src/objects/hit.rs
@@ -1,14 +1,26 @@
-use crate::{objects::traits::Hittable, ray::Ray, vec3::Vec3};
+use std::sync::Arc;
+
+use crate::{
+    objects::{materials::traits::Material, traits::Hittable},
+    ray::Ray,
+    vec3::Vec3,
+};
 
 pub struct Hit {
     t: f32,
     p: Vec3,
     n: Vec3,
+    mat: Arc<dyn Material>,
 }
 
 impl Hit {
-    pub fn new(t: f32, p: Vec3, n: Vec3) -> Hit {
-        Hit { t: t, p: p, n: n }
+    pub fn new(t: f32, p: Vec3, n: Vec3, mat: Arc<dyn Material>) -> Self {
+        Self {
+            t: t,
+            p: p,
+            n: n,
+            mat: mat,
+        }
     }
 
     pub fn t(&self) -> &f32 {
@@ -23,6 +35,10 @@ impl Hit {
         &self.n
     }
 
+    pub fn mat(&self) -> Arc<dyn Material> {
+        self.mat.clone()
+    }
+
     pub fn hit_list<T: Hittable>(hittables: &Vec<T>, r: &Ray) -> Option<Hit> {
         let mut closest: Option<Hit> = None;
         for hittable in hittables {
diff --git a/src/objects/materials.rs b/src/objects/materials.rs
new file mode 100644
index 0000000..39a34e0
--- /dev/null
+++ b/src/objects/materials.rs
@@ -0,0 +1,2 @@
+pub mod lambertian;
+pub mod traits;
diff --git a/src/objects/materials/lambertian.rs b/src/objects/materials/lambertian.rs
new file mode 100644
index 0000000..127298e
--- /dev/null
+++ b/src/objects/materials/lambertian.rs
@@ -0,0 +1,79 @@
+use rand::RngExt;
+
+use crate::{
+    objects::{hit::Hit, materials::traits::Material},
+    ray::Ray,
+    vec3::{Colour, Vec3},
+};
+
+pub struct Lambertian {
+    albedo: Colour,
+    prob: f32,
+}
+
+impl Lambertian {
+    pub fn new(albedo: Colour, prob: f32) -> Self {
+        Self {
+            albedo: albedo,
+            prob: prob,
+        }
+    }
+
+    pub fn rgb(r: f32, g: f32, b: f32, prob: f32) -> Self {
+        Self {
+            albedo: Colour::new(r, g, b),
+            prob: prob,
+        }
+    }
+}
+
+impl Material for Lambertian {
+    fn scatter(&self, hit: &Hit, ray: &Ray) -> Option<(Ray, Colour)> {
+        let mut rng = rand::rng();
+        if self.prob >= rng.random::<f32>() {
+            let mut dir = *hit.n() + Vec3::random_unit();
+            if dir.near_zero() {
+                dir = *hit.n();
+            }
+            let scattered = Ray::new(*hit.p(), dir);
+            return Some((scattered, self.albedo));
+        }
+        return None;
+    }
+}
+
+pub struct Metal {
+    albedo: Colour,
+    prob: f32,
+    fuzz: f32,
+}
+
+impl Metal {
+    pub fn new(albedo: Colour, prob: f32, fuzz: f32) -> Self {
+        Self {
+            albedo: albedo,
+            prob: prob,
+            fuzz: fuzz,
+        }
+    }
+
+    pub fn rgb(r: f32, g: f32, b: f32, prob: f32, fuzz: f32) -> Self {
+        Self {
+            albedo: Colour::new(r, g, b),
+            prob: prob,
+            fuzz: fuzz,
+        }
+    }
+}
+
+impl Material for Metal {
+    fn scatter(&self, hit: &Hit, ray: &Ray) -> Option<(Ray, Colour)> {
+        let mut rng = rand::rng();
+        if self.prob >= rng.random::<f32>() {
+            let mut refl = ray.dir().reflect(hit.n());
+            refl = refl.get_unit() + self.fuzz * Vec3::random_unit();
+            return Some((Ray::new(*hit.p(), refl), self.albedo));
+        }
+        return None;
+    }
+}
diff --git a/src/objects/materials/traits.rs b/src/objects/materials/traits.rs
new file mode 100644
index 0000000..a2024ea
--- /dev/null
+++ b/src/objects/materials/traits.rs
@@ -0,0 +1,5 @@
+use crate::{objects::hit::Hit, ray::Ray, vec3::Colour};
+
+pub trait Material {
+    fn scatter(&self, hit: &Hit, ray: &Ray) -> Option<(Ray, Colour)>;
+}
diff --git a/src/objects/sphere.rs b/src/objects/sphere.rs
index ab52fb9..19bdbee 100644
--- a/src/objects/sphere.rs
+++ b/src/objects/sphere.rs
@@ -1,19 +1,31 @@
 use core::f32::math::sqrt;
+use std::sync::Arc;
 
 use crate::objects::hit::Hit;
+use crate::objects::materials::traits::Material;
 use crate::objects::traits::Hittable;
 use crate::Vec3;
 
 pub struct Sphere {
     center: Vec3,
     radius: f32,
+    material: Arc<dyn Material>,
 }
 
 impl Sphere {
-    pub fn new(center: Vec3, radius: f32) -> Sphere {
-        Sphere {
+    pub fn new(center: Vec3, r: f32, mat: Arc<dyn Material>) -> Self {
+        Self {
             center: center,
-            radius: radius,
+            radius: r,
+            material: mat,
+        }
+    }
+
+    pub fn xyz(x: f32, y: f32, z: f32, r: f32, mat: Arc<dyn Material>) -> Self {
+        Self {
+            center: Vec3::new(x, y, z),
+            radius: r,
+            material: mat,
         }
     }
 }
@@ -31,7 +43,7 @@ impl Hittable for Sphere {
         } else {
             let t = (h - sqrt(d)) / a;
             let p = r.at(t);
-            Some(Hit::new(t, p, self.normal_at(&p)))
+            Some(Hit::new(t, p, self.normal_at(&p), self.material.clone()))
         }
     }
 
diff --git a/src/ray.rs b/src/ray.rs
index 80f23da..7cfea1e 100644
--- a/src/ray.rs
+++ b/src/ray.rs
@@ -6,17 +6,17 @@ pub struct Ray {
 }
 
 impl Ray {
-    pub fn at(&self, t: f32) -> Vec3 {
-        self.origin + t * self.dir
-    }
-
-    pub fn new(origin: Vec3, dir: Vec3) -> Ray {
-        Ray {
+    pub fn new(origin: Vec3, dir: Vec3) -> Self {
+        Self {
             origin: origin,
             dir: dir,
         }
     }
 
+    pub fn at(&self, t: f32) -> Vec3 {
+        self.origin + t * self.dir
+    }
+
     pub fn origin(&self) -> &Vec3 {
         &self.origin
     }
diff --git a/src/vec3.rs b/src/vec3.rs
index a1b3a15..6b355b9 100644
--- a/src/vec3.rs
+++ b/src/vec3.rs
@@ -1,11 +1,11 @@
 use core::f32::math::sqrt;
+use is_close::default;
+use rand::RngExt;
 use std::{
     fmt::Display,
     ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign},
 };
 
-use rand::RngExt;
-
 #[derive(Copy, Clone)]
 pub struct Vec3 {
     r: f32,
@@ -16,11 +16,11 @@ pub struct Vec3 {
 pub type Colour = Vec3;
 
 impl Vec3 {
-    pub fn new(r: f32, g: f32, b: f32) -> Vec3 {
+    pub fn new(r: f32, g: f32, b: f32) -> Self {
         Self { r: r, g: g, b: b }
     }
 
-    pub fn nil() -> Vec3 {
+    pub fn nil() -> Self {
         Self {
             r: 0.,
             g: 0.,
@@ -28,26 +28,26 @@ impl Vec3 {
         }
     }
 
-    pub fn random() -> Vec3 {
+    pub fn random() -> Self {
         let mut rng = rand::rng();
-        Vec3 {
+        Self {
             r: rng.random_range(-1.0..1.),
             g: rng.random_range(-1.0..1.),
             b: rng.random_range(-1.0..1.),
         }
     }
 
-    pub fn random_unit() -> Vec3 {
+    pub fn random_unit() -> Self {
         loop {
-            let v = Vec3::random();
+            let v = Self::random();
             if v.length_squared() <= 1. {
                 return v / v.length();
             }
         }
     }
 
-    pub fn random_unit_hemisphere(n: &Vec3) -> Vec3 {
-        let v = Vec3::random_unit();
+    pub fn random_unit_hemisphere(n: &Self) -> Self {
+        let v = Self::random_unit();
         if n.dot(&v) > 0.0 {
             v
         } else {
@@ -75,12 +75,12 @@ impl Vec3 {
         (self.r * self.r + self.g * self.g + self.b * self.b) as f32
     }
 
-    pub fn dot(&self, other: &Vec3) -> f32 {
+    pub fn dot(&self, other: &Self) -> f32 {
         self.r * other.r + self.g * other.g + self.b * other.b
     }
 
-    pub fn cross(&self, other: &Vec3) -> Vec3 {
-        Vec3 {
+    pub fn cross(&self, other: &Self) -> Self {
+        Self {
             r: self.g * other.b - self.b * other.g,
             g: self.b * other.r - self.r * other.b,
             b: self.r * other.g - self.g * other.r,
@@ -91,10 +91,20 @@ impl Vec3 {
         self /= self.length();
     }
 
-    pub fn get_unit(self) -> Vec3 {
+    pub fn get_unit(self) -> Self {
         self / self.length()
     }
 
+    pub fn near_zero(&self) -> bool {
+        default().is_close(self.r, 0.)
+            && default().is_close(self.g, 0.)
+            && default().is_close(self.b, 0.)
+    }
+
+    pub fn reflect(&self, o: &Vec3) -> Vec3 {
+        *self - 2. * self.dot(o) * o
+    }
+
     pub fn output(self) -> image::Rgb<u8> {
         // gamma correction
         let r = if self.r > 0. {
@@ -120,8 +130,8 @@ impl Vec3 {
         image::Rgb([ir, ig, ib])
     }
 
-    pub fn clone(&self) -> Vec3 {
-        Vec3 {
+    pub fn clone(&self) -> Self {
+        Self {
             r: self.r,
             g: self.g,
             b: self.b,
@@ -289,6 +299,18 @@ impl Mul<Vec3> for f32 {
     }
 }
 
+impl Mul<&Vec3> for f32 {
+    type Output = Vec3;
+
+    fn mul(self, rhs: &Vec3) -> Self::Output {
+        Vec3 {
+            r: rhs.r * self,
+            g: rhs.g * self,
+            b: rhs.b * self,
+        }
+    }
+}
+
 impl MulAssign<Vec3> for Vec3 {
     fn mul_assign(&mut self, rhs: Self) {
         *self = Self {