1 files changed, 13 insertions, 14 deletions

diff --git a/src/world/shapes/sphere.rs b/src/world/shapes/sphere.rs
index fc2cfe2..36c9d13 100644
--- a/src/world/shapes/sphere.rs
+++ b/src/world/shapes/sphere.rs
@@ -3,35 +3,30 @@
 //! Spheres are relatively easy to calculate intersections between
 use crate::{Float, NEAR_ZERO};
 use crate::core::{Ray, Vector3f, Bound3f};
-use crate::world::{Hittable, DynHittable, Intersection};
+use crate::world::{Hittable, DynHittable, Intersection, Instancable};
 
 pub struct Sphere {
     radius: Float,
-    center: Vector3f,
 }
 
 impl Sphere {
-    pub fn new(radius: Float, center: Vector3f) -> Sphere {
+    pub fn new(radius: Float) -> Sphere {
         Sphere {
             radius,
-            center,
         }
     }
 
     fn norm_at(&self, point: &Vector3f) -> Vector3f {
-        let mut v = *point - self.center;
-        v /= self.radius;
-        v
+        *point / self.radius
     }
 }
 
 impl Hittable for Sphere {
     // Implementation from ray tracing in a weekend
     fn intersect(&self, ray: &Ray) -> Option<Intersection> {
-        let oc = ray.origin - self.center;
         let a = ray.direction.len_squared();
-        let half_b = oc.dot(&ray.direction);
-        let c = oc.len_squared() - self.radius * self.radius;
+        let half_b = ray.origin.dot(&ray.direction);
+        let c = ray.origin.len_squared() - self.radius * self.radius;
         let disc = half_b*half_b - a*c;
 
         if disc < 0.0 {
@@ -67,18 +62,21 @@ impl Hittable for Sphere {
     /// use rendering::core::Vector3f;
     /// use rendering::world::{Hittable, shapes::Sphere};
     ///
-    /// let sph = Sphere::new(1.0, Vector3f::new(0.0));
+    /// let sph = Sphere::new(1.0);
     /// let b = sph.bounding_box();
     ///
     /// assert!(b.min.x == -1.0 && b.min.y == -1.0 && b.min.z == -1.0);
     /// assert!(b.max.x == 1.0 && b.max.y == 1.0 && b.max.z == 1.0);
+    /// ```
     fn bounding_box(&self) -> Bound3f {
         let offset = Vector3f::new(self.radius);
 
-        Bound3f::new(self.center - offset, self.center + offset)
+        Bound3f::new(-offset, offset)
     }
 }
 
+impl Instancable for Sphere {}
+
 impl Into<DynHittable> for Sphere {
     fn into(self) -> DynHittable {
         DynHittable::new(Box::new(self))
@@ -91,7 +89,7 @@ mod tests {
 
     #[test]
     fn sphere_intersect() {
-        let sph = Sphere::new(2.0, Vector3f::new_xyz(2.0, 3.0, 4.0));
+        let sph = Sphere::new(2.0);
 
         let ray = Ray {
             origin: Vector3f::new_xyz(1.0, 0.0, 0.0),
@@ -99,6 +97,7 @@ mod tests {
         };
 
         let dist = sph.intersect(&ray).unwrap();
-        assert!((dist.t - 3.28).abs() < 0.01);
+        println!("Yay {}", dist.t);
+        assert!((dist.t - 1.732).abs() < 0.01);
     }
 }