Added Dielectrics, Implemented Neg for Vec3

.gitignore

@@ -1,2 +1,3 @@
 target/
 *.ppm
+*.png

src/demos/dielectric_material.rs

@@ -0,0 +1,103 @@
+use {
+    crate::{
+        demos::{Chunk, Demo},
+        types::{
+            material::{Dielectric, Lambertian, Metal},
+            Hitable, HitableList, Ray, Sphere, Vec3,
+        },
+        Camera,
+    },
+    rand::Rng,
+};
+
+pub struct DielectricMaterial;
+
+impl Demo for DielectricMaterial {
+    fn name(&self) -> &'static str {
+        "dielectric-material"
+    }
+
+    fn render_chunk(&self, chunk: &mut Chunk, samples: u8) {
+        let x = chunk.x;
+        let y = chunk.y;
+        let nx = chunk.nx;
+        let ny = chunk.ny;
+        let start_x = chunk.start_x;
+        let start_y = chunk.start_y;
+        let buffer = &mut chunk.buffer;
+
+        let world = HitableList {
+            list: vec![
+                Box::new(Sphere::with_material(
+                    Vec3::new(0.0, 0.0, -1.0),
+                    0.5,
+                    Box::new(Lambertian::new(Vec3::new(0.1, 0.2, 0.5))),
+                )),
+                Box::new(Sphere::with_material(
+                    Vec3::new(0.0, -100.5, -1.0),
+                    100.0,
+                    Box::new(Lambertian::new(Vec3::new(0.8, 0.8, 0.0))),
+                )),
+                Box::new(Sphere::with_material(
+                    Vec3::new(1.0, 0.0, -1.0),
+                    0.5,
+                    Box::new(Metal::new(Vec3::new(0.8, 0.6, 0.2))),
+                )),
+                Box::new(Sphere::with_material(
+                    Vec3::new(-1.0, 0.0, -1.0),
+                    0.5,
+                    Box::new(Dielectric::new(1.5)),
+                )),
+                Box::new(Sphere::with_material(
+                    Vec3::new(-1.0, 0.0, -1.0),
+                    -0.45,
+                    Box::new(Dielectric::new(1.5)),
+                )),
+            ],
+        };
+
+        let camera: Camera = Default::default();
+        let mut rng = rand::thread_rng();
+        let mut offset = 0;
+
+        for j in start_y..start_y + ny {
+            for i in start_x..start_x + nx {
+                let mut color = Vec3::new(0.0, 0.0, 0.0);
+                for _s in 0..samples {
+                    let u = (i as f64 + rng.gen::<f64>()) / x as f64;
+                    let v = (j as f64 + rng.gen::<f64>()) / y as f64;
+
+                    let ray = camera.get_ray(u, v);
+                    color += calc_color(ray, &world, 0);
+                }
+
+                color /= samples as f64;
+
+                // gamma 2 corrected
+                buffer[offset] = (255.99 * color.r().sqrt()) as u8;
+                buffer[offset + 1] = (255.99 * color.g().sqrt()) as u8;
+                buffer[offset + 2] = (255.99 * color.b().sqrt()) as u8;
+                offset += 4;
+            }
+        }
+    }
+}
+
+fn calc_color(ray: Ray, world: &HitableList, depth: u32) -> Vec3 {
+    if let Some(hit_rec) = world.hit(&ray, 0.001, std::f64::MAX) {
+        if depth >= 50 {
+            Vec3::new(0.0, 0.0, 0.0)
+        } else {
+            let material = hit_rec.material.as_ref();
+            if let (attenuation, Some(scattered_ray)) = material.unwrap().scatter(&ray, &hit_rec) {
+                calc_color(scattered_ray, &world, depth + 1) * attenuation
+            } else {
+                Vec3::new(0.0, 0.0, 0.0)
+            }
+        }
+    } else {
+        let unit_direction = ray.direction().unit_vector();
+        let t = 0.5 * (unit_direction.y() + 1.0);
+        Vec3::new(1.0, 1.0, 1.0) * (1.0 - t) + Vec3::new(0.5, 0.7, 1.0) * t
+    }
+}

src/demos/diffuse_materials.rs

@@ -67,7 +67,7 @@ fn calc_color(ray: Ray, world: &HitableList, rng: &mut rand::rngs::ThreadRng) ->
     // To combat this problem, We set a bias
     // More information here, https://www.opengl-tutorial.org/intermediate-tutorials/tutorial-16-shadow-mapping/#shadow-acne
     if let Some(hit_rec) = world.hit(&ray, 0.001, std::f64::MAX) {
-        let target = hit_rec.p + hit_rec.normal + random_point_in_unit_space(rng);
+        let target = hit_rec.p + hit_rec.normal + random_point_in_unit_sphere(rng);
         calc_color(Ray::new(hit_rec.p, target - hit_rec.p), &world, rng) * 0.5
     } else {
         let unit_direction = ray.direction().unit_vector();
@@ -76,7 +76,7 @@ fn calc_color(ray: Ray, world: &HitableList, rng: &mut rand::rngs::ThreadRng) ->
     }
 }
 
-fn random_point_in_unit_space(rng: &mut rand::rngs::ThreadRng) -> Vec3 {
+fn random_point_in_unit_sphere(rng: &mut rand::rngs::ThreadRng) -> Vec3 {
     let mut point = Vec3::new(rng.gen::<f64>(), rng.gen::<f64>(), rng.gen::<f64>()) * 2.0
         - Vec3::new(1.0, 1.0, 1.0);
     while point.sq_len() >= 1.0 {

src/demos/materials.rs

@@ -1,7 +1,10 @@
 use {
     crate::{
         demos::{Chunk, Demo},
-        types::{material, Hitable, HitableList, Ray, Sphere, Vec3},
+        types::{
+            material::{Lambertian, Metal},
+            Hitable, HitableList, Ray, Sphere, Vec3,
+        },
         Camera,
     },
     rand::Rng,
@@ -11,7 +14,7 @@ pub struct Materials;
 
 impl Demo for Materials {
     fn name(&self) -> &'static str {
-        "Metal Material"
+        "metal-material"
     }
 
     fn render_chunk(&self, chunk: &mut Chunk, samples: u8) {
@@ -28,22 +31,22 @@ impl Demo for Materials {
                 Box::new(Sphere::with_material(
                     Vec3::new(0.0, 0.0, -1.0),
                     0.5,
-                    Box::new(material::Lambertian::new(Vec3::new(0.8, 0.3, 0.3))),
+                    Box::new(Lambertian::new(Vec3::new(0.8, 0.3, 0.3))),
                 )),
                 Box::new(Sphere::with_material(
                     Vec3::new(0.0, -100.5, -1.0),
                     100.0,
-                    Box::new(material::Lambertian::new(Vec3::new(0.8, 0.8, 0.0))),
+                    Box::new(Lambertian::new(Vec3::new(0.8, 0.8, 0.0))),
                 )),
                 Box::new(Sphere::with_material(
                     Vec3::new(1.0, 0.0, -1.0),
                     0.5,
-                    Box::new(material::Metal::new(Vec3::new(0.8, 0.6, 0.2))),
+                    Box::new(Metal::with_fuzz(Vec3::new(0.8, 0.6, 0.2), 0.3)),
                 )),
                 Box::new(Sphere::with_material(
                     Vec3::new(-1.0, 0.0, -1.0),
                     0.5,
-                    Box::new(material::Metal::new(Vec3::new(0.8, 0.8, 0.8))),
+                    Box::new(Metal::with_fuzz(Vec3::new(0.8, 0.8, 0.8), 0.5)),
                 )),
             ],
         };

src/demos/mod.rs

@@ -1,3 +1,4 @@
+mod dielectric_material;
 mod diffuse_materials;
 mod hitable_sphere;
 mod linear_gradient_rectangle;
@@ -7,6 +8,7 @@ mod simple_rectangle;
 mod simple_sphere;
 mod surface_normal_sphere;
 
+pub use dielectric_material::DielectricMaterial;
 pub use diffuse_materials::DiffuseMaterials;
 pub use hitable_sphere::HitableSphere;
 pub use linear_gradient_rectangle::LinearGradientRectangle;

src/main.rs

@@ -78,6 +78,7 @@ fn main() -> Result<(), String> {
                         Some(Keycode::Num6) => active_demo = Box::new(demos::SimpleAntialiasing),
                         Some(Keycode::Num7) => active_demo = Box::new(demos::DiffuseMaterials),
                         Some(Keycode::Num8) => active_demo = Box::new(demos::Materials),
+                        Some(Keycode::Num9) => active_demo = Box::new(demos::DielectricMaterial),
                         None => unreachable!(),
                         _ => (),
                     };

src/types/hitable.rs

@@ -1,9 +1,23 @@
 use crate::types::{Material, Ray, Vec3};
 
 pub struct HitRecord<'a> {
+    ///  Rays are represented by A + t * B
+    ///  where A is the source point and B destination point
+    ///  by adjusting t we can move forward/back on the ray
+    ///
+    ///  t is the point at which a ray intersected another object.
+    ///  As in, If we put this value of t in A + t * B equation, We'll get the exact
+    ///  point at which a ray intersects some other object
     pub t: f64,
+    /// Ray object otherwise is represented by the Source/Destination points
+    /// p is what we get when we perform the operation, A + t * B
+    /// i.e. A vector from Ray source to the point t
     pub p: Vec3,
+
+    /// unit outward facing normal
     pub normal: Vec3,
+
+    /// material if any of the surface
     pub material: Option<&'a Box<dyn Material>>,
 }
 

src/types/material.rs

@@ -2,6 +2,7 @@ use {
     crate::types::{HitRecord, Ray, Vec3},
     rand::Rng,
 };
+
 pub trait Material {
     fn scatter(&self, ray: &Ray, hit_rec: &HitRecord) -> (Vec3, Option<Ray>);
 }
@@ -10,46 +11,45 @@ pub struct Lambertian {
     albedo: Vec3,
 }
 
-impl Material for Lambertian {
-    fn scatter(&self, _ray: &Ray, hit_rec: &HitRecord) -> (Vec3, Option<Ray>) {
-        let mut rng = rand::thread_rng();
-        let target = hit_rec.p + hit_rec.normal + random_point_in_unit_space(&mut rng);
-        let scattered_ray = Ray::new(hit_rec.p, target - hit_rec.p);
-
-        (self.albedo, Some(scattered_ray))
-    }
-}
-
 impl Lambertian {
     pub fn new(a: Vec3) -> Self {
         Self { albedo: a }
     }
 }
 
-fn random_point_in_unit_space(rng: &mut rand::rngs::ThreadRng) -> Vec3 {
+impl Material for Lambertian {
-    let mut point = Vec3::new(rng.gen::<f64>(), rng.gen::<f64>(), rng.gen::<f64>()) * 2.0
+    fn scatter(&self, _ray: &Ray, hit_rec: &HitRecord) -> (Vec3, Option<Ray>) {
-        - Vec3::new(1.0, 1.0, 1.0);
+        let mut rng = rand::thread_rng();
-    while point.sq_len() >= 1.0 {
+        let target = hit_rec.p + hit_rec.normal + random_point_in_unit_sphere(&mut rng);
-        point = Vec3::new(rng.gen::<f64>(), rng.gen::<f64>(), rng.gen::<f64>()) * 2.0
+        let scattered_ray = Ray::new(hit_rec.p, target - hit_rec.p);
-            - Vec3::new(1.0, 1.0, 1.0);
+
+        (self.albedo, Some(scattered_ray))
     }
-    point
 }
 
 pub struct Metal {
     albedo: Vec3,
+    fuzz: f64,
 }
 
 impl Metal {
     pub fn new(albedo: Vec3) -> Self {
-        Self { albedo }
+        Self { albedo, fuzz: 0.0 }
+    }
+    pub fn with_fuzz(albedo: Vec3, fuzz: f64) -> Self {
+        Self { albedo, fuzz }
     }
 }
 
 impl Material for Metal {
     fn scatter(&self, ray_in: &Ray, hit_rec: &HitRecord) -> (Vec3, Option<Ray>) {
+        let mut rng = rand::thread_rng();
+
         let reflected_ray = reflect(ray_in.direction().unit_vector(), hit_rec.normal);
-        let scattered_ray = Ray::new(hit_rec.p, reflected_ray);
+        let scattered_ray = Ray::new(
+            hit_rec.p,
+            reflected_ray + random_point_in_unit_sphere(&mut rng) * self.fuzz,
+        );
 
         if scattered_ray.direction().dot(&hit_rec.normal) > 0.0 {
             (self.albedo, Some(scattered_ray))
@@ -59,6 +59,82 @@ impl Material for Metal {
     }
 }
 
+pub struct Dielectric {
+    reflection_index: f64,
+}
+
+impl Dielectric {
+    pub fn new(reflection_index: f64) -> Self {
+        Self { reflection_index }
+    }
+}
+
+impl Material for Dielectric {
+    fn scatter(&self, ray_in: &Ray, hit_rec: &HitRecord) -> (Vec3, Option<Ray>) {
+        let reflected_ray = reflect(ray_in.direction(), hit_rec.normal);
+        // Glass absorbs nothing! So, Attenuation is always going to be 1.0 for this
+        let attenuation = Vec3::new(1.0, 1.0, 1.0);
+        let mut rng = rand::thread_rng();
+
+        let (outward_normal, ni_over_nt, cosine) = if ray_in.direction().dot(&hit_rec.normal) > 0.0
+        {
+            (
+                -hit_rec.normal,
+                self.reflection_index,
+                (ray_in.direction().dot(&hit_rec.normal) * self.reflection_index)
+                    / ray_in.direction().length(),
+            )
+        } else {
+            (
+                hit_rec.normal,
+                1.0 / self.reflection_index,
+                (-ray_in.direction().dot(&hit_rec.normal)) / ray_in.direction().length(),
+            )
+        };
+
+        if let Some(refracted_ray) = refract(ray_in.direction(), outward_normal, ni_over_nt) {
+            let reflect_prob = schlick(cosine, self.reflection_index);
+
+            if rng.gen::<f64>() < reflect_prob {
+                (attenuation, Some(Ray::new(hit_rec.p, reflected_ray)))
+            } else {
+                (attenuation, Some(Ray::new(hit_rec.p, refracted_ray)))
+            }
+        } else {
+            (attenuation, Some(Ray::new(hit_rec.p, reflected_ray)))
+        }
+    }
+}
+
+// Polynomial approximation to figure out reflectivity as the angle changes
+fn schlick(cosine: f64, reflection_index: f64) -> f64 {
+    let mut r0 = (1.0 - reflection_index) / (1.0 + reflection_index);
+    r0 = r0 * r0;
+    r0 + (1.0 - r0) * (1.0 - cosine).powf(5.0)
+}
+
 fn reflect(incident: Vec3, normal: Vec3) -> Vec3 {
     incident - normal * incident.dot(&normal) * 2.0
 }
+
+// Snell's Law
+fn refract(incident: Vec3, normal: Vec3, ni_over_nt: f64) -> Option<Vec3> {
+    let uv = incident.unit_vector();
+    let dt = uv.dot(&normal);
+    let discriminant = 1.0 - ni_over_nt * ni_over_nt * (1.0 - dt * dt);
+    if discriminant > 0.0 {
+        Some((uv - normal * dt) * ni_over_nt - normal * discriminant.sqrt())
+    } else {
+        None
+    }
+}
+
+fn random_point_in_unit_sphere(rng: &mut rand::rngs::ThreadRng) -> Vec3 {
+    let mut point = Vec3::new(rng.gen::<f64>(), rng.gen::<f64>(), rng.gen::<f64>()) * 2.0
+        - Vec3::new(1.0, 1.0, 1.0);
+    while point.sq_len() >= 1.0 {
+        point = Vec3::new(rng.gen::<f64>(), rng.gen::<f64>(), rng.gen::<f64>()) * 2.0
+            - Vec3::new(1.0, 1.0, 1.0);
+    }
+    point
+}

src/types/sphere.rs

@@ -1,4 +1,5 @@
 use crate::types::{HitRecord, Hitable, Material, Ray, Vec3};
+
 pub struct Sphere {
     center: Vec3,
     radius: f64,
@@ -36,9 +37,10 @@ impl Hitable for Sphere {
         // Check this for detailed proof
         // https://vchizhov.github.io/resources/ray%20tracing/ray%20tracing%20tutorial%20series%20vchizhov/ray_casting/part1/intersecting_a_sphere.md.html#appendix
         let discriminant = b * b - a * c;
+        let discriminant_root = discriminant.sqrt();
 
         if discriminant > 0.0 {
-            let root = (-b - discriminant.sqrt()) / a;
+            let root = (-b - discriminant_root) / a;
             if root < t_max && root > t_min {
                 let p = ray.point_at_parameter(root);
                 return Some(HitRecord {
@@ -49,7 +51,7 @@ impl Hitable for Sphere {
                 });
             }
 
-            let root = (-b + discriminant.sqrt()) / a;
+            let root = (-b + discriminant_root) / a;
             if root < t_max && root > t_min {
                 let p = ray.point_at_parameter(root);
 

src/types/vec3.rs

@@ -1,6 +1,6 @@
 use std::{
     fmt::{Display, Formatter, Result as FmtResult},
-    ops::{Add, AddAssign, Div, DivAssign, Index, IndexMut, Mul, MulAssign, Sub, SubAssign},
+    ops::{Add, AddAssign, Div, DivAssign, Index, IndexMut, Mul, MulAssign, Neg, Sub, SubAssign},
 };
 
 #[derive(Copy, Clone)]
@@ -107,6 +107,14 @@ impl SubAssign for Vec3 {
     }
 }
 
+impl Neg for Vec3 {
+    type Output = Vec3;
+
+    fn neg(self) -> Vec3 {
+        Vec3([-self[0], -self[1], -self[2]])
+    }
+}
+
 impl MulAssign<Vec3> for Vec3 {
     fn mul_assign(&mut self, o: Vec3) {
         self[0] *= o[0];