Line renderer in terms of tile renderer

Done and done.

src/main.rs

@@ -1,41 +1,45 @@
 
 mod primitives;
-mod renderer;
 mod scene;
+mod renderer;
 
-use crate::primitives::Vec3;
+use crate::primitives::{
+    Vec2i,
+    Vec3,
+};
 use crate::scene::{
     Camera,
-    Hittable,
-    Material,
+    Scene
 };
-use crate::renderer::RenderCommand;
 
-use rand::{Rng, SeedableRng};
+use crate::renderer::{
+    Tile,
+    RenderProperties,
+};
+
+use rand::SeedableRng;
 use rand::rngs::SmallRng;
-use rand::distributions::Uniform;
 
-use std::thread;
 
 fn main() {
     // image
     let aspect_ratio = 3.0 / 2.0;
-    let image = (
-        1920,
-        (1920.0 / aspect_ratio) as i32
-    );
-    let samples_per_pixel: u32 = 10;
-    let max_depth = 50;
+    let image = Vec2i {
+        x: 400,
+        y: (400.0 / aspect_ratio) as i32
+    };
+
+    let render_config = RenderProperties {
+        samples: 10,
+        bounces: 50
+    };
 
     // random generator
     let mut small_rng = SmallRng::seed_from_u64(0);
 
-    // world
-    let world = random_scene(&mut small_rng);
-
-    // camera
-
-    let cam = Camera::new(
+    // Scene (now includes camera)
+    let scene = Scene {
+        camera: Camera::new(
             Vec3::new(13.0, 2.0, 3.0), // lookfrom
             Vec3::zero(), // lookat
             Vec3::new(0.0, 1.0, 0.0), // vup
@@ -43,174 +47,33 @@ fn main() {
             aspect_ratio, 
             0.1, // aperture
             10.0, // dist_to_focus
-    );
+        ),
+        world: Scene::random_world(&mut small_rng)
+    };
     
     // render
     // The render loop should now be a job submission mechanism
     // Iterate lines, submitting them as tasks to the thread.
-	println!("P3\n{} {}\n255", image.0, image.1);
-    let context = renderer::RenderContext {
-        camera: cam,
-        image,
-        max_depth,
-        samples_per_pixel,
-        world,
-    };
+	println!("P3\n{} {}\n255", image.x, image.y);
+    // TILE BASED RENDERER
+    // let tile = Tile::render_tile(
+    //     Rect { x: 0, y: 0, w: image.x, h: image.y },
+    //     image,
+    //     &scene,
+    //     &render_config,
+    //     &mut small_rng
+    // );
+    // for pixel in tile.pixels.iter().rev() {
+    //     println!("{}", pixel.print_ppm(render_config.samples));
+    // }
 
-    thread::scope(|s| {
-        let (mut dispatcher, scanline_receiver) = renderer::Dispatcher::new(&small_rng, 12);
-
-        s.spawn(move || {
-            for y in (0..image.1).rev() {
-                eprintln!("Submitting scanline: {}", y);
-                let job = RenderCommand::Line { line_num: y, context: context.clone() };
-                dispatcher.submit_job(job).unwrap();
-            }
-
-            dispatcher.submit_job(RenderCommand::Stop).unwrap();
-            // ... also I happen to know there are 4 threads.
-        });
-
-        /*
-         * Store received results in the segments buffer.
-         * Some will land before their previous segments and will need to be held
-         * until the next-to-write arrives.
-         *
-         * Elements are sorted in reverse order so that they can be popped from the
-         * Vec quickly.
-         *
-         * The queue is scanned every single time a new item is received. In the
-         * happy path where the received item is next-up, it'll be buffered, checked
-         * and then printed. In the case where it isn't, it'll get buffered and
-         * stick around for more loops. When the next-to-write finally lands, it
-         * means the n+1 element is up, now. If that element is already in the buffer
-         * we want to write it out. Hence the loop that scans the whole buffer each
-         * receive.
-         *
-         * TODO: There could be an up-front conditional that checks to see if the
-         * received item *is* the next-to-write and skip the buffering step.
-         * But I need to make the concept work at all, first.
-         */
-        let mut raster_segments = Vec::<renderer::RenderResult>::new();
-        let mut sl_output_index = image.1-1; // scanlines count down, start at image height.
-        while let Ok(scanline) = scanline_receiver.recv() {
-            eprintln!("Received scanline: {}", scanline.line_num);
-
-            raster_segments.push(scanline);
-            raster_segments.sort_by( |a, b| b.cmp(a) );
-
-            loop {
-                if raster_segments.len() == 0 { break; } // can this ever happen? Not while every
-                                                         // single element gets pushed to the
-                                                         // buffer first. With the happy path
-                                                         // short-circuit noted above, it could.
-
-                let last_ind = raster_segments.len() - 1;
-               if raster_segments[last_ind].line_num == sl_output_index{
-                    let scanline = raster_segments.pop().unwrap();
-                    print_scanline(scanline, samples_per_pixel);
-                    sl_output_index -= 1;
-                } else {
-                    break;
+    // LINE BASED RENDERER
+    for row in (0..image.y).rev() {
+        let tile = Tile::render_line(row, image, &scene, &render_config, &mut small_rng);
+        eprintln!("Printing scanline #{}", row);
+        for pixel in tile.pixels {
+            println!("{}", pixel.print_ppm(render_config.samples))
         }
     }
-        }
-        eprintln!("Size of raster_segments at finish: {}", raster_segments.len());
-    });
-    
-    
-    // TODO: Dispatcher shutdown mechanism. Right now, we might technically be leaking threads.
     eprintln!("Done!");
 }
-
-fn print_scanline(scanline: renderer::RenderResult, samples_per_pixel: u32){
-    eprintln!("Printing scanline num: {}", scanline.line_num);
-    for color in &scanline.line {
-        println!("{}", color.print_ppm(samples_per_pixel));
-    }
-}
-
-fn random_scene(srng: &mut SmallRng) -> Hittable {
-    let mat_ground = Material::Lambertian { albedo: Vec3::new(0.5, 0.5, 0.5) };
-    let mut world = Hittable::HittableList { hittables : Vec::<Hittable>::new() };
-    
-    world.push( Hittable::Sphere { center: Vec3::new(0.0, -1000.0, 0.0), radius: 1000.0, material: Some(mat_ground) });
-    
-    let distrib_zero_one = Uniform::new(0.0, 1.0);
-    for a in -11..11 {
-        for b in -11..11 {
-            let choose_mat = srng.sample(distrib_zero_one);
-            let center = Vec3 {
-                x: a as f32 + 0.9 * srng.sample(distrib_zero_one),
-                y: 0.2,
-                z: b as f32 + 0.9 * srng.sample(distrib_zero_one),
-            };
-            if (center - Vec3::new(4.0, 0.2, 0.0)).length() > 0.9 {
-
-                if choose_mat < 0.8 {
-                    // diffuse
-                    let albedo = Vec3::rand(srng, distrib_zero_one) * Vec3::rand(srng, distrib_zero_one);
-                    let sphere_material = Material::Lambertian { albedo };
-                    world.push(
-                        Hittable::Sphere {
-                            center,
-                            radius: 0.2,
-                            material: Some(sphere_material),
-                        }
-                    );
-                } else if choose_mat < 0.95 {
-                    // metal
-                    let distr_albedo = Uniform::new(0.5, 1.0);
-                    let distr_fuzz = Uniform::new(0.0, 0.5);
-
-                    let albedo = Vec3::rand(srng, distr_albedo);
-                    let fuzz = srng.sample(distr_fuzz);
-                    let material = Material::Metal { albedo, fuzz };
-                    world.push(
-                        Hittable::Sphere {
-                            center,
-                            radius: 0.2,
-                            material: Some(material),
-                        }
-                    );
-                } else {
-                    // glass
-                    let material = Material::Dielectric { index_refraction: 1.5 };
-                    world.push(
-                        Hittable::Sphere{
-                            center,
-                            radius: 0.2,
-                            material: Some(material),
-                        }
-                    );
-
-                };
-            }
-        }
-    }
-
-    let material1 = Material::Dielectric { index_refraction: 1.5 };
-    world.push( Hittable::Sphere{
-        center: Vec3::new(0.0, 1.0, 0.0),
-        radius: 1.0,
-        material: Some(material1)
-    });
-
-    let material2 = Material::Lambertian { albedo: Vec3::new(0.4, 0.2, 0.1) };
-    world.push( Hittable::Sphere {
-        center: Vec3::new(-4.0, 1.0, 0.0),
-        radius: 1.0,
-        material: Some(material2)
-    });
-
-    let material3 = Material::Metal { albedo: Vec3::new(0.7, 0.6, 0.5), fuzz: 0.0 };
-    world.push( Hittable::Sphere {
-        center: Vec3::new(4.0, 1.0, 0.0),
-        radius: 1.0,
-        material: Some(material3)
-    });
-
-    return world;
-}
-
-

src/primitives.rs

@@ -17,6 +17,96 @@ use rand::Rng;
 use rand::rngs::SmallRng;
 use rand::distributions::Uniform;
 
+pub type Vec2i = Vec2<i32>;
+pub type Vec2f = Vec2<f32>;
+
+#[derive (Clone, Copy, PartialEq, PartialOrd, Debug)]
+pub struct Vec2<T>{
+    pub x: T,
+    pub y: T,
+}
+
+
+impl Vec2<f32> {
+    pub fn zero() -> Vec2<f32> {
+        Vec2{ x: 0.0, y: 0.0 }
+    }
+
+    pub fn ones() -> Vec2<f32> {
+        Vec2{ x: 1.0, y: 1.0 }
+    }
+
+    pub fn rand(srng: &mut SmallRng, distrib: Uniform<f32>) -> Vec2<f32> {
+        Vec2 { x: srng.sample(distrib), y: srng.sample(distrib) }
+    }
+
+}
+
+impl <T> Vec2<T> 
+where T: std::ops::Mul{
+    pub fn new(x: T, y: T) -> Vec2<T> {
+        Vec2{x, y}
+    }
+}
+
+impl <T> Add for Vec2 <T>
+where T: std::ops::Add<Output = T>{
+    type Output = Vec2<T>;
+    fn add(self, other: Vec2<T>) -> Vec2<T> {
+        Vec2 { x: self.x + other.x, y: self.y + other.y }
+    }
+}
+
+impl <T> Mul for Vec2<T> 
+where T: std::ops::Mul<Output = T>{
+    type Output = Vec2<T>;
+    fn mul(self, other: Vec2<T>) -> Vec2<T> {
+        Vec2 {
+            x: self.x * other.x,
+            y: self.y * other.y
+        }
+    }
+}
+
+impl Div<f32> for Vec2<f32>{
+    type Output = Vec2<f32>;
+    fn div(self, other: f32) -> Vec2<f32> {
+        Vec2 {
+            x: 1.0/other * self.x,
+            y: 1.0/other * self.y
+        }
+    }
+}
+
+impl Div<i32> for Vec2<i32>{
+    type Output = Vec2<i32>;
+    fn div(self, other: i32) -> Vec2<i32> {
+        Vec2 {
+            x: self.x / other,
+            y: self.y / other
+        }
+    }
+}
+
+impl <T> Div<Vec2<T>> for Vec2<T> 
+where T: std::ops::Div<Output = T>{
+    type Output = Vec2<T>;
+    fn div(self, other: Vec2<T>) -> Vec2<T> {
+        Vec2 {
+            x: self.x / other.x,
+            y: self.y / other.y
+        }
+    }
+}
+
+impl <T> Display for Vec2<T> 
+where T: Display { // nested type still needs to have Display
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        let str = format!("{} {}", self.x, self.y);
+        fmt.write_str(&str)
+    }
+}
+
 #[derive(Copy, Clone, PartialEq, PartialOrd, Debug)]
 pub struct Vec3{
 	pub x: f32,
@@ -308,6 +398,22 @@ pub struct Rect {
     pub h: i32,
 }
 
+impl Rect{
+    pub fn pos(&self) -> Vec2i {
+        Vec2i {
+            x: self.x,
+            y: self.y, 
+        }
+    }
+
+    pub fn size(&self) -> Vec2i {
+        Vec2i {
+            x: self.w - self.x,
+            y: self.h - self.y,
+        }
+    }
+}
+
 #[cfg(test)]
 mod test{
     use super::*;

src/renderer.rs

@@ -1,275 +1,138 @@
 
-use crate::primitives::{Vec3, Ray, Rect};
+use crate::primitives::{
+    Vec2i,
+    Vec2f,
+    Vec3,
+    Ray,
+    Rect,
+};
 use crate::scene::{
-    Camera,
     Hittable,
+    Scene,
 };
 
-use core::cmp::Ordering;
-use std::thread;
-use std::sync::mpsc;
-use std::ops;
-use rand::Rng;
 use rand::rngs::SmallRng;
-use rand::distributions::Uniform;
-use itertools::Itertools;
 
-// =================
-// Description parts
-// =================
+use itertools::{self, Itertools};
 
-#[derive (Clone)]
-pub struct RenderContext{
-    pub image: (i32, i32),
-    pub samples_per_pixel: u32,
-    pub max_depth: u32,
-    pub world: Hittable,
-    pub camera: Camera,
+const SKY_COLOR: Vec3 = Vec3 { x: 0.5, y: 0.7, z: 1.0};
+
+pub struct RenderProperties {
+    pub samples: u32, // samples are averaged results over a pixel
+    pub bounces: u32, // bounces are how far the ray will travel (in hits not total distance)
 }
 
-pub struct DistributionContianer {
-    pub distrib_zero_one: Uniform<f32>,
-    pub distrib_plusminus_one: Uniform<f32>,
+fn to_uv(coord: Vec2i, img_size: Vec2i) -> Vec2f {
+    let u = (coord.x as f32) / ((img_size.x - 1) as f32);
+    let v = (coord.y as f32) / ((img_size.y - 1) as f32);
+    Vec2f::new(u, v)
 }
 
-impl DistributionContianer {
-    fn new() -> Self {
-        DistributionContianer {
-            distrib_zero_one: Uniform::new(0.0, 1.0),
-            distrib_plusminus_one: Uniform::new(-1.0, 1.0),
-        }
-    }
-}
-
-// =============
-// Drawing Parts
-// =============
-
-fn render_line(y: i32, small_rng: &mut SmallRng, context: RenderContext, distr: &DistributionContianer) -> Vec<Vec3> {
-    //TODO: Ensure that the compiler hoists the distribution's out as constants
-    // else, do so manually
-   (0..context.image.0).map(|x| {
-       sample_pixel(x, y, small_rng, &context, distr)
-    }).collect()
-}
-
-fn ray_color(r: Ray, world: &Hittable, depth: u32, srng: &mut SmallRng, distrib: Uniform<f32> ) -> Vec3 {
-    // recursion depth guard
+fn ray_color(
+    r: Ray, surface: &Hittable, depth: u32,
+    rng: &mut SmallRng,
+) -> Vec3 {
+    // recursion guard
     if depth == 0 {
         return Vec3::zero();
     }
     
-    if let Some(rec) = world.hit(r, 0.001, f32::INFINITY){
+    // cast a ray, interrogate hit record
+    if let Some(record) = surface.hit(r, 0.001, f32::INFINITY){
         let mut scattered = Ray {
             orig: Vec3::zero(),
-            dir: Vec3::zero()
+            dir: Vec3::zero(),
         };
         let mut attenuation = Vec3::zero();
-        match rec.material {
-            Some(mat) => {
-                if mat.scatter(r, rec, &mut attenuation, &mut scattered, srng) {
-                    return attenuation * ray_color(scattered, world, depth-1, srng, distrib);
-                };
-            },
-            None => return Vec3::zero(),
-        }
+        if record.material.scatter(
+            r,
+            &record,
+            &mut attenuation,
+            &mut scattered,
+            rng
+        ) {
+            return attenuation * ray_color(
+                scattered, surface, depth-1, rng
+            );
         }
+    } // TODO: explicit else block
+    // Rust gets angry about the inner if{} block because it evaluates to ()
+    // when the else path is taken. This is a problem for a function
+    // that returns Vec3 and not ().
 
+    { // when nothing is struck, return sky color
         let unitdir = Vec3::as_unit(r.dir);
         let t = 0.5 * (unitdir.y + 1.0);
-    return Vec3::ones() * (1.0 - t) + Vec3::new(0.5, 0.7, 1.0) * t
+        return Vec3::ones() * (1.0 - t) + SKY_COLOR * t
+    }
 }
 
-fn sample_pixel(x: i32, y: i32, small_rng: &mut SmallRng, context: &RenderContext, distr: &DistributionContianer) -> Vec3{
-    (0..context.samples_per_pixel).into_iter().fold(
+fn sample_pixel(
+    coord: Vec2i, // location in image/screen space
+    scene: &Scene,  // scene we're drawing
+    render_props: &RenderProperties,
+    img_size: Vec2i,
+    // Supplied by the execution environment (the thread)
+    rng: &mut SmallRng,
+) -> Vec3{
+    (0..render_props.samples)
+    .fold(
         Vec3::zero(),
-        |color, _sample| {
-            let u = ((x as f32) + small_rng.sample(distr.distrib_zero_one)) / ((context.image.0 - 1) as f32);
-            let v = ((y as f32) + small_rng.sample(distr.distrib_zero_one)) / ((context.image.1 - 1) as f32);
-            let ray = context.camera.get_ray(u, v, small_rng);
-            color + ray_color(ray, &context.world, context.max_depth, small_rng, distr.distrib_plusminus_one)
+        |color, _sample| -> Vec3 {
+            let uv = to_uv(coord, img_size);
+            let ray = scene.camera.get_ray(uv.x, uv.y, rng);
+            if ray.dir.x.is_nan() {
+                panic!("Ray dir.x is NAN");
+            }
+            color + ray_color(ray, &scene.world, render_props.bounces, rng)
         }
     )
 }
 
-// ===============
-// Execution parts
-// ===============
-
-/* Iterable that produces pixels left-to-right, top-to-bottom.
- * `Tile`s represent the render space, not the finished image.
- * There is no internal pixel buffer
- */
-
-type TileCursorIter = itertools::Product<ops::Range<i32>, ops::Range<i32>>;
-
-struct Tile {
-    bounds: Rect,
-    context: RenderContext,
-    small_rng: SmallRng,
-    rand_distr: DistributionContianer,
-    cursor: TileCursorIter,
+pub struct Tile {
+    _bounds: Rect,
+    pub pixels: Vec<Vec3>,
 }
 
-impl Tile{
-    fn new(
-        bounds: Rect,
-        context: RenderContext,
-        small_rng: SmallRng,
-        rand_distr: DistributionContianer
-    ) -> Self
-    {
-        Tile { bounds, context, small_rng, rand_distr,
-            cursor: (bounds.x..(bounds.x + bounds.w))
-                .cartesian_product(bounds.y..(bounds.y + bounds.h)
+impl Tile {
+    pub fn render_tile(
+        bounds: Rect,       // bounds of the region to render
+        img_size: Vec2i,    // final image resolution (needed for proper UV mapping)
+        scene: &Scene,
+        properties: &RenderProperties, // TODO: Place image size in render properties?
+        rng: &mut SmallRng,
+    ) -> Self {
+        let pixel_iter = (bounds.y..(bounds.y + bounds.h))
+            .cartesian_product( bounds.x..(bounds.x + bounds.w));
+        let pixels = pixel_iter.map(
+            |coord| -> Vec3 {
+                sample_pixel(
+                    Vec2i{x: coord.1, y: coord.0},
+                    scene,
+                    properties,
+                    img_size,
+                    rng,
                 )
             }
-
-    }
-}
-
-impl Iterator for Tile {
-    type Item = Vec3;
-    fn next(&mut self) -> Option<Self::Item> {
-        if let Some((x, y)) = self.cursor.next(){
-            Some(sample_pixel(
-                x, y,
-                &mut self.small_rng,
-                &self.context,
-                &self.rand_distr,
-            ))
-        } else {
-            None
+        ).collect();
+        Self {
+            _bounds: bounds,
+            pixels
         }
     }
-}
-
-
-
-#[derive (Clone)]
-pub enum RenderCommand{
-    Stop,
-    Line { line_num: i32, context: RenderContext },
-}
-
-pub struct RenderResult {
-    pub line_num: i32,
-    pub line: Vec<Vec3>,
-}
-
-impl Ord for RenderResult {
-    fn cmp(&self, other: &Self) -> Ordering {
-        if self.line_num > other.line_num {
-            Ordering::Less
-        } else if self.line_num < other.line_num {
-            Ordering::Greater
-        } else {
-            Ordering::Equal
-        }
-    }
-}
-
-impl PartialOrd for RenderResult {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        Some(self.cmp(other))
-    }
-}
-
-impl PartialEq for RenderResult {
-    fn eq(&self, other: &Self) -> bool {
-        self.line_num == other.line_num
-    }
-}
-
-impl Eq for RenderResult {}
-
-/*
- *  The dispatcher will hold a list of threads, and a list of command input channels to match.
- *  Helper functions exist to input jobs serially, and then dispatch them to an open thread.
- *
- *  Since receivers can be matched to several senders, the input end of the result channel will
- *  be cloned and given to each of the threads.
- *  TODO: Consider holding a copy of the render_tx end in case threads exit early and need to
- *  be restored.
- */
-pub struct Dispatcher{
-    handles: Vec<thread::JoinHandle<()>>,
-    command_transmitters: Vec<mpsc::SyncSender<RenderCommand>>, 
-    next_to_feed: usize, // gonna do a round-robin style dispatch, ig.
-}
-
-impl Dispatcher {
-    pub fn new(srng: &SmallRng, num_threads: usize) -> (Dispatcher, mpsc::Receiver<RenderResult> ) {
-        let mut handles = Vec::new();
-        let mut command_transmitters = Vec::<mpsc::SyncSender<RenderCommand>>::new();
-
-        let (render_tx, render_rx) = mpsc::sync_channel::<RenderResult>(1);
-
-        for _ in 0..num_threads {
-            // create new command tx/rx pairs. Store tx in the list, give rx to the thread.
-            let (command_tx, command_rx) = mpsc::sync_channel::<RenderCommand>(1);
-            // TODO: Pick appropriate command queue depth (or make it controllable, even)
-
-
-            let mut srng = srng.clone();
-            let threads_result_tx = render_tx.clone();
-            let distribs = DistributionContianer::new();
-            let thread_handle = thread::spawn(move || {
-                while let Ok(job) = command_rx.recv() {
-                    match job {
-                        RenderCommand::Stop => {
-                            break;
-                        }
-                        RenderCommand::Line { line_num, context } => {
-                            let line = render_line(line_num, &mut srng, context, &distribs);
-                            let result = RenderResult { line_num, line };
-                            threads_result_tx.send(result).unwrap();
-                        }
-                    }
-                }
-            });
-            handles.push(thread_handle);
-            command_transmitters.push(command_tx);
-        }
-        // finally, stash everything in the Dispatcher struct and return.
-        (
-            Dispatcher{
-                handles,
-                command_transmitters,
-                next_to_feed: 0,
-            },
-            render_rx
+    pub fn render_line(
+        y: i32, // bounding rect and line
+        img_size: Vec2i,
+        scene: &Scene,
+        properties: &RenderProperties,
+        rng: &mut SmallRng, // rng utils
+    ) -> Self {
+        Tile::render_tile(
+            Rect{ x: 0, y, w: img_size.x, h: 1 },
+            img_size,
+            scene,
+            properties,
+            rng
         )
     }
-
-    //TODO: Reconsider round-robin dispatch
-    // When passing the message to threads which are still busy, this function
-    // will block (it's a sync_channel). While blocked, other threads could
-    // become available and left idle.
-    pub fn submit_job(&mut self, command: RenderCommand) -> Result<(), mpsc::SendError<RenderCommand>> {
-        // Stop command is special. We'll broadcast it to all threads.
-        if let RenderCommand::Stop = command {
-            for channel in &self.command_transmitters {
-                return channel.send(command.clone());
-            }
-        }
-
-        // Check that `next_to_feed` is in-bounds, and then insert.
-        // index is post-incremented with this function call.
-
-        // wrap when at length (0-indexed so last valid index is len-1)
-        if self.next_to_feed == self.handles.len() {
-            self.next_to_feed = 0;
-        } else if self.next_to_feed > self.handles.len() {
-            panic!("How the hell did a +=1 skip past the maximum allowed size?");
-        }
-
-        match self.command_transmitters.get(self.next_to_feed){
-            Some(target) => target.send(command).unwrap(),
-            None => panic!("oh god oh fuck"),
-        }
-        self.next_to_feed += 1;
-        Ok(())
-    }
 }
-

src/scene.rs

@@ -8,7 +8,7 @@ use rand::distributions::Uniform;
 pub struct HitRecord{
     pub p: Vec3,
     pub normal: Vec3,
-    pub material: Option<Material>,
+    pub material: Material,
     pub t: f32,
     pub front_face: bool,
 }
@@ -22,7 +22,7 @@ impl HitRecord{
 
 #[derive (Clone)]
 pub enum Hittable {
-    Sphere { center: Vec3, radius: f32, material: Option<Material> },
+    Sphere { center: Vec3, radius: f32, material: Material },
     HittableList { hittables: Vec<Hittable> }
 }
 
@@ -30,24 +30,15 @@ impl Hittable {
     pub fn hit(&self, r: Ray, t_min: f32, t_max: f32) -> Option<HitRecord> {
         match self {
             Hittable::HittableList { hittables } => {
-                let mut might_return = HitRecord {
-                    p: Vec3::zero(),
-                    normal: Vec3::zero(),
-                    material: None,
-                    t: t_max,
-                    front_face: false,
-                };
-                let mut hit_anything = false;
-
-                for item in hittables {
-                    if let Some(record) = item.hit(r, t_min, might_return.t){
-                        hit_anything = true;
-                        might_return = record;
-                    }
-                }
-                if hit_anything{
-                    return Some(might_return);
-                } else { return None; }
+                hittables.iter()
+                .map( |obj| -> Option<HitRecord> {
+                    obj.hit(r, t_min, t_max)
+                }).filter(|obj| obj.is_some())
+                .min_by(|lhs, rhs| {
+                    let lhs = lhs.as_ref().unwrap();
+                    let rhs = rhs.as_ref().unwrap();
+                    lhs.t.partial_cmp(&rhs.t).expect("Couldn't compare??")
+                }).unwrap_or(None)
             }
 
             Hittable::Sphere { center, radius, material } => {
@@ -102,7 +93,7 @@ impl Material {
     pub fn scatter(
         &self,
         ray_in: Ray,
-        rec: HitRecord,
+        rec: &HitRecord,
         attenuation: &mut Vec3,
         scattered: &mut Ray,
         srng: &mut SmallRng,
@@ -178,7 +169,6 @@ pub fn degrees_to_radians(degrees: f32) -> f32 {
     degrees * std::f32::consts::PI / 180.0
 }
 
-#[derive (Clone, Copy)]
 pub struct Camera {
     origin: Vec3,
     lower_left_corner: Vec3,
@@ -237,3 +227,92 @@ impl Camera {
     }
 }
 
+
+pub struct Scene {
+    pub camera: Camera,
+    pub world: Hittable,
+}
+
+impl Scene {
+    pub fn random_world(srng: &mut SmallRng) -> Hittable {
+        let mat_ground = Material::Lambertian { albedo: Vec3::new(0.5, 0.5, 0.5) };
+        let mut world = Hittable::HittableList { hittables : Vec::<Hittable>::new() };
+        
+        world.push( Hittable::Sphere { center: Vec3::new(0.0, -1000.0, 0.0), radius: 1000.0, material: mat_ground });
+        
+        let distrib_zero_one = Uniform::new(0.0, 1.0);
+        for a in -11..11 {
+            for b in -11..11 {
+                let choose_mat = srng.sample(distrib_zero_one);
+                let center = Vec3 {
+                    x: a as f32 + 0.9 * srng.sample(distrib_zero_one),
+                    y: 0.2,
+                    z: b as f32 + 0.9 * srng.sample(distrib_zero_one),
+                };
+                if (center - Vec3::new(4.0, 0.2, 0.0)).length() > 0.9 {
+
+                    if choose_mat < 0.8 {
+                        // diffuse
+                        let albedo = Vec3::rand(srng, distrib_zero_one) * Vec3::rand(srng, distrib_zero_one);
+                        let sphere_material = Material::Lambertian { albedo };
+                        world.push(
+                            Hittable::Sphere {
+                                center,
+                                radius: 0.2,
+                                material: sphere_material,
+                            }
+                        );
+                    } else if choose_mat < 0.95 {
+                        // metal
+                        let distr_albedo = Uniform::new(0.5, 1.0);
+                        let distr_fuzz = Uniform::new(0.0, 0.5);
+
+                        let albedo = Vec3::rand(srng, distr_albedo);
+                        let fuzz = srng.sample(distr_fuzz);
+                        let material = Material::Metal { albedo, fuzz };
+                        world.push(
+                            Hittable::Sphere {
+                                center,
+                                radius: 0.2,
+                                material: material,
+                            }
+                        );
+                    } else {
+                        // glass
+                        let material = Material::Dielectric { index_refraction: 1.5 };
+                        world.push(
+                            Hittable::Sphere{
+                                center,
+                                radius: 0.2,
+                                material: material,
+                            }
+                        );
+
+                    };
+                }
+            }
+        }
+
+        let material1 = Material::Dielectric { index_refraction: 1.5 };
+        world.push( Hittable::Sphere{
+            center: Vec3::new(0.0, 1.0, 0.0),
+            radius: 1.0,
+            material: material1
+        });
+
+        let material2 = Material::Lambertian { albedo: Vec3::new(0.4, 0.2, 0.1) };
+        world.push( Hittable::Sphere {
+            center: Vec3::new(-4.0, 1.0, 0.0),
+            radius: 1.0,
+            material: material2
+        });
+
+        let material3 = Material::Metal { albedo: Vec3::new(0.7, 0.6, 0.5), fuzz: 0.0 };
+        world.push( Hittable::Sphere {
+            center: Vec3::new(4.0, 1.0, 0.0),
+            radius: 1.0,
+            material: material3
+        });
+        world
+    }
+}