4 files changed, 149 insertions, 0 deletions
diff --git a/src/world/mod.rs b/src/world/mod.rs
new file mode 100644
index 0000000..ef239db
--- /dev/null
+++ b/src/world/mod.rs
@@ -0,0 +1,23 @@
+//! Manages world objects, and implements intersection
+pub mod shapes;
+
+mod scene;
+pub use scene::*;
+
+use std::rc::Rc;
+use crate::core::Hittable;
+use crate::material::Material;
+
+pub struct Object {
+    pub shape: Box<dyn Hittable>,
+    pub mat: Rc<dyn Material>,
+}
+
+impl Object {
+    pub fn new(mat: Rc<dyn Material>, shape: Box<dyn Hittable>) -> Self {
+        Object {
+            mat,
+            shape,
+        }
+    }
+}
diff --git a/src/world/scene.rs b/src/world/scene.rs
new file mode 100644
index 0000000..444e915
--- /dev/null
+++ b/src/world/scene.rs
@@ -0,0 +1,52 @@
+use crate::core::{Ray, Intersection};
+use crate::material::Material;
+
+use super::Object;
+
+pub struct Scene {
+    objs: Vec<Object>,
+}
+
+pub struct SceneIntersect<'a> {
+    pub mat: &'a dyn Material,
+    pub i: Intersection,
+}
+
+impl Scene {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn add_object(&mut self, obj: Object) {
+        self.objs.push(obj);
+    }
+
+    pub fn add_objects(&mut self, objs: Vec<Object>) {
+        for obj in objs {
+            self.add_object(obj);
+        }
+    }
+
+    pub fn intersect(&self, ray: &Ray) -> Option<SceneIntersect> {
+        let mut min: Option<SceneIntersect> = None;
+
+        for obj in self.objs.iter() {
+            if let Some(i) = obj.shape.intersect(&ray) {
+                match min {
+                    Some(ref si) if si.i.t < i.t => (),
+                    _ => min = Some(SceneIntersect {i, mat: obj.mat.as_ref() }),
+                }
+            }
+        }
+
+        min
+    }
+}
+
+impl Default for Scene {
+    fn default() -> Self {
+        Self {
+            objs: Vec::new(),
+        }
+    }
+}
diff --git a/src/world/shapes/mod.rs b/src/world/shapes/mod.rs
new file mode 100644
index 0000000..d7583ad
--- /dev/null
+++ b/src/world/shapes/mod.rs
@@ -0,0 +1,4 @@
+mod sphere;
+
+pub use sphere::Sphere;
+
diff --git a/src/world/shapes/sphere.rs b/src/world/shapes/sphere.rs
new file mode 100644
index 0000000..8e0816b
--- /dev/null
+++ b/src/world/shapes/sphere.rs
@@ -0,0 +1,70 @@
+//! Implements sphere
+//!
+//! Spheres are relatively easy to calculate intersections between
+use crate::Float;
+use crate::core::{Ray, Vector3f, Hittable, Intersection};
+
+pub struct Sphere {
+    radius: Float,
+    center: Vector3f,
+}
+
+impl Sphere {
+    pub fn new(radius: Float, center: Vector3f) -> Sphere {
+        Sphere {
+            radius,
+            center,
+        }
+    }
+
+    fn norm_at(&self, point: &Vector3f) -> Vector3f {
+        let mut v = *point - self.center;
+        v /= self.radius;
+        v
+    }
+}
+
+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 disc = half_b*half_b - a*c;
+
+        if disc < 0.0 {
+            None
+        } else {
+            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,
+                t: distance,
+            })
+        }
+
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn sphere_intersect() {
+        let sph = Sphere::new(2.0, Vector3f::new_xyz(2.0, 3.0, 4.0));
+
+        let ray = Ray {
+            origin: Vector3f::new_xyz(1.0, 0.0, 0.0),
+            direction: Vector3f::new_xyz(0.0, 1.0, 1.5).norm(),
+        };
+
+        let dist = sph.intersect(&ray).unwrap();
+        assert!((dist.t - 3.28).abs() < 0.01);
+    }
+}