upd transparent material

3 files changed, 60 insertions, 12 deletions

diff --git a/src/calculus.rs b/src/calculus.rs
index 568eb60..2e8a1d5 100644
--- a/src/calculus.rs
+++ b/src/calculus.rs
@@ -119,6 +119,19 @@ pub mod calculus {
                 )
             )
         }
+
+        pub fn refract(&self, normal: &Self, etai_over_etat: f32) -> Self {
+            let cos_theta = f32::min(
+                1.0,
+                self.scalar_mul(-1.0).dot_prod(&normal)
+            );
+            let r_out_perp = self
+                .add(&normal.scalar_mul(cos_theta))
+                .scalar_mul(etai_over_etat);
+            let f = (1.0 - r_out_perp.mag_sqr()).abs().sqrt();
+            let r_out_parallel = normal.scalar_mul(-1.0 * f);
+            r_out_perp.add(&r_out_parallel)
+        }
     }
 
     pub struct Ray {
@@ -133,7 +146,13 @@ pub mod calculus {
         }
 
         pub fn reflect(&self, normal: &Vec3) -> Vec3 {
-            self.direction.reflect(&normal)
+            // return unit direction vector
+            self.direction.reflect(&normal).unit()
+        }
+
+        pub fn refract(&self, normal: &Vec3, etai_over_etat: f32) -> Vec3 {
+            // return unit direction vector
+            self.direction.unit().refract(&normal, etai_over_etat)
         }
     }
 
diff --git a/src/main.rs b/src/main.rs
index cc5d6b6..5772ffb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -18,21 +18,23 @@ fn main() {
     let mut world = HittableList::new();
 
     let ground = Material::new(Color::from_name(ColorName::Maroon), MaterialType::Diffuse);
-    let blue = Material::new(Color::new(0.1, 0.2, 0.5), MaterialType::Diffuse);
-    let steel = Material::new(Color::from_name(ColorName::Silver), MaterialType::Metal(0.1));
-    let gold = Material::new(Color::from_name(ColorName::Yellow), MaterialType::Metal(0.0));
+    let stone = Material::new(Color::from_name(ColorName::Gray), MaterialType::Diffuse);
+    let steel = Material::new(Color::from_name(ColorName::Silver), MaterialType::Metallic(0.1));
+    // let gold = Material::new(Color::from_name(ColorName::Yellow), MaterialType::Metallic(0.0));
+    let glass = Material::new(Color::from_name(ColorName::White), MaterialType::Transparent(1.5));
+    let bubble = Material::new(Color::from_name(ColorName::White), MaterialType::Transparent(1.0 / 1.3));
 
     world.push(
         Sphere::new(Point3::new(0.0, -100.5, -1.0), 100.0, ground)
     );
     world.push(
-        Sphere::new(Point3::new(0.0, 0.0, -1.2), 0.5, blue)
+        Sphere::new(Point3::new(0.0, 0.0, -1.2), 0.5, stone)
     );
     world.push(
-        Sphere::new(Point3::new(-1.0, 0.0, -1.0), 0.5, steel)
+        Sphere::new(Point3::new(-1.0, 0.0, -1.0), 0.5, glass)
     );
     world.push(
-        Sphere::new(Point3::new(1.0, 0.0, -1.0), 0.5, gold)
+        Sphere::new(Point3::new(1.0, 0.0, -1.0), 0.5, steel)
     );
 
     let camera = Camera::new();
diff --git a/src/material.rs b/src/material.rs
index a654f4d..833ef19 100644
--- a/src/material.rs
+++ b/src/material.rs
@@ -1,3 +1,4 @@
+use rand::Rng;
 use crate::calculus::calculus::{Ray, Vec3};
 use crate::common::Color;
 use crate::object::HitRecord;
@@ -5,7 +6,8 @@ use crate::object::HitRecord;
 #[derive(Clone)]
 pub enum MaterialType {
     Diffuse,
-    Metal(f32), // color fuzz
+    Metallic(f32), // fuzz
+    Transparent(f32), // refraction index
 }
 
 #[derive(Clone)]
@@ -17,9 +19,9 @@ pub struct Material {
 impl Material {
     pub fn new(albedo: Color, material_type: MaterialType) -> Self {
         let mut material_type = material_type;
-        if let MaterialType::Metal(fuzz) = material_type {
+        if let MaterialType::Metallic(fuzz) = material_type {
             let fuzz = if fuzz <  1.0 { fuzz } else { fuzz };
-            material_type = MaterialType::Metal(fuzz);
+            material_type = MaterialType::Metallic(fuzz);
         }
         Self { albedo, material_type }
     }
@@ -34,11 +36,30 @@ impl Material {
                     scatter_direction
                 }
             }
-            MaterialType::Metal(fuzz) => {
+            MaterialType::Metallic(fuzz) => {
                 let mut reflected = r_in.reflect(&rec.normal);
-                reflected.unit().add(&Vec3::random_unit().scalar_mul(fuzz))
+                reflected.add(&Vec3::random_unit().scalar_mul(fuzz))
 
             }
+            MaterialType::Transparent(refraction_index) => {
+                let ri = if rec.front_face {
+                    1.0 / refraction_index
+                } else {
+                    refraction_index
+                };
+                let cos_theta = f32::min(
+                    r_in.direction.unit().scalar_mul(-1.0).dot_prod(&rec.normal),
+                    1.0
+                );
+                let sin_theta = (1.0 - cos_theta * cos_theta).sqrt();
+                let cannot_refract = ri * sin_theta > 1.0;
+                let random: f32 = rand::rng().random();
+                if cannot_refract || Self::reflectance(cos_theta, ri) > random {
+                    r_in.direction.unit().reflect(&rec.normal)
+                } else {
+                    r_in.refract(&rec.normal, ri)
+                }
+            }
         };
         scattered.origin = rec.position;
         attenuation.r = self.albedo.r;
@@ -46,4 +67,10 @@ impl Material {
         attenuation.b = self.albedo.b;
         true
     }
+
+    fn reflectance(cosine: f32, refraction_index: f32) -> f32 {
+        let mut r0 = (1.0 - refraction_index) / (1.0 + refraction_index);
+        r0 = r0 * r0;
+        r0 + (1.0 - r0) * (1.0 - cosine).powi(5)
+    }
 }
\ No newline at end of file