4 files changed, 57 insertions, 37 deletions

diff --git a/src/scene/mod.rs b/src/scene/mod.rs
index 7c77412..f8c1e09 100644
--- a/src/scene/mod.rs
+++ b/src/scene/mod.rs
@@ -5,3 +5,28 @@ pub mod shapes;
 
 mod scene;
 pub use scene::*;
+
+use crate::core::{Ray, Vector3f};
+use crate::Float;
+
+/// Returns the context of a intersection
+pub struct Intersection {
+    /// Normal vector at intersection
+    pub n: Vector3f,
+    pub p: Vector3f,
+}
+
+impl Intersection {
+    pub fn norm_against_ray(&self, r: &Ray) -> Vector3f {
+        if self.n.dot(&r.direction) < 0.0 {
+            self.n
+        } else {
+            -self.n
+        }
+    }
+}
+
+/// Defines a common trait for objects in the scene
+pub trait Hittable {
+    fn intersect(&self, ray: &Ray) -> Option<Intersection>;
+}
diff --git a/src/scene/scene.rs b/src/scene/scene.rs
index 33a7613..367003e 100644
--- a/src/scene/scene.rs
+++ b/src/scene/scene.rs
@@ -1,14 +1,10 @@
-use super::shapes::Shape;
-use crate::Float;
+use super::{Intersection, Hittable};
 use crate::core::Ray;
 
-pub struct Scene {
-    shps: Vec<Box<dyn Shape>>,
-}
+type Shape = Box<dyn Hittable>;
 
-pub struct Intersection<'a> {
-    pub shp: &'a dyn Shape,
-    pub t: Float,
+pub struct Scene {
+    shps: Vec<Shape>,
 }
 
 impl Scene {
@@ -18,17 +14,20 @@ impl Scene {
         }
     }
 
-    pub fn add_shape(&mut self, shp: Box<dyn Shape>) {
+    pub fn add_shape(&mut self, shp: Shape) {
         self.shps.push(shp);
     }
 
+    pub fn add_shapes(&mut self, shps: Vec<Shape>) {
+        for shp in shps {
+            self.add_shape(shp);
+        }
+    }
+
     pub fn intersect(&self, ray: &Ray) -> Option<Intersection> {
         for shp in self.shps.iter() {
-            if let Some(t) = shp.intersect(&ray) {
-                return Some(Intersection {
-                    shp: shp.as_ref(),
-                    t,
-                })
+            if let Some(i) = shp.intersect(&ray) {
+                return Some(i)
             }
         }
 
diff --git a/src/scene/shapes/mod.rs b/src/scene/shapes/mod.rs
index 9b6bdfd..d7583ad 100644
--- a/src/scene/shapes/mod.rs
+++ b/src/scene/shapes/mod.rs
@@ -2,15 +2,3 @@ mod sphere;
 
 pub use sphere::Sphere;
 
-use crate::core::{Vector3f, Ray};
-use crate::Float;
-
-pub trait Shape {
-    fn intersect(&self, ray: &Ray) -> Option<Float>;
-
-    /// Calculates the normal at point
-    ///
-    /// Point is assumed to be on the circle.
-    /// The resulting vector is assumed to be normalized.
-    fn norm_at(&self, point: &Vector3f) -> Vector3f;
-}
diff --git a/src/scene/shapes/sphere.rs b/src/scene/shapes/sphere.rs
index da7f321..acca2b7 100644
--- a/src/scene/shapes/sphere.rs
+++ b/src/scene/shapes/sphere.rs
@@ -3,7 +3,7 @@
 //! Spheres are relatively easy to calculate intersections between
 use crate::Float;
 use crate::core::{Ray, Vector3f};
-use super::Shape;
+use crate::scene::{Hittable, Intersection};
 
 pub struct Sphere {
     radius: Float,
@@ -17,11 +17,17 @@ impl Sphere {
             center,
         }
     }
+
+    fn norm_at(&self, point: &Vector3f) -> Vector3f {
+        let mut v = *point - self.center;
+        v /= self.radius;
+        v
+    }
 }
 
-impl Shape for Sphere {
+impl Hittable for Sphere {
     // Implementation from ray tracing in a weekend
-    fn intersect(&self, ray: &Ray) -> Option<Float> {
+    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);
@@ -29,18 +35,20 @@ impl Shape for Sphere {
         let disc = half_b*half_b - a*c;
 
         if disc < 0.0 {
-            None
+            return None
         } else {
-            Some( (-half_b - disc.sqrt()) / a)
+            let distance = (-half_b - disc.sqrt()) / a;
+            if distance < 0.0 {
+                return None
+            }
+            let w = ray.at(distance);
+            Some(Intersection {
+                n: self.norm_at(&w),
+                p: w,
+            })
         }
 
     }
-
-    fn norm_at(&self, point: &Vector3f) -> Vector3f {
-        let mut v = *point - self.center;
-        v /= self.radius;
-        v
-    }
 }
 
 #[cfg(test)]