6 files changed, 174 insertions, 0 deletions
diff --git a/src/material/dielectric.rs b/src/material/dielectric.rs
new file mode 100644
index 0000000..bcacb78
--- /dev/null
+++ b/src/material/dielectric.rs
@@ -0,0 +1,39 @@
+use super::Material;
+use crate::{hittable::HitRecord, vec3::Vec3};
+use crate::vec3::Color;
+use crate::ray::Ray;
+
+pub struct Dielectric {
+    pub index_of_refraction: f64,
+}
+
+impl Dielectric {
+    fn reflectance(cosine: f64, ref_idx: f64) -> f64 {
+        // Using Schlick's Approximation:
+        let mut r0 = (1.0 - ref_idx) / (1.0 + ref_idx);
+        r0 *= r0;
+        r0 + (1.0 - r0) * (1.0 - cosine).powi(5)
+    }
+}
+
+impl Material for Dielectric {
+    fn scatter(&self, ray_in: &Ray, hit_record: &HitRecord, attenuation: &mut Color, scattered: &mut Ray) -> bool {
+        *attenuation = Color { x: 1.0, y: 1.0, z: 1.0 };
+        let refraction_ratio = if hit_record.front_face { 1.0 / self.index_of_refraction } else { self.index_of_refraction };
+        let unit_direction = ray_in.direction.unit_vector();
+        let cos_theta = hit_record.normal.dot(&-&unit_direction).min(1.0);
+        let sin_theta = (1.0 - cos_theta * cos_theta).sqrt();
+
+        let cannot_refract = refraction_ratio * sin_theta > 1.0;
+        let direction: Vec3;
+
+        if cannot_refract || Self::reflectance(cos_theta, refraction_ratio) > rand::random::<f64>() {
+            direction = unit_direction.reflect(&hit_record.normal)
+        } else {
+            direction = unit_direction.refract(&hit_record.normal, refraction_ratio)
+        }
+
+        *scattered = Ray { origin: hit_record.p.clone(), direction, time: ray_in.time };
+        true
+    }
+}
diff --git a/src/material/diffuse_light.rs b/src/material/diffuse_light.rs
new file mode 100644
index 0000000..fecbcff
--- /dev/null
+++ b/src/material/diffuse_light.rs
@@ -0,0 +1,29 @@
+use std::sync::Arc;
+
+use super::Material;
+use crate::{hittable::HitRecord, texture::Texture, vec3::Point3};
+use crate::vec3::Color;
+use crate::texture::SolidColor;
+use crate::ray::Ray;
+
+pub struct DiffuseLight {
+    emit: Arc<dyn Texture>,
+}
+
+impl DiffuseLight {
+    pub fn from_color(color: Color) -> Self {
+        Self {
+            emit: Arc::new(SolidColor::from_color(color)),
+        }
+    }
+}
+
+impl Material for DiffuseLight {
+    fn scatter(&self, _: &Ray, _: &HitRecord, _: &mut Color, _: &mut Ray) -> bool {
+        false
+    }
+
+    fn emitted(&self, u: f64, v: f64, point: &Point3) -> Color {
+        self.emit.value(u, v, point)
+    }
+}
diff --git a/src/material/isotropic.rs b/src/material/isotropic.rs
new file mode 100644
index 0000000..f59fa7d
--- /dev/null
+++ b/src/material/isotropic.rs
@@ -0,0 +1,33 @@
+use std::sync::Arc;
+
+use super::Material;
+use crate::{hittable::HitRecord, texture::Texture, vec3::Vec3};
+use crate::vec3::Color;
+use crate::texture::SolidColor;
+use crate::ray::Ray;
+
+pub struct Isotropic {
+    albedo: Arc<dyn Texture>,
+}
+
+impl Isotropic {
+    pub fn from_color(color: Color) -> Self {
+        Self {
+            albedo: Arc::new(SolidColor::from_color(color)),
+        }
+    }
+
+    pub fn from_texture(texture: Arc<dyn Texture>) -> Self {
+        Self {
+            albedo: texture,
+        }
+    }
+}
+
+impl Material for Isotropic {
+    fn scatter(&self, ray_in: &Ray, hit_record: &HitRecord, attenuation: &mut Color, scattered: &mut Ray) -> bool {
+        *scattered = Ray { origin: hit_record.p.clone(), direction: Vec3::random_in_unit_sphere(), time: ray_in.time };
+        *attenuation = self.albedo.value(hit_record.u, hit_record.v, &hit_record.p);
+        true
+    }
+}
diff --git a/src/material/lambertian.rs b/src/material/lambertian.rs
new file mode 100644
index 0000000..95f698e
--- /dev/null
+++ b/src/material/lambertian.rs
@@ -0,0 +1,34 @@
+use std::sync::Arc;
+
+use super::Material;
+use crate::{hittable::HitRecord, texture::Texture, vec3::Vec3};
+use crate::vec3::Color;
+use crate::texture::SolidColor;
+use crate::ray::Ray;
+
+pub struct Lambertian {
+    pub albedo: Arc<dyn Texture>,
+}
+
+impl Lambertian {
+    pub fn from_color(color: Color) -> Self {
+        Self {
+            albedo: Arc::new(SolidColor { color_value: color.clone() }),
+        }
+    }
+}
+
+impl Material for Lambertian {
+    fn scatter(&self, ray_in : &Ray, hit_record: &HitRecord, attenuation: &mut Color, scattered: &mut Ray) -> bool {
+        let mut scatter_direction = &hit_record.normal + Vec3::random_unit_vector();
+
+        // Catch zero-vector scatter directions that will generate issues later
+        if scatter_direction.near_zero() {
+            scatter_direction = hit_record.normal.clone();
+        }
+
+        *scattered = Ray { origin: hit_record.p.clone(), direction: scatter_direction, time: ray_in.time };
+        *attenuation = self.albedo.value(hit_record.u, hit_record.v, &hit_record.p);
+        true
+    }
+}
diff --git a/src/material/metal.rs b/src/material/metal.rs
new file mode 100644
index 0000000..2865a2f
--- /dev/null
+++ b/src/material/metal.rs
@@ -0,0 +1,18 @@
+use super::Material;
+use crate::{hittable::HitRecord, vec3::Vec3};
+use crate::vec3::Color;
+use crate::ray::Ray;
+
+pub struct Metal {
+    pub albedo: Color,
+    pub fuzz: f64, // TODO: This should have value 0.0 - 1.0; this is not enforced
+}
+
+impl Material for Metal {
+    fn scatter(&self, ray_in: &Ray, hit_record: &HitRecord, attenuation: &mut Color, scattered: &mut Ray) -> bool {
+        let reflected = ray_in.direction.unit_vector().reflect(&hit_record.normal);
+        *scattered = Ray { origin: hit_record.p.clone(), direction: reflected + self.fuzz * Vec3::random_in_unit_sphere(), time: ray_in.time };
+        *attenuation = self.albedo.clone();
+        scattered.direction.dot(&hit_record.normal) > 0.0
+    }
+}
diff --git a/src/material/mod.rs b/src/material/mod.rs
new file mode 100644
index 0000000..bf1eb24
--- /dev/null
+++ b/src/material/mod.rs
@@ -0,0 +1,21 @@
+mod lambertian;
+pub use lambertian::Lambertian;
+mod metal;
+pub use metal::Metal;
+mod dielectric;
+pub use dielectric::Dielectric;
+mod diffuse_light;
+pub use diffuse_light::DiffuseLight;
+mod isotropic;
+pub use isotropic::Isotropic;
+
+use crate::{hittable::HitRecord, vec3::Point3};
+use crate::vec3::Color;
+use crate::ray::Ray;
+
+pub trait Material: Send + Sync {
+    fn emitted(&self, _: f64, _: f64, _: &Point3) -> Color {
+        Color { x: 0.0, y: 0.0, z: 0.0 }    
+    }
+    fn scatter(&self, ray_in: &Ray, hit_record: &HitRecord, attenuation: &mut Color, scattered: &mut Ray) -> bool;
+}