From b6ec544b3ef98fdc4711fb44b8e97bf794ea7c3a Mon Sep 17 00:00:00 2001
From: Robert Garrett <robertgarrett404@gmail.com>
Date: Tue, 6 Jun 2023 19:14:17 -0500
Subject: [PATCH] Feat: Simulate depth-of-field

And with that, I'm on to the final render. Chapter 12 closed!
---
 src/camera.rs | 40 +++++++++++++++++++++++++++++-----------
 src/main.rs   | 21 ++++++++++++++-------
 src/vec3.rs   | 12 ++++++++++++
 3 files changed, 55 insertions(+), 18 deletions(-)

diff --git a/src/camera.rs b/src/camera.rs
index a7ed241..3a7bd1f 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -14,15 +14,28 @@ use crate::vec3::Vec3;
 use crate::ray::Ray;
 use crate::degrees_to_radians;
 
+use rand::rngs::SmallRng;
+use rand::distributions::Uniform;
+
 pub struct Camera {
-    pub origin: Vec3,
-    pub lower_left_corner: Vec3,
-    pub horizontal: Vec3,
-    pub vertical: Vec3,
+    origin: Vec3,
+    lower_left_corner: Vec3,
+    horizontal: Vec3,
+    vertical: Vec3,
+    u: Vec3, v: Vec3, w: Vec3,
+    lens_radius: f32,
 }
 
 impl Camera {
-    pub fn new(lookfrom: Vec3, lookat: Vec3, vup: Vec3, vfov: f32, aspect_ratio: f32) -> Camera {
+    pub fn new(
+        lookfrom: Vec3,
+        lookat: Vec3,
+        vup: Vec3,
+        vfov: f32,
+        aspect_ratio: f32,
+        aperture: f32,
+        focus_dist: f32
+    ) -> Camera {
         let theta = degrees_to_radians(vfov);
         let h = (theta / 2.0).tan();
         let vp_height = 2.0 * h;
@@ -33,25 +46,30 @@ impl Camera {
         let v = Vec3::cross(w, u);
 
         let orig = lookfrom;
-        let horiz = u * vp_width;
-        let verti = v * vp_height;
-        let lower_left_corner = orig - horiz / 2.0 - verti / 2.0 - w;
+        let horiz = u * vp_width * focus_dist;
+        let verti = v * vp_height * focus_dist;
+        let lower_left_corner = orig - horiz / 2.0 - verti / 2.0 - w * focus_dist;
 
         Camera{
             origin: orig,
             lower_left_corner,
             horizontal: horiz,
             vertical: verti,
+            u, v, w,
+            lens_radius: aperture / 2.0,
         }
     }
 
-    pub fn get_ray(&self, s: f32, t: f32) -> Ray {
+    pub fn get_ray(&self, s: f32, t: f32, srng: &mut SmallRng, distrib: Uniform<f32>) -> Ray {
+        let rd = Vec3::rand_in_unit_disk(srng, distrib) * self.lens_radius;
+        let offset = self.u * rd.x + self.v * rd.y;
+
         let dir = self.lower_left_corner
                 + self.horizontal * s
                 + self.vertical * t 
-                - self.origin;
+                - self.origin - offset;
         Ray{
-            orig: self.origin,
+            orig: self.origin + offset,
             dir,
         }
     }
diff --git a/src/main.rs b/src/main.rs
index 222162a..7ed9f3f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -25,8 +25,8 @@ fn main() {
     // image
     let aspect_ratio = 16.0 / 9.0;
     let image = (
-        400,
-        (400.0 / aspect_ratio) as i32
+        1920,
+        (1920.0 / aspect_ratio) as i32
     );
     let samples_per_pixel = 100;
     let max_depth = 50;
@@ -92,12 +92,19 @@ fn main() {
 
     // camera
 
+    let lookfrom = Vec3::new(3.0, 3.0, 2.0);
+    let lookat = Vec3::new(0.0, 0.0, -1.0);
+    let vup = Vec3::new(0.0, 1.0, 0.0);
+    let dist_to_focus = (lookfrom - lookat).length();
+    let aperture = 2.0;
     let cam = Camera::new(
-        Vec3::new(-2.0, 2.0, 1.0),
-        Vec3::new(0.0, 0.0, -1.0),
-        Vec3::new(0.0, 1.0, 0.0),
+        lookfrom,
+        lookat,
+        vup,
         20.0,
-        aspect_ratio
+        aspect_ratio,
+        aperture,
+        dist_to_focus
     );
 
     // render
@@ -112,7 +119,7 @@ fn main() {
             for _ in 0..samples_per_pixel {
                 let u = ((x as f32) + small_rng.sample(distrib_zero_one)) / ((image.0 - 1) as f32);
                 let v = ((y as f32) + small_rng.sample(distrib_zero_one)) / ((image.1 - 1) as f32);
-                let ray = cam.get_ray(u, v);
+                let ray = cam.get_ray(u, v, &mut small_rng, distrib_plusminus_one);
                 color+= ray_color(ray, &world, max_depth, &mut small_rng, distrib_plusminus_one);
             }
             println!("{}", color.print_ppm(samples_per_pixel));
diff --git a/src/vec3.rs b/src/vec3.rs
index 75078d8..e3b99ab 100644
--- a/src/vec3.rs
+++ b/src/vec3.rs
@@ -61,6 +61,18 @@ impl Vec3{
         }
     }
 
+    pub fn rand_in_unit_disk(srng: &mut SmallRng, distrib: Uniform<f32>) -> Vec3 {
+        loop {
+            let p = Vec3 {
+                x: srng.sample(distrib),
+                y: srng.sample(distrib),
+                z: 0.0,
+            };
+            if p.length_squared() >= 1.0 { continue; }
+            else { return p; }
+        }
+    }
+
     pub fn rand_unit_vector(srng: &mut SmallRng, distrib: Uniform<f32>) -> Vec3 {
         return Vec3::as_unit(Vec3::rand_in_unit_sphere(srng, distrib));
     }