From ca4a3854380ba01b3c316fc13b5dcb310fba1eca Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Fri, 14 Sep 2018 11:33:19 -0700
Subject: [PATCH] Stub cube impl.

---
 rtiow/src/bin/tracer.rs | 44 +++++++++++++++++++++++++++++++++
 rtiow/src/cube.rs       | 55 +++++++++++++++++++++++++++++++++++++++++
 rtiow/src/lib.rs        |  1 +
 3 files changed, 100 insertions(+)
 create mode 100644 rtiow/src/cube.rs

diff --git a/rtiow/src/bin/tracer.rs b/rtiow/src/bin/tracer.rs
index a7f2224..6eefec5 100644
--- a/rtiow/src/bin/tracer.rs
+++ b/rtiow/src/bin/tracer.rs
@@ -12,6 +12,7 @@ use rand::Rng;
 use structopt::StructOpt;
 
 use rtiow::camera::Camera;
+use rtiow::cube::Cube;
 use rtiow::hitable::Hit;
 use rtiow::hitable_list::HitableList;
 use rtiow::material::Dielectric;
@@ -172,10 +173,51 @@ fn build_scene_tutorial(opt: &Opt) -> Scene {
     }
 }
 
+fn build_scene_cube(opt: &Opt) -> Scene {
+    let lookfrom = Vec3::new(3., 3., 2.);
+    let lookat = Vec3::new(0., 0., 0.);
+    let dist_to_focus = (lookfrom - lookat).length();
+    let aperture = 0.1;
+    let camera = Camera::new(
+        lookfrom,
+        lookat,
+        Vec3::new(0., 1., 0.),
+        45.,
+        opt.width as f32 / opt.height as f32,
+        aperture,
+        dist_to_focus,
+    );
+    let world = HitableList::new(vec![
+        Box::new(Sphere::new(
+            Vec3::new(0., 0., -1.),
+            0.5,
+            Box::new(Lambertian::new(Vec3::new(0.1, 0.2, 0.5))),
+        )),
+        Box::new(Cube::new(
+            Vec3::new(0., 0., 0.),
+            0.5,
+            Box::new(Lambertian::new(Vec3::new(0.5, 0.2, 0.1))),
+        )),
+        Box::new(Sphere::new(
+            Vec3::new(0., -100.5, -1.),
+            100.,
+            Box::new(Lambertian::new(Vec3::new(0.8, 0.8, 0.8))),
+        )),
+    ]);
+    Scene {
+        camera,
+        world,
+        subsamples: opt.subsamples,
+        width: opt.width,
+        height: opt.height,
+    }
+}
+
 #[derive(Debug)]
 pub enum Model {
     Book,
     Tutorial,
+    Cube,
 }
 
 #[derive(Debug)]
@@ -193,6 +235,7 @@ impl str::FromStr for Model {
         match s {
             "book" => Ok(Model::Book),
             "tutorial" => Ok(Model::Tutorial),
+            "cube" => Ok(Model::Cube),
             _ => Err(ModelParseError(s.to_owned())),
         }
     }
@@ -223,6 +266,7 @@ fn main() -> Result<(), std::io::Error> {
     let opt = Opt::from_args();
     let scene = match opt.model {
         Model::Book => build_scene_book(&opt),
+        Model::Cube => build_scene_cube(&opt),
         Model::Tutorial => build_scene_tutorial(&opt),
     };
     let res = render(scene, &opt.output);
diff --git a/rtiow/src/cube.rs b/rtiow/src/cube.rs
new file mode 100644
index 0000000..b127e46
--- /dev/null
+++ b/rtiow/src/cube.rs
@@ -0,0 +1,55 @@
+use hitable::Hit;
+use hitable::HitRecord;
+use material::Material;
+use ray::Ray;
+use vec3::dot;
+use vec3::Vec3;
+
+pub struct Cube {
+    center: Vec3,
+    length: f32,
+    material: Box<Material>,
+}
+
+impl Cube {
+    pub fn new(center: Vec3, length: f32, material: Box<Material>) -> Cube {
+        Cube {
+            center,
+            length,
+            material,
+        }
+    }
+}
+
+impl Hit for Cube {
+    fn hit(&self, r: Ray, t_min: f32, t_max: f32) -> Option<HitRecord> {
+        let oc = r.origin() - self.center;
+        let a = dot(r.direction(), r.direction());
+        let b = dot(oc, r.direction());
+        let c = dot(oc, oc) - self.length * self.length;
+        let discriminant = b * b - a * c;
+        if discriminant > 0. {
+            let temp = (-b - (b * b - a * c).sqrt()) / a;
+            if temp < t_max && temp > t_min {
+                let point = r.point_at_parameter(temp);
+                return Some(HitRecord {
+                    t: temp,
+                    p: point,
+                    normal: (point - self.center) / self.length,
+                    material: &*self.material,
+                });
+            }
+            let temp = (-b + (b * b - a * c).sqrt()) / a;
+            if temp < t_max && temp > t_min {
+                let point = r.point_at_parameter(temp);
+                return Some(HitRecord {
+                    t: temp,
+                    p: point,
+                    normal: (point - self.center) / self.length,
+                    material: &*self.material,
+                });
+            }
+        }
+        None
+    }
+}
diff --git a/rtiow/src/lib.rs b/rtiow/src/lib.rs
index 58db044..d3a55ac 100644
--- a/rtiow/src/lib.rs
+++ b/rtiow/src/lib.rs
@@ -1,4 +1,5 @@
 pub mod camera;
+pub mod cube;
 pub mod hitable;
 pub mod hitable_list;
 pub mod material;