From 1af881f36e46a07a182693c5ab756bb006903242 Mon Sep 17 00:00:00 2001
From: Alan Jian <alanjian85@outlook.com>
Date: Wed, 17 Jul 2024 15:28:09 +0800
Subject: [PATCH] feat: add sphere to shapes

---
 src/core.rs   |  6 ++++++
 src/main.rs   | 21 ++++++---------------
 src/shapes.rs | 26 ++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 15 deletions(-)
 create mode 100644 src/shapes.rs

diff --git a/src/core.rs b/src/core.rs
index 4330378..ccd4684 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -14,3 +14,9 @@ impl Ray {
         self.orig + t * self.dir
     }
 }
+
+pub trait Intersect {
+    fn intersect(&self, _ray: &Ray) -> Option<f64> {
+        None
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 60f60f2..9015e23 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,31 +1,22 @@
 mod camera;
 mod cli;
 mod core;
+mod shapes;
 
 use camera::Camera;
 use clap::Parser;
 use cli::{Cli, Size};
-use core::Ray;
+use core::{Intersect, Ray};
 use image::{Rgb, RgbImage};
 use indicatif::ProgressBar;
 use nalgebra::{Point2, Point3, Vector3};
 use palette::{LinSrgb, Srgb};
-
-fn hit_sphere(center: Point3<f64>, radius: f64, ray: &Ray) -> Option<f64> {
-    let a = ray.dir.magnitude_squared();
-    let b = (-2.0 * ray.dir).dot(&(center - ray.orig));
-    let c = (center - ray.orig).magnitude_squared() - radius * radius;
-    let discriminant = b * b - 4.0 * a * c;
-    if discriminant < 0.0 {
-        return None;
-    }
-    Some((-b - discriminant.sqrt()) / (2.0 * a))
-}
+use shapes::Sphere;
 
 fn ray_color(ray: &Ray) -> LinSrgb<f64> {
-    let sphere_center = Point3::new(0.0, 0.0, -1.0);
-    if let Some(t) = hit_sphere(sphere_center, 0.5, ray) {
-        let normal = (ray.at(t) - sphere_center).normalize();
+    let sphere = Sphere::new(Point3::new(0.0, 0.0, -1.0), 0.5);
+    if let Some(t) = sphere.intersect(ray) {
+        let normal = (ray.at(t) - Point3::new(0.0, 0.0, -1.0)).normalize();
         let normal = 0.5 * (normal + Vector3::new(1.0, 1.0, 1.0));
         return LinSrgb::new(normal.x, normal.y, normal.z);
     }
diff --git a/src/shapes.rs b/src/shapes.rs
new file mode 100644
index 0000000..c5b0077
--- /dev/null
+++ b/src/shapes.rs
@@ -0,0 +1,26 @@
+use crate::{Intersect, Ray};
+use nalgebra::Point3;
+
+pub struct Sphere {
+    center: Point3<f64>,
+    radius: f64,
+}
+
+impl Sphere {
+    pub fn new(center: Point3<f64>, radius: f64) -> Self {
+        Self { center, radius }
+    }
+}
+
+impl Intersect for Sphere {
+    fn intersect(&self, ray: &Ray) -> Option<f64> {
+        let a = ray.dir.magnitude_squared();
+        let b = ray.dir.dot(&(self.center - ray.orig));
+        let c = (self.center - ray.orig).magnitude_squared() - self.radius * self.radius;
+        let discriminant = b * b - a * c;
+        if discriminant < 0.0 {
+            return None;
+        }
+        Some((b - discriminant.sqrt()) / a)
+    }
+}