From d4f0a226b59c62a5a72bc670501b692a20bec6b2 Mon Sep 17 00:00:00 2001
From: Jeremy5909 <jeremyherczeg@gmail.com>
Date: Wed, 1 May 2024 12:47:40 -0700
Subject: [PATCH] depth of field

---
 src/camera.rs | 23 ++++++++++++++++++-----
 src/main.rs   |  2 ++
 src/vec3.rs   | 10 ++++++++++
 3 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/src/camera.rs b/src/camera.rs
index e9b5dc5..0b29976 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -2,7 +2,7 @@ use std::{f64::INFINITY, io::stdout};
 
 use rand::{thread_rng, Rng};
 
-use crate::{color::{write_color, Color}, hittable::{HitRecord, Hittable}, interval::Interval, ray::Ray, vec3::{cross, unit_vector, Point3, Vec3}};
+use crate::{color::{write_color, Color}, hittable::{HitRecord, Hittable}, interval::Interval, ray::Ray, vec3::{cross, random_in_unit_disk, unit_vector, Point3, Vec3}};
 #[derive(Default)]
 pub struct Camera {
 	pub aspect_ratio: f64,
@@ -28,6 +28,11 @@ pub struct Camera {
 	u: Vec3,
 	v: Vec3,
 	w: Vec3,
+
+	pub defocus_angle: f64,
+	pub focus_dist: f64,
+	defocus_dist_u: Vec3,
+	defocus_dist_v: Vec3,
 }
 impl Camera {
 	pub fn new(aspect_ratio: f64, image_width: i32) -> Self {
@@ -38,6 +43,7 @@ impl Camera {
 			fov: 90.0,
 			look_at: Point3::new(0.0, 0.0, -1.0),
 			vup: Vec3::new(0.0, 1.0, 0.0),
+			focus_dist: 10.0,
 			..Default::default()}
 	}
 	pub fn render(&mut self, world: &dyn Hittable) {
@@ -64,10 +70,9 @@ impl Camera {
 		self.pixel_samples_scale = 1.0 / self.samples_per_pixel as f64;
 
 		self.center = self.look_from;
-		let focal_length = (self.look_from - self.look_at).length();
 		let theta = self.fov.to_radians();
 		let h = (theta/2.0).tan();		
-		let viewport_height = 2.0 * h * focal_length;
+		let viewport_height = 2.0 * h * self.focus_dist;
 		let viewport_width = viewport_height * (self.image_width as f64/self.image_height as f64);
 
 		self.w = unit_vector(&(self.look_from-self.look_at));
@@ -80,8 +85,12 @@ impl Camera {
 		self.pixel_delta_u = viewport_u / self.image_width as f64;
 		self.pixel_delta_v = viewport_v / self.image_height as f64;
 
-		let viewport_upper_left = self.center - (focal_length * self.w) - viewport_u/2.0 - viewport_v/2.0;
+		let viewport_upper_left = self.center - (self.focus_dist * self.w) - viewport_u/2.0 - viewport_v/2.0;
 		self.pixel00_loc = viewport_upper_left + 0.5 * (self.pixel_delta_u + self.pixel_delta_v);
+
+		let defocus_radius = self.focus_dist * (self.defocus_angle / 2.0).to_radians().tan();
+		self.defocus_dist_u = self.u * defocus_radius;
+		self.defocus_dist_v = self.v * defocus_radius;
 	}
 	fn ray_color(r: &Ray, depth: i32, world: &dyn Hittable) -> Color {
 		if depth <= 0 {
@@ -106,7 +115,7 @@ impl Camera {
 		let pixel_sample = self.pixel00_loc
 			+ ((i as f64 + offset.x()) * self.pixel_delta_u)
 			+ ((j as f64 + offset.y()) * self.pixel_delta_v);
-		let ray_origin = self.center;
+		let ray_origin = if self.defocus_angle <= 0.0 {self.center} else {self.defocus_disk_sample()};
 		let ray_direction = pixel_sample - ray_origin;
 		Ray::new(ray_origin, ray_direction)
 	}
@@ -114,4 +123,8 @@ impl Camera {
 		let mut rng = thread_rng();
 		Vec3::new(rng.gen_range(-0.5..0.5), rng.gen_range(-0.5..0.5), 0.0)
 	}
+	fn defocus_disk_sample(&self) -> Point3 {
+		let p = random_in_unit_disk();
+		self.center + (p[0] * self.defocus_dist_u) + (p[1] * self.defocus_dist_v)
+	}
 }
diff --git a/src/main.rs b/src/main.rs
index 53d9b8f..432c072 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -43,6 +43,8 @@ fn main() {
     cam.look_at = Point3::new(0.0, 0.0, -1.0);
     cam.vup = Vec3::new(0.0, 1.0, 0.0);
     cam.fov = 20.0;
+    cam.defocus_angle = 10.0;
+    cam.focus_dist = 3.4;
 
     cam.render(&world);
 }
diff --git a/src/vec3.rs b/src/vec3.rs
index 2e26f3b..f62655a 100644
--- a/src/vec3.rs
+++ b/src/vec3.rs
@@ -174,4 +174,14 @@ pub fn refract(uv: &Vec3, n: &Vec3, etai_over_etat: f64) -> Vec3 {
 	let r_out_perp = etai_over_etat * (*uv + cos_theta * *n);
 	let r_out_parallel = -(1.0 - r_out_perp.length_squared()).abs().sqrt() * *n;
 	r_out_parallel + r_out_perp
+}
+
+pub fn random_in_unit_disk() -> Vec3 {
+	let mut rng = thread_rng();
+	loop {
+		let p = Vec3::new(rng.gen_range(-1.0 .. 1.0), rng.gen_range(-1.0 .. 1.0), 0.0);
+		if p.length_squared() < 1.0 {
+			return p;
+		}
+	}
 }
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