1 files changed, 83 insertions, 0 deletions
diff --git a/src/hittable/instance/rotate_x.rs b/src/hittable/instance/rotate_x.rs
new file mode 100644
index 0000000..4ebc04d
--- /dev/null
+++ b/src/hittable/instance/rotate_x.rs
@@ -0,0 +1,83 @@
+use std::sync::Arc;
+
+use crate::{hittable::{HitRecord, Hittable, AABB}, ray::Ray, util::degrees_to_radians, vec3::{Point3, Vec3}};
+
+pub struct RotateX {
+    hittable: Arc<dyn Hittable>,
+    sin_theta: f64,
+    cos_theta: f64,
+    aabb: Option<AABB>,
+}
+
+impl RotateX {
+    pub fn new(hittable: Arc<dyn Hittable>, angle: f64) -> Self {
+        let radians = degrees_to_radians(angle);
+        let sin_theta = radians.sin();
+        let cos_theta = radians.cos();
+        match hittable.bounding_box(0.0, 1.0) { // TODO: passing in 0.0 and 1.0 for time seems suspicious.
+            None => Self { hittable, sin_theta, cos_theta, aabb: None },
+            Some(aabb) => {
+                let mut min = Point3 { x: f64::INFINITY, y: f64::INFINITY, z: f64::INFINITY };
+                let mut max = Point3 { x: -f64::INFINITY, y: -f64::INFINITY, z: -f64::INFINITY };
+                for i in 0..2 {
+                    for j in 0..2 {
+                        for k in 0..2 {
+                            let x = i as f64 * aabb.maximum.x + (1.0 - i as f64) * aabb.minimum.x;
+                            let y = j as f64 * aabb.maximum.y + (1.0 - j as f64) * aabb.minimum.y;
+                            let z = k as f64 * aabb.maximum.z + (1.0 - k as f64) * aabb.minimum.z;
+                            let new_y = cos_theta * y + sin_theta * y;
+                            let new_z = -sin_theta * y + cos_theta * z;
+
+                            let tester = Vec3 { y: new_y, x, z: new_z };
+                            for c in 0..3 {
+                                *min.get_mut(c).unwrap() = min.get(c).unwrap().min(*tester.get(c).unwrap());
+                                *max.get_mut(c).unwrap() = max.get(c).unwrap().max(*tester.get(c).unwrap());
+                            }
+                        }
+                    }
+                }
+                let aabb = AABB { minimum: min, maximum: max };
+
+                Self {
+                    hittable,
+                    sin_theta,
+                    cos_theta,
+                    aabb: Some(aabb),
+                }
+            }
+        }
+    }
+}
+
+impl Hittable for RotateX {
+    fn hit(&self, ray: &Ray, t_min: f64, t_max: f64) -> Option<HitRecord> {
+        let mut origin = ray.origin.clone();
+        let mut direction = ray.direction.clone();
+
+        origin.y = self.cos_theta * ray.origin.y - self.sin_theta * ray.origin.z;
+        origin.z = self.sin_theta * ray.origin.y + self.cos_theta * ray.origin.z;
+        
+        direction.y = self.cos_theta * ray.direction.y - self.sin_theta * ray.direction.z;
+        direction.z = self.sin_theta * ray.direction.y + self.cos_theta * ray.direction.z;
+
+        let rotated_ray = Ray { origin, direction, time: ray.time };
+        let mut hit_record = self.hittable.hit(&rotated_ray, t_min, t_max)?;
+
+        let mut p = hit_record.p.clone();
+        let mut normal = hit_record.normal.clone();
+
+        p.y = self.cos_theta * hit_record.p.y+ self.sin_theta * hit_record.p.z;
+        p.z = -self.sin_theta * hit_record.p.y + self.cos_theta * hit_record.p.z;
+
+        normal.y = self.cos_theta * hit_record.normal.y + self.sin_theta * hit_record.normal.z;
+        normal.z = -self.sin_theta * hit_record.normal.y + self.cos_theta * hit_record.normal.z;
+
+        hit_record.p = p;
+        hit_record.set_face_normal(&ray, &normal);
+        Some(hit_record)
+    }
+
+    fn bounding_box(&self, _: f64, _: f64) -> Option<AABB> {
+        self.aabb.clone()
+    }
+}