1 files changed, 61 insertions, 0 deletions
diff --git a/src/hittable/sphere.rs b/src/hittable/sphere.rs
new file mode 100644
index 0000000..783b788
--- /dev/null
+++ b/src/hittable/sphere.rs
@@ -0,0 +1,61 @@
+use std::sync::Arc;
+use std::f64::consts;
+
+use crate::{hittable::{HitRecord, Hittable, AABB}, material::Material, vec3::Vec3};
+use crate::ray::Ray;
+use crate::vec3::Point3;
+
+pub struct Sphere {
+    pub center: Point3,
+    pub radius: f64,
+    pub material: Arc<dyn Material>,
+}
+
+impl Sphere {
+    pub fn get_sphere_uv(p: &Point3, u: &mut f64, v: &mut f64) {
+        let theta = (-p.y).acos();
+        let phi = -p.z.atan2(p.x) + consts::PI;
+
+        *u = phi / (2.0 * consts::PI);
+        *v = theta / consts::PI;
+    }
+}
+
+impl Hittable for Sphere {
+    fn hit(&self, ray: &Ray, t_min: f64, t_max: f64) -> Option<HitRecord> {
+        let oc = &ray.origin - &self.center;
+        let a = ray.direction.length_squared();
+        let half_b = oc.dot(&ray.direction);
+        let c = oc.length_squared() - self.radius * self.radius;
+        let discriminant = half_b * half_b - a * c;
+        if discriminant < 0.0 {
+            return None;
+        }
+
+        let sqrtd = discriminant.sqrt();
+        // Find the nearest root that lies within acceptable range
+        let mut root = (-half_b - sqrtd) / a;
+        if root < t_min || t_max < root {
+            root = (-half_b + sqrtd) / a;
+            if root < t_min || t_max < root {
+                return None;
+            }
+        }
+
+        let mut hit_record = HitRecord::new();
+        hit_record.t = root;
+        hit_record.p = ray.at(hit_record.t);
+        let outward_normal = (&hit_record.p - &self.center) / self.radius;
+        hit_record.set_face_normal(ray, &outward_normal);
+        Self::get_sphere_uv(&outward_normal, &mut hit_record.u, &mut hit_record.v);
+        hit_record.material = Some(self.material.clone());
+        Some(hit_record)
+    }
+
+    fn bounding_box(&self, _: f64, _: f64) -> Option<AABB> {
+        Some(AABB {
+            minimum: &self.center - Vec3 { x: self.radius, y: self.radius, z: self.radius },
+            maximum: &self.center + Vec3 { x: self.radius, y: self.radius, z: self.radius },
+        })
+    }
+}