Implement kd-tree.

Add simple test scene.
Failed attempt to make BVH faster.
Failed attempt to implement SAH w/ BVH.
Failed attempt to make AABB::hit faster.

rtiow/src/aabb.rs

@@ -35,6 +35,30 @@ impl AABB {
         AABB { bounds: [min, max] }
     }
 
+    pub fn volume(&self) -> f32 {
+        (self.min().x - self.max().x).abs()
+            * (self.min().y - self.max().y).abs()
+            * (self.min().z - self.max().z).abs()
+    }
+
+    pub fn longest_axis(&self) -> usize {
+        let xd = (self.min().x - self.max().x).abs();
+        let yd = (self.min().y - self.max().y).abs();
+        let zd = (self.min().z - self.max().z).abs();
+
+        if xd >= yd && xd >= zd {
+            return 0;
+        }
+        if yd >= xd && yd >= zd {
+            return 1;
+        }
+        return 2;
+    }
+
+    pub fn mid_point(&self) -> Vec3 {
+        self.bounds[0] + (self.bounds[1] - self.bounds[0]) / 2.
+    }
+
     pub fn min(&self) -> Vec3 {
         self.bounds[0]
     }
@@ -64,7 +88,7 @@ impl AABB {
         true
     }
 
-    pub fn hit(&self, r: Ray, t0: f32, t1: f32) -> bool {
+    pub fn hit_precompute(&self, r: Ray, t0: f32, t1: f32) -> bool {
         let mut t_min = (self.bounds[r.sign[0]].x - r.origin.x) * r.inv_direction.x;
         let mut t_max = (self.bounds[1 - r.sign[0]].x - r.origin.x) * r.inv_direction.x;
         let t_y_min = (self.bounds[r.sign[0]].y - r.origin.y) * r.inv_direction.y;
@@ -95,7 +119,7 @@ impl AABB {
         t_min < t1 && t_max > t0
     }
 
-    pub fn hit_original(&self, r: Ray, t_min: f32, t_max: f32) -> bool {
+    pub fn hit(&self, r: Ray, t_min: f32, t_max: f32) -> bool {
         let mut t_min = t_min;
         let mut t_max = t_max;
         for axis in 0..3 {

rtiow/src/bin/tracer.rs

@@ -13,9 +13,7 @@ use cpuprofiler::PROFILER;
 use structopt::StructOpt;
 
 use rtiow::renderer::render;
-use rtiow::renderer::Model;
 use rtiow::renderer::Opt;
-use rtiow::scenes;
 
 fn main() -> Result<(), std::io::Error> {
     stderrlog::new()
@@ -25,14 +23,7 @@ fn main() -> Result<(), std::io::Error> {
         .unwrap();
     let start = Instant::now();
     let opt = Opt::from_args();
-    let scene = match opt.model {
-        Model::Book => scenes::book::new(false, &opt),
-        Model::Bench => scenes::bench::new(&opt),
-        Model::BookBVH => scenes::book::new(true, &opt),
-        Model::Cube => scenes::cube::new(&opt),
-        Model::Tutorial => scenes::tutorial::new(&opt),
-        Model::BVH => scenes::bvh::new(&opt),
-    };
+    let scene = opt.model.scene(&opt);
     fs::create_dir_all(&opt.output)?;
     let pprof_path = "pprof.profile";
     if opt.pprof {

rtiow/src/bvh.rs

@@ -68,16 +68,112 @@ fn box_z_compare(ah: &Box<Hit>, bh: &Box<Hit>) -> std::cmp::Ordering {
     }
 }
 
+// Return the first element from the vector, which should be the only element.
+// TODO(wathiede): we really want a .first_into() (.first() doesn't work because it
+// returns a reference.)
+fn vec_first_into<T>(v: Vec<T>) -> T {
+    if v.len() != 1 {
+        panic!(format!(
+            "vec_first_into called for vector length != 1, length {}",
+            v.len()
+        ));
+    }
+    for i in v.into_iter() {
+        return i;
+    }
+    panic!("Unreachable");
+}
+
+fn vec_split_into<T>(v: Vec<T>, offset: usize) -> (Vec<T>, Vec<T>) {
+    let mut left_half = Vec::new();
+    let mut right_half = Vec::new();
+    v.into_iter().enumerate().for_each(|(i, h)| {
+        if i < offset {
+            left_half.push(h);
+        } else {
+            right_half.push(h);
+        }
+    });
+    (left_half, right_half)
+}
+
 impl BVHNode {
-    fn new(l: Vec<Box<Hit>>, t_min: f32, t_max: f32) -> BVHNode {
-        if l.len() == 1 {
-            // Return the first element from the vector, which should be the only element.
-            // TODO(wathiede): we really want a .first_into() (.first() doesn't work because it
-            // returns a reference.)
-            for h in l.into_iter() {
-                return BVHNode::Leaf(h);
+    fn new_sah(l: Vec<Box<Hit>>, t_min: f32, t_max: f32) -> BVHNode {
+        eprintln!("l.len() {}", l.len());
+        let mut l: Vec<Box<Hit>> = l.into_iter().collect();
+        let n = l.len();
+        let main_box =
+            l[1..]
+                .iter()
+                .fold(l[0].bounding_box(t_min, t_max).unwrap(), |acc, h| {
+                    match h.bounding_box(t_min, t_max) {
+                        Some(new_box) => surrounding_box(&new_box, &acc),
+                        None => panic!("hit without bounding box"),
+                    }
+                });
+
+        let axis = main_box.longest_axis();
+        match axis {
+            0 => l.sort_by(box_x_compare),
+            1 => l.sort_by(box_y_compare),
+            2 => l.sort_by(box_z_compare),
+            val @ _ => panic!("unknown axis {}", val),
+        };
+        let boxes: Vec<_> = l
+            .iter()
+            .map(|hit| hit.bounding_box(t_min, t_max).unwrap())
+            .collect();
+
+        let mut left_area = Vec::with_capacity(n);
+        let mut left_box = boxes[0].clone();
+        for i in 1..n - 1 {
+            left_box = surrounding_box(&left_box, &boxes[i]);
+            left_area[i] = left_box.volume();
+        }
+
+        let mut right_area = Vec::with_capacity(n);
+        right_area[n - 1] = boxes[n - 1].volume();
+        let mut right_box = boxes[n - 1].clone();
+        for i in (0..n - 2).rev() {
+            right_box = surrounding_box(&right_box, &boxes[i]);
+            right_area[i] = right_box.volume();
+        }
+
+        let mut min_sah = std::f32::MAX;
+        let mut min_sah_idx = 0;
+        for i in 0..n - 1 {
+            let sah = i as f32 * left_area[i] + (n - i - 1) as f32 * right_area[i + 1];
+            if sah < min_sah {
+                min_sah_idx = i;
+                min_sah = sah;
             }
-            panic!("Unreachable");
+        }
+
+        let left: Box<BVHNode>;
+        let right: Box<BVHNode>;
+        if min_sah_idx == 0 {
+            let (l, r) = vec_split_into(l, 1);
+            left = Box::new(BVHNode::Leaf(vec_first_into(l)));
+            right = Box::new(BVHNode::new_sah(r, t_min, t_max));
+        } else if min_sah_idx == n - 2 {
+            let (l, r) = vec_split_into(l, min_sah_idx + 1);
+            left = Box::new(BVHNode::new_sah(l, t_min, t_max));
+            right = Box::new(BVHNode::Leaf(vec_first_into(r)));
+        } else {
+            let (l, r) = vec_split_into(l, min_sah_idx + 1);
+            left = Box::new(BVHNode::new_sah(l, t_min, t_max));
+            right = Box::new(BVHNode::new_sah(r, t_min, t_max));
+        }
+
+        BVHNode::Branch {
+            left,
+            right,
+            bbox: Some(main_box),
+        }
+    }
+    fn new_dumb(l: Vec<Box<Hit>>, t_min: f32, t_max: f32) -> BVHNode {
+        if l.len() == 1 {
+            return BVHNode::Leaf(vec_first_into(l));
         } else {
             let mut l: Vec<Box<Hit>> = l.into_iter().collect();
             let mut rng = rand::thread_rng();
@@ -88,18 +184,10 @@ impl BVHNode {
                 val @ _ => panic!("unknown axis {}", val),
             }
 
-            let mut left_half = Vec::new();
-            let mut right_half = Vec::new();
-            let half_idx = l.len() / 2;
-            l.into_iter().enumerate().for_each(|(i, h)| {
-                if i < half_idx {
-                    left_half.push(h);
-                } else {
-                    right_half.push(h);
-                }
-            });
-            let left = Box::new(BVHNode::new(left_half, t_min, t_max));
-            let right = Box::new(BVHNode::new(right_half, t_min, t_max));
+            let half = l.len() / 2;
+            let (left_half, right_half) = vec_split_into(l, half);
+            let left = Box::new(BVHNode::new_dumb(left_half, t_min, t_max));
+            let right = Box::new(BVHNode::new_dumb(right_half, t_min, t_max));
             let bbox = BVHNode::surrounding_box(left.as_ref(), right.as_ref(), t_min, t_max);
             return BVHNode::Branch { left, right, bbox };
         }
@@ -129,6 +217,7 @@ impl Hit for BVHNode {
     fn hit(&self, r: Ray, t_min: f32, t_max: f32) -> Option<HitRecord> {
         match self {
             BVHNode::Leaf(ref hit) => hit.hit(r, t_min, t_max),
+            // TODO(wathiede): call bbox.hit() before recursing down both paths of tree.
             BVHNode::Branch {
                 ref left,
                 ref right,
@@ -163,7 +252,7 @@ impl BVH {
         let count = l.len();
         let start = Instant::now();
         let bvh = BVH {
-            root: BVHNode::new(l, t_min, t_max),
+            root: BVHNode::new_sah(l, t_min, t_max),
         };
         let runtime = start.elapsed();
         info!(

rtiow/src/cube.rs

@@ -25,6 +25,8 @@ impl Cube {
 
 impl Hit for Cube {
     fn hit(&self, r: Ray, t_min: f32, t_max: f32) -> Option<HitRecord> {
+        info!("Cube info");
+        eprintln!("Cube eprintln");
         // See if it hit the positive X wall first.
         let oc = r.origin - self.center;
         let a = dot(r.direction, r.direction);

rtiow/src/kdtree.rs

@@ -0,0 +1,188 @@
+use std::fmt;
+
+use aabb::surrounding_box;
+use aabb::AABB;
+use hitable::Hit;
+use hitable::HitRecord;
+use ray::Ray;
+
+pub enum KDTree {
+    Leaf(Box<Hit>),
+    Branch {
+        left: Box<KDTree>,
+        right: Box<KDTree>,
+        bbox: Option<AABB>,
+    },
+}
+
+// Return the first element from the vector, which should be the only element.
+// TODO(wathiede): we really want a .first_into() (.first() doesn't work because it
+// returns a reference.)
+fn vec_first_into<T>(v: Vec<T>) -> T {
+    if v.len() != 1 {
+        panic!(format!(
+            "vec_first_into called for vector length != 1, length {}",
+            v.len()
+        ));
+    }
+    for i in v.into_iter() {
+        return i;
+    }
+    panic!("Unreachable");
+}
+
+fn vec_split_into<T>(v: Vec<T>, offset: usize) -> (Vec<T>, Vec<T>) {
+    let mut left_half = Vec::new();
+    let mut right_half = Vec::new();
+    v.into_iter().enumerate().for_each(|(i, h)| {
+        if i < offset {
+            left_half.push(h);
+        } else {
+            right_half.push(h);
+        }
+    });
+    (left_half, right_half)
+}
+
+impl KDTree {
+    pub fn new(l: Vec<Box<Hit>>, t_min: f32, t_max: f32) -> KDTree {
+        if l.len() == 0 {
+            panic!("Attempt to build k-d tree with no Hit objects");
+        }
+
+        if l.len() == 1 {
+            return KDTree::Leaf(vec_first_into(l));
+        }
+
+        if l.len() == 2 {
+            let (left_vec, right_vec) = vec_split_into(l, 1);
+            let left = vec_first_into(left_vec);
+            let right = vec_first_into(right_vec);
+            let bbox = surrounding_box(
+                &left.bounding_box(t_min, t_max).unwrap(),
+                &right.bounding_box(t_min, t_max).unwrap(),
+            );
+            return KDTree::Branch {
+                left: Box::new(KDTree::Leaf(left)),
+                right: Box::new(KDTree::Leaf(right)),
+                bbox: Some(bbox),
+            };
+        }
+        let bbox = l[0].bounding_box(t_min, t_max).unwrap();
+        let mut mid_point = bbox.mid_point();
+        let bbox = l[1..].iter().fold(bbox, |acc, h| {
+            let new_bbox = &h.bounding_box(t_min, t_max).unwrap();
+            mid_point = mid_point + new_bbox.mid_point();
+            surrounding_box(&acc, new_bbox)
+        });
+        mid_point = mid_point / l.len() as f32;
+        let axis = bbox.longest_axis();
+        let mut left_half = Vec::new();
+        let mut right_half = Vec::new();
+        match axis {
+            0 => l.into_iter().for_each(|h| {
+                if h.bounding_box(t_min, t_max).unwrap().mid_point().x < mid_point.x {
+                    left_half.push(h);
+                } else {
+                    right_half.push(h);
+                }
+            }),
+            1 => l.into_iter().for_each(|h| {
+                if h.bounding_box(t_min, t_max).unwrap().mid_point().y < mid_point.y {
+                    left_half.push(h);
+                } else {
+                    right_half.push(h);
+                }
+            }),
+            2 => l.into_iter().for_each(|h| {
+                if h.bounding_box(t_min, t_max).unwrap().mid_point().z < mid_point.z {
+                    left_half.push(h);
+                } else {
+                    right_half.push(h);
+                }
+            }),
+            _ => panic!("Unreachable"),
+        };
+        KDTree::Branch {
+            left: Box::new(KDTree::new(left_half, t_min, t_max)),
+            right: Box::new(KDTree::new(right_half, t_min, t_max)),
+            bbox: Some(bbox),
+        }
+    }
+
+    fn volume(&self) -> f32 {
+        let bbox = self.bounding_box(0., 0.).unwrap();
+        (bbox.min().x - bbox.max().x).abs()
+            * (bbox.min().y - bbox.max().y).abs()
+            * (bbox.min().z - bbox.max().z).abs()
+    }
+}
+
+fn print_tree(f: &mut fmt::Formatter, depth: usize, kdt: &KDTree) -> fmt::Result {
+    let vol = kdt.volume();
+    write!(f, "{:8.2}{}", vol, " ".repeat(depth * 2))?;
+    match kdt {
+        KDTree::Leaf(ref hit) => write!(
+            f,
+            "Leaf: {}\n",
+            hit.bounding_box(0., 0.)
+                .map_or("NO BBOX".to_owned(), |bb| bb.to_string())
+        )?,
+        KDTree::Branch { bbox, .. } => write!(
+            f,
+            "Branch: {}\n",
+            // TODO(wathiede): removing this .clone() results in a complaint about moving out
+            // of a borrow.
+            bbox.clone()
+                .map_or("NO BBOX".to_owned(), |bb| bb.to_string())
+        )?,
+    }
+    if let KDTree::Branch { left, right, .. } = kdt {
+        print_tree(f, depth + 1, left)?;
+        print_tree(f, depth + 1, right)?;
+    }
+    Ok(())
+}
+
+impl fmt::Display for KDTree {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "kd-tree\n")?;
+        print_tree(f, 1, &self)
+    }
+}
+impl Hit for KDTree {
+    fn hit(&self, r: Ray, t_min: f32, t_max: f32) -> Option<HitRecord> {
+        match self.bounding_box(t_min, t_max) {
+            Some(bbox) => if !bbox.hit(r, t_min, t_max) {
+                return None;
+            },
+            None => {
+                info!("KDTree::hit no bbox: {:?}", r);
+                return None;
+            }
+        }
+        match self {
+            KDTree::Leaf(ref hit) => hit.hit(r, t_min, t_max),
+            KDTree::Branch { left, right, bbox } => match bbox {
+                None => None,
+                Some(_bbox) => match (left.hit(r, t_min, t_max), right.hit(r, t_min, t_max)) {
+                    (Some(hit_left), Some(hit_right)) => if hit_left.t < hit_right.t {
+                        return Some(hit_left);
+                    } else {
+                        return Some(hit_right);
+                    },
+                    (Some(hit_left), None) => Some(hit_left),
+                    (None, Some(hit_right)) => Some(hit_right),
+                    (None, None) => None,
+                },
+            },
+        }
+    }
+
+    fn bounding_box(&self, t_min: f32, t_max: f32) -> Option<AABB> {
+        match self {
+            KDTree::Leaf(ref hit) => hit.bounding_box(t_min, t_max),
+            KDTree::Branch { bbox, .. } => bbox.clone(),
+        }
+    }
+}

rtiow/src/lib.rs

@@ -4,6 +4,7 @@ pub mod camera;
 pub mod cube;
 pub mod hitable;
 pub mod hitable_list;
+pub mod kdtree;
 pub mod material;
 pub mod moving_sphere;
 pub mod ray;

rtiow/src/ray.rs

@@ -1,6 +1,6 @@
 use vec3::Vec3;
 
-#[derive(Copy, Clone, Default)]
+#[derive(Copy, Clone, Debug, Default)]
 pub struct Ray {
     pub origin: Vec3,
     pub direction: Vec3,

rtiow/src/renderer.rs

@@ -16,16 +16,30 @@ use rand::Rng;
 use camera::Camera;
 use hitable::Hit;
 use ray::Ray;
+use scenes;
 use vec3::Vec3;
 
 #[derive(Debug)]
 pub enum Model {
     Bench,
     Book,
-    BookBVH,
     Tutorial,
     Cube,
     BVH,
+    Test,
+}
+
+impl Model {
+    pub fn scene(&self, opt: &Opt) -> Scene {
+        match self {
+            Model::Book => scenes::book::new(&opt),
+            Model::Bench => scenes::bench::new(&opt),
+            Model::Cube => scenes::cube::new(&opt),
+            Model::Tutorial => scenes::tutorial::new(&opt),
+            Model::BVH => scenes::bvh::new(&opt),
+            Model::Test => scenes::test::new(&opt),
+        }
+    }
 }
 
 #[derive(Debug)]
@@ -43,10 +57,10 @@ impl str::FromStr for Model {
         match s {
             "bench" => Ok(Model::Bench),
             "book" => Ok(Model::Book),
-            "book_bvh" => Ok(Model::BookBVH),
             "tutorial" => Ok(Model::Tutorial),
             "cube" => Ok(Model::Cube),
             "bvh" => Ok(Model::BVH),
+            "test" => Ok(Model::Test),
             _ => Err(ModelParseError(s.to_owned())),
         }
     }
@@ -56,18 +70,21 @@ impl str::FromStr for Model {
 #[structopt(name = "tracer", about = "An experimental ray tracer.")]
 pub struct Opt {
     /// Image width
-    #[structopt(short = "w", long = "width", default_value = "128")]
+    #[structopt(short = "w", long = "width", default_value = "1024")]
     pub width: usize,
     /// Image height
-    #[structopt(short = "h", long = "height", default_value = "128")]
+    #[structopt(short = "h", long = "height", default_value = "1024")]
     pub height: usize,
     /// Sub-samples per pixel
     #[structopt(short = "s", long = "subsample", default_value = "1")]
     pub subsamples: usize,
-    #[structopt(long = "model", default_value = "bench")]
+    #[structopt(long = "model", default_value = "test")]
     pub model: Model,
     #[structopt(long = "pprof")]
     pub pprof: bool,
+    /// Use acceleration data structure, may be BVH or kd-tree depending on scene.
+    #[structopt(long = "use_accel")]
+    pub use_accel: bool,
 
     /// Output directory
     #[structopt(parse(from_os_str), default_value = "/tmp/tracer")]

rtiow/src/scenes/bench.rs

@@ -1,10 +1,10 @@
 use rand;
 use rand::Rng;
 
-use bvh::BVH;
 use camera::Camera;
 use hitable::Hit;
 use hitable_list::HitableList;
+use kdtree::KDTree;
 use material::Lambertian;
 use renderer::Opt;
 use renderer::Scene;
@@ -12,7 +12,7 @@ use sphere::Sphere;
 use vec3::Vec3;
 
 pub fn new(opt: &Opt) -> Scene {
-    let lookfrom = Vec3::new(0.01, 20., 0.);
+    let lookfrom = Vec3::new(20., 20., 20.);
     let lookat = Vec3::new(0., 0., 0.);
     let dist_to_focus = (lookfrom - lookat).length();
     let aperture = 0.1;
@@ -31,7 +31,7 @@ pub fn new(opt: &Opt) -> Scene {
     );
     let mut rng = rand::thread_rng();
     let mut grid: Vec<Box<Hit>> = Vec::new();
-    let len = 30;
+    let len = 100;
     for x in 0..len {
         for z in 0..len {
             let r = rng.gen_range::<f32>(0., 1.);
@@ -45,12 +45,12 @@ pub fn new(opt: &Opt) -> Scene {
             )));
         }
     }
-    let use_bvh = false;
+    let use_kdtree = true;
     let world: Box<Hit>;
-    if use_bvh {
-        let bvh = BVH::new(grid, time_min, time_max);
-        trace!(target: "bvh", "World {}", bvh);
-        world = Box::new(bvh);
+    if use_kdtree {
+        let kdtree = KDTree::new(grid, time_min, time_max);
+        //trace!(target: "k-d tree", "World {}", kdtree);
+        world = Box::new(kdtree);
     } else {
         world = Box::new(HitableList::new(grid));
     }

rtiow/src/scenes/book.rs

@@ -5,6 +5,7 @@ use bvh::BVH;
 use camera::Camera;
 use hitable::Hit;
 use hitable_list::HitableList;
+use kdtree::KDTree;
 use material::Dielectric;
 use material::Lambertian;
 use material::Metal;
@@ -13,7 +14,7 @@ use renderer::Scene;
 use sphere::Sphere;
 use vec3::Vec3;
 
-pub fn new(bvh: bool, opt: &Opt) -> Scene {
+pub fn new(opt: &Opt) -> Scene {
     let lookfrom = Vec3::new(13., 2., 3.);
     let lookat = Vec3::new(0., 0., 0.);
     let dist_to_focus = 10.;
@@ -31,14 +32,16 @@ pub fn new(bvh: bool, opt: &Opt) -> Scene {
         time_min,
         time_max,
     );
-    let world: Box<Hit>;
-    if bvh {
-        let b = BVH::new(random_scene(), time_min, time_max);
-        trace!(target: "bvh", "World {}", b);
-        world = Box::new(b);
+    let ground_color = if opt.use_accel {
+        Vec3::new(1.0, 0.4, 0.4)
     } else {
-        world = Box::new(HitableList::new(random_scene()));
-    }
+        Vec3::new(0.4, 1.0, 0.4)
+    };
+    let world: Box<Hit> = if opt.use_accel {
+        Box::new(KDTree::new(random_scene(ground_color), time_min, time_max))
+    } else {
+        Box::new(HitableList::new(random_scene(ground_color)))
+    };
     Scene {
         camera,
         world,
@@ -48,12 +51,12 @@ pub fn new(bvh: bool, opt: &Opt) -> Scene {
     }
 }
 
-fn random_scene() -> Vec<Box<Hit>> {
+fn random_scene(background_color: Vec3) -> Vec<Box<Hit>> {
     let mut rng = rand::thread_rng();
     let mut objects: Vec<Box<Hit>> = vec![Box::new(Sphere::new(
         Vec3::new(0., -1000., 0.),
         1000.,
-        Box::new(Lambertian::new(Vec3::new(0.5, 0.5, 0.5))),
+        Box::new(Lambertian::new(background_color)),
     ))];
     let mut random = || rng.gen_range::<f32>(0., 1.);
 

rtiow/src/scenes/mod.rs

@@ -2,4 +2,5 @@ pub mod bench;
 pub mod book;
 pub mod bvh;
 pub mod cube;
+pub mod test;
 pub mod tutorial;

rtiow/src/scenes/test.rs

@@ -0,0 +1,80 @@
+use std::f32::consts::PI;
+
+use rand;
+use rand::Rng;
+
+use camera::Camera;
+use hitable::Hit;
+use hitable_list::HitableList;
+use kdtree::KDTree;
+use material::Lambertian;
+use material::Metal;
+use renderer::Opt;
+use renderer::Scene;
+use sphere::Sphere;
+use vec3::Vec3;
+
+pub fn new(opt: &Opt) -> Scene {
+    let lookfrom = Vec3::new(0.001, 0.001, 20.);
+    let lookat = Vec3::new(0., 0., 0.);
+    let dist_to_focus = (lookfrom - lookat).length();
+    let aperture = 0.1;
+    let time_min = 0.;
+    let time_max = 0.;
+    let camera = Camera::new(
+        lookfrom,
+        lookat,
+        Vec3::new(0., 1., 0.),
+        45.,
+        opt.width as f32 / opt.height as f32,
+        aperture,
+        dist_to_focus,
+        time_min,
+        time_max,
+    );
+    let mut objects: Vec<Box<Hit>> = vec![Box::new(Sphere::new(
+        Vec3::new(0., 0., 0.),
+        5.,
+        Box::new(Metal::new(Vec3::new(0.5, 0.5, 0.5), 0.)),
+    ))];
+    let num_spheres = 6;
+    let radius = 7.;
+    let mut rng = rand::thread_rng();
+    let mut random = || rng.gen_range::<f32>(0., 1.);
+    for i in 0..num_spheres {
+        let c1 = radius * ((2. * PI) * (i as f32 / num_spheres as f32)).sin();
+        let c2 = radius * ((2. * PI) * (i as f32 / num_spheres as f32)).cos();
+        let center = Vec3::new(0., c1, c2);
+        objects.push(Box::new(Sphere::new(
+            center,
+            0.5,
+            Box::new(Lambertian::new(Vec3::new(1., 0., 0.))),
+        )));
+        let center = Vec3::new(c1, 0., c2);
+        objects.push(Box::new(Sphere::new(
+            center,
+            0.5,
+            Box::new(Lambertian::new(Vec3::new(0., 1., 0.))),
+        )));
+        let center = Vec3::new(c1, c2, 0.);
+        objects.push(Box::new(Sphere::new(
+            center,
+            0.5,
+            Box::new(Lambertian::new(Vec3::new(0., 0., 1.))),
+        )));
+    }
+    let world: Box<Hit> = if opt.use_accel {
+        let kd = KDTree::new(objects, time_min, time_max);
+        //println!("{}", kd);
+        Box::new(kd)
+    } else {
+        Box::new(HitableList::new(objects))
+    };
+    Scene {
+        camera,
+        world,
+        subsamples: opt.subsamples,
+        width: opt.width,
+        height: opt.height,
+    }
+}

rtiow/src/scenes/tutorial.rs

@@ -1,6 +1,7 @@
 use camera::Camera;
 use hitable::Hit;
 use hitable_list::HitableList;
+use kdtree::KDTree;
 use material::Lambertian;
 use material::Metal;
 use moving_sphere::MovingSphere;
@@ -15,7 +16,7 @@ pub fn new(opt: &Opt) -> Scene {
     let dist_to_focus = (lookfrom - lookat).length();
     let aperture = 0.1;
     let time_min = 0.;
-    let time_max = 1.;
+    let time_max = 0.;
     let camera = Camera::new(
         lookfrom,
         lookat,
@@ -27,7 +28,14 @@ pub fn new(opt: &Opt) -> Scene {
         time_min,
         time_max,
     );
-    let world: Box<Hit> = Box::new(HitableList::new(vec![
+    let ground_color = if opt.use_accel {
+        Vec3::new(1.0, 0.4, 0.4)
+    } else {
+        Vec3::new(0.4, 1.0, 0.4)
+    };
+
+    let objects: Vec<Box<Hit>> = vec![
+        //let world: Box<Hit> = Box::new(HitableList::new(vec![
         Box::new(Sphere::new(
             Vec3::new(0., 0., -1.),
             0.5,
@@ -36,7 +44,7 @@ pub fn new(opt: &Opt) -> Scene {
         Box::new(Sphere::new(
             Vec3::new(0., -100.5, -1.),
             100.,
-            Box::new(Lambertian::new(Vec3::new(0.8, 0.8, 0.8))),
+            Box::new(Lambertian::new(ground_color)),
         )),
         Box::new(Sphere::new(
             Vec3::new(1., 0., -1.),
@@ -51,7 +59,12 @@ pub fn new(opt: &Opt) -> Scene {
             1.,
             Box::new(Lambertian::new(Vec3::new(0.2, 0.8, 0.2))),
         )),
-    ]));
+    ];
+    let world: Box<Hit> = if opt.use_accel {
+        Box::new(KDTree::new(objects, time_min, time_max))
+    } else {
+        Box::new(HitableList::new(objects))
+    };
     Scene {
         camera,
         world,