1 files changed, 39 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
+    }
+}