project: justify every dependency

hemisphere sampling previously could return infinite, producing NaNs
when later multiplying that weight by 0.

.cargo/config

@@ -0,0 +1,2 @@
+[build]
+rustflags = ["-C", "target-cpu=native"]

.rustfmt.toml

@@ -52,7 +52,6 @@ use_field_init_shorthand = false
 force_explicit_abi = true
 condense_wildcard_suffixes = false
 color = "Auto"
-required_version = "1.4.12"
 unstable_features = false
 disable_all_formatting = false
 skip_children = false

Cargo.toml

@@ -4,3 +4,7 @@ members = [
     "beevee",
     "pathtracer",
 ]
+
+[profile.release]
+lto = true
+codegen-units = 1

beevee/Cargo.toml

@@ -7,5 +7,8 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+# Linear algebra basic operations and types
 nalgebra = "0.20"
+
+# High performance quicksort/quickselect
 pdqselect = "0.1.0"

beevee/src/bvh/accelerated.rs

@@ -0,0 +1,39 @@
+use super::Intersected;
+use crate::aabb::Bounded;
+use crate::ray::Ray;
+
+/// The trait for any mesh-like object to be used in the [`BVH`]. If your object is not an
+/// aggregate, you should instead implement [`Intersected`] which derives this trait automatically.
+///
+/// This trait is there to accomodate for aggregate objects inside the [`BVH`]: you can implement a
+/// faster look-up of information using a [`BVH`] in a mesh for example, returning directly the
+/// reference to a hit triangle. This enables us to return this triangle instead of returning a
+/// reference to the whole mesh.
+///
+/// [`BVH`]: struct.BVH.html
+/// [`Intersected`]: struct.Intersected.html
+pub trait Accelerated: Bounded {
+    /// The type contained in your [`Accelerated`] structure
+    ///
+    /// [`Accelerated`]: struct.Accelerated.html
+    type Output;
+
+    /// Return None if no intersection happens with the ray, or a tuple of distance along the ray
+    /// and a reference to the object that was hit.
+    fn intersect(&self, ray: &Ray) -> Option<(f32, &Self::Output)>;
+}
+
+/// The automatic implementation for any [`Intersected`] object to be used in the [`BVH`].
+///
+/// [`BVH`]: struct.BVH.html
+impl<T> Accelerated for T
+where
+    T: Intersected,
+{
+    type Output = Self;
+
+    /// Return a reference to `self` when a distance was found.
+    fn intersect(&self, ray: &Ray) -> Option<(f32, &Self::Output)> {
+        self.intersect(ray).map(|t| (t, self))
+    }
+}

beevee/src/bvh/intersected.rs

@@ -1,8 +1,11 @@
 use crate::aabb::Bounded;
 use crate::ray::Ray;
 
-/// The trait for any object to be used in the [`BVH`].
+/// The trait for any object to be used in the [`BVH`]. Its derivation for [`Accelerated`] is
+/// automatically derived to return a reference to itself. If this not the intended semantics, see
+/// [`Accelerated`].
 ///
+/// [`Accelerated`]: struct.Accelerated.html
 /// [`BVH`]: struct.BVH.html
 pub trait Intersected: Bounded {
     /// Return None if there is no intersection, or the distance along the ray to the closest

beevee/src/bvh/mod.rs

@@ -1,5 +1,8 @@
 //! The Boudning Volume Hiearchy
 
+mod accelerated;
+pub use accelerated::*;
+
 mod intersected;
 pub use intersected::*;
 

beevee/src/bvh/tree.rs

@@ -1,4 +1,4 @@
-use super::Intersected;
+use super::Accelerated;
 use crate::aabb::AABB;
 use crate::ray::Ray;
 use crate::Axis;
@@ -23,9 +23,9 @@ struct Node {
 }
 
 /// The BVH containing all the objects of type O.
-/// This type must implement [`Intersected`].
+/// This type must implement [`Accelerated`].
 ///
-/// [`Intersected`]: trait.Intersected.html
+/// [`Accelerated`]: trait.Accelerated.html
 #[derive(Clone, Debug, PartialEq)]
 pub struct BVH {
     tree: Node,
@@ -92,7 +92,7 @@ impl BVH {
     /// let spheres: &mut [Sphere] = &mut [Sphere{ center: Point::origin(), radius: 2.5 }];
     /// let bvh = BVH::build(spheres);
     /// ```
-    pub fn build<O: Intersected>(objects: &mut [O]) -> Self {
+    pub fn build<O: Accelerated>(objects: &mut [O]) -> Self {
         Self::with_max_capacity(objects, 32)
     }
 
@@ -157,7 +157,7 @@ impl BVH {
     /// let spheres: &mut [Sphere] = &mut [Sphere{ center: Point::origin(), radius: 2.5 }];
     /// let bvh = BVH::with_max_capacity(spheres, 32);
     /// ```
-    pub fn with_max_capacity<O: Intersected>(objects: &mut [O], max_cap: usize) -> Self {
+    pub fn with_max_capacity<O: Accelerated>(objects: &mut [O], max_cap: usize) -> Self {
         let tree = build_node(objects, 0, objects.len(), max_cap);
         Self { tree }
     }
@@ -226,8 +226,8 @@ impl BVH {
     /// let bvh = BVH::with_max_capacity(spheres, 32);
     /// assert!(bvh.is_sound(spheres));
     /// ```
-    pub fn is_sound<O: Intersected>(&self, objects: &[O]) -> bool {
-        fn check_node<O: Intersected>(objects: &[O], node: &Node) -> bool {
+    pub fn is_sound<O: Accelerated>(&self, objects: &[O]) -> bool {
+        fn check_node<O: Accelerated>(objects: &[O], node: &Node) -> bool {
             if node.begin > node.end {
                 return false;
             }
@@ -322,17 +322,21 @@ impl BVH {
     /// assert_eq!(dist, 0.5);
     /// assert_eq!(obj, &spheres[0]);
     /// ```
-    pub fn walk<'o, O: Intersected>(&self, ray: &Ray, objects: &'o [O]) -> Option<(f32, &'o O)> {
+    pub fn walk<'o, O: Accelerated>(
+        &self,
+        ray: &Ray,
+        objects: &'o [O],
+    ) -> Option<(f32, &'o O::Output)> {
         walk_rec_helper(ray, objects, &self.tree, std::f32::INFINITY)
     }
 }
 
-fn walk_rec_helper<'o, O: Intersected>(
+fn walk_rec_helper<'o, O: Accelerated>(
     ray: &Ray,
     objects: &'o [O],
     node: &Node,
     min: f32,
-) -> Option<(f32, &'o O)> {
+) -> Option<(f32, &'o O::Output)> {
     use std::cmp::Ordering;
 
     match &node.kind {
@@ -340,7 +344,7 @@ fn walk_rec_helper<'o, O: Intersected>(
         NodeEnum::Leaf => objects[node.begin..node.end]
             .iter()
             // This turns the Option<f32> of an intersection into an Option<(f32, &O)>
-            .filter_map(|o| o.intersect(ray).map(|d| (d, o)))
+            .filter_map(|o| o.intersect(ray))
             // Discard values that are too far away
             .filter(|(dist, _)| dist < &min)
             // Only keep the minimum value, if there is one
@@ -382,14 +386,14 @@ fn walk_rec_helper<'o, O: Intersected>(
     }
 }
 
-fn bounds_from_slice<O: Intersected>(objects: &[O]) -> AABB {
+fn bounds_from_slice<O: Accelerated>(objects: &[O]) -> AABB {
     objects
         .iter()
         .map(|o| o.aabb())
         .fold(AABB::empty(), |acc, other| acc.union(&other))
 }
 
-fn build_node<O: Intersected>(objects: &mut [O], begin: usize, end: usize, max_cap: usize) -> Node {
+fn build_node<O: Accelerated>(objects: &mut [O], begin: usize, end: usize, max_cap: usize) -> Node {
     let aabb = bounds_from_slice(objects);
     // Don't split nodes under capacity
     if objects.len() <= max_cap {
@@ -401,7 +405,7 @@ fn build_node<O: Intersected>(objects: &mut [O], begin: usize, end: usize, max_c
         };
     }
     // Calculate the SAH heuristic for this slice
-    let (split, axis, cost) = compute_sah(&mut objects[begin..end], aabb.surface(), max_cap);
+    let (split, axis, cost) = compute_sah(objects, aabb.surface(), max_cap);
     // Only split if the heuristic shows that it is worth it
     if cost >= objects.len() as f32 {
         return Node {
@@ -411,11 +415,11 @@ fn build_node<O: Intersected>(objects: &mut [O], begin: usize, end: usize, max_c
             kind: NodeEnum::Leaf,
         };
     }
-    // Avoid degenerate cases, and recenter the split inside [begin, end)
-    let split = if split == 0 || split >= (end - begin - 1) {
-        begin + (end - begin) / 2
+    // Avoid degenerate cases
+    let split = if split <= 1 || split >= (objects.len() - 1) {
+        (end - begin) / 2
     } else {
-        begin + split
+        split
     };
     // Project along chosen axis
     pdqselect::select_by(objects, split, |lhs, rhs| {
@@ -424,8 +428,18 @@ fn build_node<O: Intersected>(objects: &mut [O], begin: usize, end: usize, max_c
             .expect("Can't use Nans in the SAH computation")
     });
     // Construct children recurivsely on [begin, split) and [split, end)
-    let left = Box::new(build_node(objects, begin, split, max_cap));
-    let right = Box::new(build_node(objects, split, end, max_cap));
+    let left = Box::new(build_node(
+        &mut objects[0..split],
+        begin,
+        begin + split,
+        max_cap,
+    ));
+    let right = Box::new(build_node(
+        &mut objects[split..],
+        begin + split,
+        end,
+        max_cap,
+    ));
     // Build the node recursivelly
     Node {
         bounds: aabb,
@@ -437,7 +451,7 @@ fn build_node<O: Intersected>(objects: &mut [O], begin: usize, end: usize, max_c
 
 /// Returns the index at which to split for SAH, the Axis along which to split, and the calculated
 /// cost.
-fn compute_sah<O: Intersected>(
+fn compute_sah<O: Accelerated>(
     objects: &mut [O],
     surface: f32,
     max_cap: usize,
@@ -481,7 +495,7 @@ fn compute_sah<O: Intersected>(
 
             let cost = 1. / max_cap as f32
                 + (left_count as f32 * left_surfaces[left_count - 1]
-                    + right_count as f32 * right_surfaces[right_count])
+                    + right_count as f32 * right_surfaces[right_count - 1])
                     / surface;
 
             if cost < min {

pathtracer/Cargo.toml

@@ -19,20 +19,44 @@ name = "pathtracer"
 path = "src/main.rs"
 
 [dependencies]
+# Our own BVH implementation
 beevee = { path = "../beevee" }
+
+# Macro to implement arithmetic operators automagically
 derive_more = "0.99.3"
+
+# Transform interfaces into enums for better performance than dynamic dispatch
 enum_dispatch = "0.2.1"
+
+# Save an image to PNG
 image = "0.23.0"
-indicatif = "0.14.0"
+
+# Random implementation, not part of the standard library in Rust
 rand = "0.7"
+
+# Parallelism utility functions
 rayon = "1.3.0"
+
+# YAML deserialization
 serde_yaml = "0.8"
+
+# Command-line argument parsing utilities
 structopt = "0.3"
 
+# OBJ format parser
+tobj = "1.0"
+
+# Fancy terminal progress bar
+[dependencies.indicatif]
+version = "0.14"
+features = ["with_rayon"]
+
+# Linear algebra basic operations and types
 [dependencies.nalgebra]
 version = "0.20.0"
 features = ["serde-serialize"]
 
+# YAML deserialization
 [dependencies.serde]
 version = "1.0"
 features = ["derive"]

pathtracer/examples/colorful.yaml

@@ -1,5 +1,5 @@
 # Optional field
-aliasing_limit: 10
+shot_rays: 10
 # Optional field
 reflection_limit: 5
 

pathtracer/examples/cornell-box.yaml

@@ -0,0 +1,29 @@
+reflection_limit: 5
+shot_rays: 50
+
+camera:
+  origin: [0.0, 1.0, 0.0]
+  forward: [ 0.0, 0.0, 1.0]
+  up: [0.0, 1.0, 0.0]
+  fov: 60.0
+  distance_to_image: 1.0
+  x: 1080
+  y: 1080
+
+lights:
+  ambients:
+    - color: {r: 0.1, g: 0.1, b: 0.1}
+  points:
+    - position: [0.0, 1.95, 3.2]
+      color: {r: 1.0, g: 1.0, b: 1.0}
+
+meshes:
+  # FIXME: make the path relative to the YAML in some way?
+  # Easiest solution would be to chdir to the YAML's directory
+  - obj_file: "pathtracer/examples/objs/cornell-box.obj"
+    translation: [0.0, 0.0, 2.8]
+    rotation: [0, 180, 0]
+
+steps:
+  - 10
+  - 25

pathtracer/examples/objs/cornell-box.mtl

@@ -0,0 +1,88 @@
+# The original Cornell Box in OBJ format.
+# Note that the real box is not a perfect cube, so
+# the faces are imperfect in this data set.
+#
+# Created by Guedis Cardenas and Morgan McGuire at Williams College, 2011
+# Released into the Public Domain.
+#
+# http://graphics.cs.williams.edu/data
+# http://www.graphics.cornell.edu/online/box/data.html
+#
+
+newmtl leftWall
+  Ns 10.0000
+  Ni 1.5000
+  illum 2
+  Ka 0.63 0.065 0.05 # Red
+  Kd 0.63 0.065 0.05
+  Ks 0 0 0
+  Ke 0 0 0
+
+
+newmtl rightWall
+  Ns 10.0000
+  Ni 1.5000
+  illum 2
+  Ka 0.14 0.45 0.091 # Green
+  Kd 0.14 0.45 0.091
+  Ks 0 0 0
+  Ke 0 0 0
+
+
+newmtl floor
+  Ns 10.0000
+  Ni 1.0000
+  illum 2
+  Ka 0.725 0.71 0.68 # White
+  Kd 0.725 0.71 0.68
+  Ks 0 0 0
+  Ke 0 0 0
+
+
+newmtl ceiling
+  Ns 10.0000
+  Ni 1.0000
+  illum 2
+  Ka 0.725 0.71 0.68 # White
+  Kd 0.725 0.71 0.68
+  Ks 0     0    0
+  Ke 0     0    0
+
+
+newmtl backWall
+  Ns 10.0000
+  Ni 1.0000
+  illum 2
+  Ka 0.725 0.71 0.68 # White
+  Kd 0.725 0.71 0.68
+  Ks 0 0 0
+  Ke 0 0 0
+
+
+newmtl shortBox
+  Ns 10.0000
+  Ni 1.0000
+  illum 2
+  Ka 0.725 0.71 0.68 # White
+  Kd 0.725 0.71 0.68
+  Ks 0 0 0
+  Ke 0 0 0
+
+
+newmtl tallBox
+  Ns 10.0000
+  Ni 1.0000
+  illum 2
+  Ka 0.725 0.71 0.68 # White
+  Kd 0.725 0.71 0.68
+  Ks 0 0 0
+  Ke 0 0 0
+
+newmtl light
+  Ns 10.0000
+  Ni 1.0000
+  illum 2
+  Ka 0.78 0.78 0.78 # White
+  Kd 0.78 0.78 0.78
+  Ks 0 0 0
+  Ke 17 12 4

pathtracer/examples/objs/cornell-box.obj

@@ -0,0 +1,168 @@
+# The original Cornell Box in OBJ format.
+# Note that the real box is not a perfect cube, so
+# the faces are imperfect in this data set.
+#
+# Created by Guedis Cardenas and Morgan McGuire at Williams College, 2011
+# Released into the Public Domain.
+#
+# http://graphics.cs.williams.edu/data
+# http://www.graphics.cornell.edu/online/box/data.html
+#
+
+mtllib cornell-box.mtl
+
+## Object floor
+v  -1.01  0.00   0.99
+v   1.00  0.00   0.99
+v   1.00  0.00  -1.04
+v  -0.99  0.00  -1.04
+
+g floor
+usemtl floor
+f -4 -3 -2 -1
+
+## Object ceiling
+v  -1.02  1.99   0.99
+v  -1.02  1.99  -1.04
+v   1.00  1.99  -1.04
+v   1.00  1.99   0.99
+
+g ceiling
+usemtl ceiling
+f -4 -3 -2 -1
+
+## Object backwall
+v  -0.99  0.00  -1.04
+v   1.00  0.00  -1.04
+v   1.00  1.99  -1.04
+v  -1.02  1.99  -1.04
+
+g backWall
+usemtl backWall
+f -4 -3 -2 -1
+
+## Object rightwall
+v	1.00  0.00  -1.04
+v	1.00  0.00   0.99
+v	1.00  1.99   0.99
+v	1.00  1.99  -1.04
+
+g rightWall
+usemtl rightWall
+f -4 -3 -2 -1
+
+## Object leftWall
+v  -1.01  0.00   0.99
+v  -0.99  0.00  -1.04
+v  -1.02  1.99  -1.04
+v  -1.02  1.99   0.99
+
+g leftWall
+usemtl leftWall
+f -4 -3 -2 -1
+
+## Object shortBox
+usemtl shortBox
+
+# Top Face
+v	0.53  0.60   0.75
+v	0.70  0.60   0.17
+v	0.13  0.60   0.00
+v  -0.05  0.60   0.57
+f -4 -3 -2 -1
+
+# Left Face
+v  -0.05  0.00   0.57
+v  -0.05  0.60   0.57
+v   0.13  0.60   0.00
+v   0.13  0.00   0.00
+f -4 -3 -2 -1
+
+# Front Face
+v	0.53  0.00   0.75
+v	0.53  0.60   0.75
+v  -0.05  0.60   0.57
+v  -0.05  0.00   0.57
+f -4 -3 -2 -1
+
+# Right Face
+v	0.70  0.00   0.17
+v	0.70  0.60   0.17
+v	0.53  0.60   0.75
+v	0.53  0.00   0.75
+f -4 -3 -2 -1
+
+# Back Face
+v	0.13  0.00   0.00
+v	0.13  0.60   0.00
+v	0.70  0.60   0.17
+v	0.70  0.00   0.17
+f -4 -3 -2 -1
+
+# Bottom Face
+v	0.53  0.00   0.75
+v	0.70  0.00   0.17
+v	0.13  0.00   0.00
+v  -0.05  0.00   0.57
+f -12 -11 -10 -9
+
+g shortBox
+usemtl shortBox
+
+## Object tallBox
+usemtl tallBox
+
+# Top Face
+v	-0.53  1.20   0.09
+v	 0.04  1.20  -0.09
+v	-0.14  1.20  -0.67
+v	-0.71  1.20  -0.49
+f -4 -3 -2 -1
+
+# Left Face
+v	-0.53  0.00   0.09
+v	-0.53  1.20   0.09
+v	-0.71  1.20  -0.49
+v	-0.71  0.00  -0.49
+f -4 -3 -2 -1
+
+# Back Face
+v	-0.71  0.00  -0.49
+v	-0.71  1.20  -0.49
+v	-0.14  1.20  -0.67
+v	-0.14  0.00  -0.67
+f -4 -3 -2 -1
+
+# Right Face
+v	-0.14  0.00  -0.67
+v	-0.14  1.20  -0.67
+v	 0.04  1.20  -0.09
+v	 0.04  0.00  -0.09
+f -4 -3 -2 -1
+
+# Front Face
+v	 0.04  0.00  -0.09
+v	 0.04  1.20  -0.09
+v	-0.53  1.20   0.09
+v	-0.53  0.00   0.09
+f -4 -3 -2 -1
+
+# Bottom Face
+v	-0.53  0.00   0.09
+v	 0.04  0.00  -0.09
+v	-0.14  0.00  -0.67
+v	-0.71  0.00  -0.49
+f -8 -7 -6 -5
+
+g tallBox
+usemtl tallBox
+
+## Object light
+v	-0.24  1.98   0.16
+v	-0.24  1.98  -0.22
+v	 0.23  1.98  -0.22
+v	 0.23  1.98   0.16
+
+g light
+usemtl light
+f -4 -3 -2 -1

pathtracer/examples/scene.yaml

@@ -1,4 +1,4 @@
-aliasing_limit: 10
+shot_rays: 10
 reflection_limit: 5
 background: {r: 0.5, g: 0.5, b: 0.5}
 

pathtracer/src/core/camera.rs

@@ -2,13 +2,18 @@
 
 use super::film::Film;
 use crate::{Point, Vector};
-use serde::{Deserialize, Deserializer};
+use beevee::ray::Ray;
+use nalgebra::Unit;
+use serde::Deserialize;
 
 /// Represent an abstract camera to observe the scene.
-#[derive(Debug, PartialEq)]
+#[serde(from = "SerializedCamera")]
+#[derive(Debug, PartialEq, Deserialize)]
 pub struct Camera {
-    /// Where the camera is set in the scene (i.e: its focal point).
+    /// Where the camera is set in the scene (i.e: the center of the lens).
     origin: Point,
+    /// How far away is the camera's focal plane.
+    distance_to_image: f32,
     /// The film to represent each pixel in the scene.
     film: Film,
 }
@@ -37,15 +42,20 @@ impl Camera {
         forward: Vector,
         up: Vector,
         fov: f32,
-        dist_to_image: f32,
+        distance_to_image: f32,
         x: u32,
         y: u32,
     ) -> Self {
         let right = forward.cross(&up);
-        let center = origin + forward.normalize() * dist_to_image;
-        let screen_size = 2. * f32::tan(fov / 2.) * dist_to_image;
-        let film = Film::new(x, y, screen_size, center, up, right);
-        Camera { origin, film }
+        let screen_size = 2. * f32::tan(fov / 2.);
+        // Construct the film behind the camera, upside down
+        let center = origin - forward.normalize();
+        let film = Film::new(x, y, screen_size, center, -up, -right);
+        Camera {
+            origin,
+            distance_to_image,
+            film,
+        }
     }
 
     /// Get the `Camera`'s [`Film`].
@@ -78,6 +88,24 @@ impl Camera {
     pub fn origin(&self) -> &Point {
         &self.origin
     }
+
+    /// Get the Ray coming out of the camera at a given ratio on the image.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use pathtracer::core::Camera;
+    /// # use pathtracer::Point;
+    /// #
+    /// let cam = Camera::default();
+    /// let ray_ul = cam.ray_with_ratio(0., 0.); // Ray coming out of the upper-left pixel
+    /// let ray_ul = cam.ray_with_ratio(1., 1.); // Ray coming out of the lower-right pixel
+    /// ```
+    pub fn ray_with_ratio(&self, x: f32, y: f32) -> Ray {
+        let pixel = self.film().pixel_at_ratio(x, y);
+        let direction = Unit::new_normalize(self.origin() - pixel);
+        Ray::new(pixel, direction)
+    }
 }
 
 impl Default for Camera {
@@ -140,16 +168,6 @@ impl From<SerializedCamera> for Camera {
     }
 }
 
-impl<'de> Deserialize<'de> for Camera {
-    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    where
-        D: Deserializer<'de>,
-    {
-        let cam: SerializedCamera = Deserialize::deserialize(deserializer)?;
-        Ok(cam.into())
-    }
-}
-
 #[cfg(test)]
 mod test {
     use super::*;
@@ -157,7 +175,7 @@ mod test {
     #[test]
     fn new_works() {
         let cam = Camera::new(
-            Point::new(-1., 0., 0.),
+            Point::new(1., 0., 0.),
             Vector::new(1., 0., 0.),
             Vector::new(0., 1., 0.),
             2. * f32::atan(1.), /* 90° in radian */
@@ -168,14 +186,15 @@ mod test {
         assert_eq!(
             cam,
             Camera {
-                origin: Point::new(-1., 0., 0.),
+                origin: Point::new(1., 0., 0.),
+                distance_to_image: 1.,
                 film: Film::new(
                     1080,
                     1080,
                     2.,
                     Point::origin(),
-                    Vector::new(0., 1., 0.),
-                    Vector::new(0., 0., 1.),
+                    -Vector::new(0., 1., 0.),
+                    -Vector::new(0., 0., 1.),
                 )
             }
         )
@@ -184,7 +203,7 @@ mod test {
     #[test]
     fn deserialization_works() {
         let yaml = r#"
-            origin: [-1.0, 0.0, 0.0]
+            origin: [1.0, 0.0, 0.0]
             forward: [ 1.0, 0.0, 0.0]
             up: [0.0, 1.0, 0.0]
             fov: 90.0
@@ -196,14 +215,15 @@ mod test {
         assert_eq!(
             cam,
             Camera {
-                origin: Point::new(-1., 0., 0.),
+                origin: Point::new(1., 0., 0.),
+                distance_to_image: 1.0,
                 film: Film::new(
                     1080,
                     1080,
                     2.,
                     Point::origin(),
-                    Vector::new(0., 1., 0.),
-                    Vector::new(0., 0., 1.),
+                    -Vector::new(0., 1., 0.),
+                    -Vector::new(0., 0., 1.),
                 )
             }
         )

pathtracer/src/core/color.rs

@@ -70,6 +70,25 @@ impl LinearColor {
         LinearColor { r, g, b }
     }
 
+    /// Creates a new `Color` from a slice.
+    ///
+    /// Panics if slice has less than 3 elements.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use pathtracer::core::LinearColor;
+    /// #
+    /// let color = LinearColor::from_slice(&[1.0, 0.0, 0.0]); // bright red!
+    /// ```
+    pub fn from_slice(s: &[f32]) -> Self {
+        LinearColor {
+            r: s[0],
+            g: s[1],
+            b: s[2],
+        }
+    }
+
     #[must_use]
     /// Clamps the color's RGB components between 0.0 and 1.0.
     ///

pathtracer/src/core/light_properties.rs

@@ -33,6 +33,9 @@ pub struct LightProperties {
     /// The transparency or reflectivity properties.
     #[serde(flatten)]
     pub refl_trans: Option<ReflTransEnum>,
+    /// The emitted light from this object, only used for path-tracing rendering techniques
+    #[serde(default)]
+    pub emitted: LinearColor,
 }
 
 impl LightProperties {
@@ -48,17 +51,20 @@ impl LightProperties {
     ///     LinearColor::new(0.25, 0.5, 1.),
     ///     LinearColor::new(0.75, 0.375, 0.125),
     ///     Some(ReflTransEnum::Reflectivity { coef: 0.5 }),
+    ///     LinearColor::new(0., 0., 0.),
     /// );
     /// ```
     pub fn new(
         diffuse: LinearColor,
         specular: LinearColor,
         refl_trans: Option<ReflTransEnum>,
+        emitted: LinearColor,
     ) -> Self {
         LightProperties {
             diffuse,
             specular,
             refl_trans,
+            emitted,
         }
     }
 }
@@ -72,14 +78,20 @@ mod test {
         let diffuse = LinearColor::new(0.25, 0.5, 1.);
         let specular = LinearColor::new(0.75, 0.375, 0.125);
         let refl_trans = Some(ReflTransEnum::Reflectivity { coef: 0.5 });
-        let properties =
-            LightProperties::new(diffuse.clone(), specular.clone(), refl_trans.clone());
+        let emitted = LinearColor::new(0., 1., 0.);
+        let properties = LightProperties::new(
+            diffuse.clone(),
+            specular.clone(),
+            refl_trans.clone(),
+            emitted.clone(),
+        );
         assert_eq!(
             properties,
             LightProperties {
                 diffuse,
                 specular,
                 refl_trans,
+                emitted,
             }
         )
     }
@@ -96,7 +108,8 @@ mod test {
             LightProperties::new(
                 LinearColor::new(1., 0.5, 0.25),
                 LinearColor::new(0.25, 0.125, 0.75),
-                None
+                None,
+                LinearColor::black(),
             )
         )
     }
@@ -118,7 +131,8 @@ mod test {
                 Some(ReflTransEnum::Transparency {
                     coef: 0.5,
                     index: 1.5
-                })
+                }),
+                LinearColor::black(),
             )
         )
     }
@@ -136,7 +150,27 @@ mod test {
             LightProperties::new(
                 LinearColor::new(1., 0.5, 0.25),
                 LinearColor::new(0.25, 0.125, 0.75),
-                Some(ReflTransEnum::Reflectivity { coef: 0.25 })
+                Some(ReflTransEnum::Reflectivity { coef: 0.25 }),
+                LinearColor::black(),
+            )
+        )
+    }
+
+    #[test]
+    fn deserialization_with_emitted_works() {
+        let yaml = r#"
+            diffuse: {r: 1.0, g: 0.5, b: 0.25}
+            specular: {r: 0.25, g: 0.125, b: 0.75}
+            emitted: {r: 0.25, g: 0.5, b: 1.0}
+        "#;
+        let properties: LightProperties = serde_yaml::from_str(yaml).unwrap();
+        assert_eq!(
+            properties,
+            LightProperties::new(
+                LinearColor::new(1., 0.5, 0.25),
+                LinearColor::new(0.25, 0.125, 0.75),
+                None,
+                LinearColor::new(0.25, 0.5, 1.0),
             )
         )
     }

pathtracer/src/lib.rs

@@ -12,6 +12,7 @@ pub mod core;
 pub mod light;
 pub mod material;
 pub mod render;
+pub mod scene;
 pub mod serialize;
 pub mod shape;
 pub mod texture;

pathtracer/src/light/spot_light.rs

@@ -2,12 +2,13 @@ use super::{Light, SpatialLight};
 use crate::core::LinearColor;
 use crate::{Point, Vector};
 use nalgebra::Unit;
-use serde::{Deserialize, Deserializer};
+use serde::Deserialize;
 
 /// Represent a light emanating from a directed light-source, outputting rays in a cone.
 ///
 /// The illumination cone cannot have an FOV over 180°.
-#[derive(Debug, PartialEq)]
+#[serde(from = "SerializedSpotLight")]
+#[derive(Debug, PartialEq, Deserialize)]
 pub struct SpotLight {
     position: Point,
     direction: Unit<Vector>,
@@ -82,16 +83,6 @@ impl From<SerializedSpotLight> for SpotLight {
     }
 }
 
-impl<'de> Deserialize<'de> for SpotLight {
-    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    where
-        D: Deserializer<'de>,
-    {
-        let cam: SerializedSpotLight = Deserialize::deserialize(deserializer)?;
-        Ok(cam.into())
-    }
-}
-
 #[cfg(test)]
 mod test {
     use super::*;

pathtracer/src/main.rs

@@ -1,7 +1,19 @@
-use pathtracer::render::Scene;
+use pathtracer::render::{BidirectionalPathtracer, Pathtracer, Raytracer};
+use pathtracer::scene::Scene;
 use std::path::PathBuf;
+use std::str;
+use structopt::clap::arg_enum;
 use structopt::StructOpt;
 
+arg_enum! {
+    #[derive(Debug)]
+    enum RenderOption {
+        Raytracer,
+        Pathtracer,
+        Bidirectional,
+    }
+}
+
 #[derive(StructOpt, Debug)]
 struct Options {
     /// Input description for the scene to be rendered.
@@ -10,6 +22,15 @@ struct Options {
     /// Output image for the rendered scene.
     #[structopt(short, long, parse(from_os_str), default_value = "scene.png")]
     output: PathBuf,
+    /// Which renderer should be used on the input scene.
+    #[structopt(
+        short,
+        long,
+        possible_values = &RenderOption::variants(),
+        case_insensitive = true,
+        default_value = "Raytracer"
+    )]
+    renderer: RenderOption,
 }
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
@@ -17,7 +38,11 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let f = std::fs::File::open(options.input)?;
 
     let scene: Scene = serde_yaml::from_reader(f)?;
-    let image = scene.render();
+    let image = match options.renderer {
+        RenderOption::Raytracer => Raytracer::new(scene).render(),
+        RenderOption::Pathtracer => Pathtracer::new(scene).render(),
+        RenderOption::Bidirectional => BidirectionalPathtracer::new(scene).render(),
+    };
 
     image.save(options.output)?;
     Ok(())

pathtracer/src/material/mod.rs

@@ -9,10 +9,11 @@ use serde::Deserialize;
 #[serde(rename_all = "lowercase")]
 #[allow(missing_docs)]
 #[enum_dispatch::enum_dispatch]
-#[derive(Debug, PartialEq, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Deserialize)]
 pub enum MaterialEnum {
     #[serde(rename = "uniform")]
     UniformMaterial,
+    TriangleMaterial,
 }
 
 /// Represent the physical light properties of an object in the scene;
@@ -22,5 +23,8 @@ pub trait Material: std::fmt::Debug {
     fn properties(&self, point: Point2D) -> LightProperties;
 }
 
+mod triangle;
+pub use triangle::*;
+
 mod uniform;
 pub use uniform::*;

pathtracer/src/material/triangle.rs

@@ -0,0 +1,33 @@
+use super::Material;
+use crate::core::{LightProperties, LinearColor, ReflTransEnum};
+use crate::Point2D;
+use serde::Deserialize;
+
+/// Represent a material which interpolates between three points.
+#[derive(Debug, Clone, PartialEq, Deserialize)]
+pub struct TriangleMaterial {
+    /// The diffuse components.
+    diffuse: [LinearColor; 3],
+    /// The specular components.
+    specular: [LinearColor; 3],
+    /// The transparency or reflectivity properties, this is not interpolated.
+    #[serde(flatten)]
+    refl_trans: Option<ReflTransEnum>,
+    /// The amount of light emitted by the material, only used during path-tracing rendering.
+    emitted: [LinearColor; 3],
+}
+
+impl Material for TriangleMaterial {
+    fn properties(&self, point: Point2D) -> LightProperties {
+        let (u, v) = (point.x, point.y);
+        let sample = |param: &[LinearColor; 3]| -> LinearColor {
+            param[0].clone() * (1. - u - v) + param[1].clone() * u + param[2].clone() * v
+        };
+        let diffuse = sample(&self.diffuse);
+        let specular = sample(&self.specular);
+        let emitted = sample(&self.emitted);
+        LightProperties::new(diffuse, specular, self.refl_trans.clone(), emitted)
+    }
+}
+
+// FIXME: tests

pathtracer/src/material/uniform.rs

@@ -24,6 +24,7 @@ impl UniformMaterial {
     ///         LinearColor::new(1.0, 0.0, 0.0), // diffuse component
     ///         LinearColor::new(0.0, 0.0, 0.0), // specular component
     ///         None,
+    ///         LinearColor::black(), // Emitted light
     ///     ),
     /// );
     /// ```
@@ -50,6 +51,7 @@ mod test {
             diffuse: LinearColor::new(0., 0.5, 0.),
             specular: LinearColor::new(1., 1., 1.),
             refl_trans: None,
+            emitted: LinearColor::black(),
         };
         let mat = UniformMaterial::new(properties.clone());
         assert_eq!(mat, UniformMaterial { properties })
@@ -61,6 +63,7 @@ mod test {
             LinearColor::new(0., 0.5, 0.),
             LinearColor::new(1., 1., 1.),
             None,
+            LinearColor::black(),
         );
         let mat = UniformMaterial::new(properties.clone());
         assert_eq!(mat.properties(Point2D::origin()), properties)
@@ -79,7 +82,8 @@ mod test {
             UniformMaterial::new(LightProperties::new(
                 LinearColor::new(1., 0.5, 0.25),
                 LinearColor::new(0.25, 0.125, 0.75),
-                Some(ReflTransEnum::Reflectivity { coef: 0.25 })
+                Some(ReflTransEnum::Reflectivity { coef: 0.25 }),
+                LinearColor::black(),
             ))
         )
     }

pathtracer/src/render/bidirectional/bidirectional_pathtracer.rs

@@ -0,0 +1,50 @@
+use super::super::Renderer;
+use super::path::*;
+use crate::scene::Scene;
+use crate::{Point, Vector};
+use image::RgbImage;
+use nalgebra::Unit;
+
+/// Render the [`Scene`] using Bidirectional-Pathtracing
+///
+/// [`Scene`]: ../scene/scene/struct.Scene.html
+pub struct BidirectionalPathtracer {
+    #[allow(unused)]
+    scene: Scene,
+}
+
+impl BidirectionalPathtracer {
+    /// Create a [`BidirectionalPathtracer`] renderer with the given [`Scene`]
+    ///
+    /// [`BidirectionalPathtracer`]: struct.BidirectionalPathtracer.html
+    /// [`Scene`]: ../scene/scene/struct.Scene.html
+    pub fn new(scene: Scene) -> Self {
+        BidirectionalPathtracer { scene }
+    }
+
+    /// Render the [`Scene`] using Bidirectional-Pathtracing.
+    ///
+    /// [`Scene`]: ../scene/scene/struct.Scene.html
+    pub fn render(&self) -> RgbImage {
+        todo!()
+    }
+
+    #[allow(unused)]
+    fn construct_path(&self, point: Point, _direction: Unit<Vector>) -> Path {
+        let mut res = Path::new(point);
+        for _ in 0..self.scene.reflection_limit {
+            // FIXME:
+            //  * cast_ray: if no intersection, return the empty path
+            //  * look-up information at intersection
+            //  * append to path
+            //  * start again with new origin
+        }
+        res
+    }
+}
+
+impl Renderer for BidirectionalPathtracer {
+    fn render(&self) -> RgbImage {
+        self.render()
+    }
+}

pathtracer/src/render/bidirectional/mod.rs

@@ -0,0 +1,4 @@
+mod path;
+
+mod bidirectional_pathtracer;
+pub use bidirectional_pathtracer::*;

pathtracer/src/render/bidirectional/path.rs

@@ -0,0 +1,47 @@
+use crate::core::LightProperties;
+use crate::{Point, Vector};
+use nalgebra::Unit;
+
+pub struct PathPoint {
+    pub point: Point,
+    pub incident: Unit<Vector>,
+    pub normal: Unit<Vector>,
+    pub properties: LightProperties,
+}
+
+impl PathPoint {
+    #[allow(unused)]
+    pub fn new(
+        point: Point,
+        incident: Unit<Vector>,
+        normal: Unit<Vector>,
+        properties: LightProperties,
+    ) -> Self {
+        PathPoint {
+            point,
+            incident,
+            normal,
+            properties,
+        }
+    }
+}
+
+pub struct Path {
+    pub origin: Point,
+    pub points: Vec<PathPoint>,
+}
+
+impl Path {
+    #[allow(unused)]
+    pub fn new(origin: Point) -> Self {
+        Path {
+            origin,
+            points: Vec::new(),
+        }
+    }
+
+    #[allow(unused)]
+    pub fn push_point(&mut self, new_point: PathPoint) {
+        self.points.push(new_point)
+    }
+}

pathtracer/src/render/mod.rs

@@ -1,12 +1,22 @@
-//! Rendering logic
+//! Define the different kinds of renderers for use on a given scene.
+use image::RgbImage;
 
-pub mod light_aggregate;
-pub use light_aggregate::*;
+/// Each renderer implements this trait, to be called after being built.
+pub trait Renderer {
+    /// Render the [`Scene`] using the chosen rendering technique.
+    ///
+    /// [`Scene`]: ../scene/scene/struct.Scene.html
+    fn render(&self) -> RgbImage;
+}
 
-pub mod object;
-pub use object::*;
+mod bidirectional;
+pub use bidirectional::*;
 
-pub mod scene;
-pub use scene::*;
+mod pathtrace;
+pub use pathtrace::*;
 
+mod raytrace;
+pub use raytrace::*;
+
+pub(crate) mod progress;
 pub(crate) mod utils;

pathtracer/src/render/pathtrace/mod.rs

@@ -0,0 +1,2 @@
+mod pathtracer;
+pub use self::pathtracer::*;

pathtracer/src/render/pathtrace/pathtracer.rs

@@ -0,0 +1,135 @@
+use indicatif::ProgressIterator;
+use rayon::prelude::*;
+
+use super::super::utils::{buffer_to_image, sample_hemisphere};
+use super::super::Renderer;
+use crate::{
+    core::LinearColor,
+    material::Material,
+    scene::{Object, Scene},
+    shape::Shape,
+};
+use beevee::ray::Ray;
+use image::RgbImage;
+
+/// Render the [`Scene`] using Pathtracing
+///
+/// [`Scene`]: ../scene/scene/struct.Scene.html
+pub struct Pathtracer {
+    #[allow(unused)]
+    scene: Scene,
+}
+
+impl Pathtracer {
+    /// Create a [`Pathtracer`] renderer with the given [`Scene`]
+    ///
+    /// [`Pathtracer`]: struct.Pathtracer.html
+    /// [`Scene`]: ../scene/scene/struct.Scene.html
+    pub fn new(scene: Scene) -> Self {
+        Pathtracer { scene }
+    }
+
+    /// Render the [`Scene`] using Pathtracing.
+    ///
+    /// [`Scene`]: ../scene/scene/struct.Scene.html
+    pub fn render(&self) -> RgbImage {
+        let (width, height) = (
+            self.scene.camera.film().width(),
+            self.scene.camera.film().height(),
+        );
+        let total = width * height;
+
+        let p = super::super::progress::get_passes_progressbar(self.scene.shot_rays);
+
+        // Ensure at least one round of shots
+        let (img_buf, _) = (0..self.scene.shot_rays.max(1))
+            .progress_with(p)
+            .map(|_| {
+                let mut buffer: Vec<LinearColor> = Vec::new();
+                buffer.resize_with(total as usize, LinearColor::black);
+
+                buffer
+                    .par_chunks_mut(width as usize)
+                    .enumerate()
+                    .for_each(|(y, row)| {
+                        for x in 0..width {
+                            row[x as usize] += self.pixel_ray(x as f32, y as f32);
+                        }
+                    });
+
+                buffer
+            })
+            .fold(
+                {
+                    let mut vec = Vec::new();
+                    vec.resize_with(total as usize, LinearColor::black);
+                    let count = 0usize;
+                    (vec, count)
+                },
+                |(mut acc, count), buf| {
+                    for (i, pixel) in buf.into_iter().enumerate() {
+                        acc[i] += pixel;
+                    }
+
+                    let count = count + 1; // Because count is 0-indexed
+                    if self.scene.steps.contains(&count) {
+                        let image = buffer_to_image(&acc, count as u32, width, height);
+                        image
+                            .save(format!("{}_passes.png", count))
+                            .expect("writing image failed!");
+                    }
+
+                    (acc, count) // Count has been updated previously
+                },
+            );
+
+        buffer_to_image(&img_buf, self.scene.shot_rays, width, height)
+    }
+
+    fn pixel_ray(&self, x: f32, y: f32) -> LinearColor {
+        let (x, y) = self.scene.camera.film().pixel_ratio(x, y);
+        let ray = self.scene.camera.ray_with_ratio(x, y);
+        self.cast_ray(ray).map_or_else(
+            || self.scene.background.clone(),
+            |(t, obj)| self.radiance(ray, t, obj, self.scene.reflection_limit),
+        )
+    }
+
+    fn radiance(&self, ray: Ray, t: f32, obj: &Object, limit: u32) -> LinearColor {
+        // This doesn't look great, but it works ¯\_(ツ)_/¯
+
+        let hit_pos = ray.origin + ray.direction.as_ref() * t;
+        let texel = obj.shape.project_texel(&hit_pos);
+        let properties = obj.material.properties(texel);
+        // If we are the at recursion limit, return the light emitted by the object
+        if limit == 0 {
+            return properties.emitted;
+        };
+        // Get BRDF
+        // FIXME: what about the material's albedo ?
+        let brdf = properties.diffuse;
+        // Pick a new direction
+        let normal = obj.shape.normal(&hit_pos);
+        let (new_direction, weight) = sample_hemisphere(normal);
+        let cos_new_ray = new_direction.dot(&normal);
+        // Calculate the incoming light along the new ray
+        let new_ray = Ray::new(hit_pos + new_direction.as_ref() * 0.001, new_direction);
+        let incoming = self
+            .cast_ray(new_ray)
+            .map_or_else(LinearColor::black, |(t, obj)| {
+                self.radiance(new_ray, t, obj, limit - 1)
+            });
+        // Put it all together
+        properties.emitted + (brdf * incoming * cos_new_ray * weight)
+    }
+
+    fn cast_ray(&self, ray: Ray) -> Option<(f32, &Object)> {
+        self.scene.bvh.walk(&ray, &self.scene.objects)
+    }
+}
+
+impl Renderer for Pathtracer {
+    fn render(&self) -> RgbImage {
+        self.render()
+    }
+}

pathtracer/src/render/progress.rs

@@ -0,0 +1,26 @@
+use indicatif::{ProgressBar, ProgressStyle};
+
+pub fn get_progressbar(total: u64, style: &str) -> ProgressBar {
+    let pb = ProgressBar::new(total);
+    pb.set_draw_delta((total / 10000).max(1));
+    pb.set_style(ProgressStyle::default_bar().template(style));
+    pb
+}
+
+pub fn get_pixels_progressbar(total: u64) -> ProgressBar {
+    get_progressbar(
+        total,
+        "{spinner:.green} [{elapsed_precise}] [{wide_bar:.cyan/blue}] {percent:>3}%: {pos}/{len} pixels (ETA: {eta})",
+    )
+}
+
+pub fn get_passes_progressbar(total: u32) -> ProgressBar {
+    let pb = get_progressbar(
+        total as u64,
+        "{spinner:.green} [{elapsed_precise}] [{wide_bar:.cyan/blue}] {percent:>3}%: {pos}/{len} passes (ETA: {eta})",
+    );
+
+    pb.enable_steady_tick(1000);
+
+    pb
+}

pathtracer/src/render/raytrace/mod.rs

@@ -0,0 +1,2 @@
+mod raytracer;
+pub use self::raytracer::*;

pathtracer/src/render/raytrace/raytracer.rs

@@ -1,102 +1,48 @@
-//! Scene rendering logic
-
-use super::{light_aggregate::LightAggregate, object::Object, utils::*};
+use super::super::utils::*;
+use super::super::Renderer;
+use crate::scene::{Object, Scene};
 use crate::{
-    core::{Camera, LightProperties, LinearColor, ReflTransEnum},
+    core::{LightProperties, LinearColor, ReflTransEnum},
     material::Material,
     shape::Shape,
     texture::Texture,
     {Point, Vector},
 };
-use beevee::{bvh::BVH, ray::Ray};
+use beevee::ray::Ray;
 use image::RgbImage;
 use nalgebra::Unit;
 use rand::prelude::thread_rng;
 use rand::Rng;
-use serde::{Deserialize, Deserializer};
 
-/// Represent the scene being rendered.
-pub struct Scene {
-    camera: Camera,
-    lights: LightAggregate,
-    objects: Vec<Object>,
-    bvh: BVH,
-    background: LinearColor,
-    aliasing_limit: u32,
-    reflection_limit: u32,
-    diffraction_index: f32,
-}
-
-impl Scene {
-    /// Creates a new `Scene`.
+/// Render the [`Scene`] using Raytracing.
 ///
-    /// # Examples
-    ///
-    /// ```
-    /// # use pathtracer::core::{Camera, LightProperties, LinearColor};
-    /// # use pathtracer::material::UniformMaterial;
-    /// # use pathtracer::render::{LightAggregate, Object, Scene};
-    /// # use pathtracer::shape::Sphere;
-    /// # use pathtracer::texture::UniformTexture;
-    /// # use pathtracer::Point;
-    /// #
-    /// let scene = Scene::new(
-    ///     Camera::default(),
-    ///     LightAggregate::empty(),
-    ///     vec![
-    ///         Object::new(
-    ///             Sphere::new(Point::origin(), 1.0).into(),
-    ///             UniformMaterial::new(
-    ///                 LightProperties::new(
-    ///                     LinearColor::new(1.0, 0.0, 0.0), // diffuse component
-    ///                     LinearColor::new(0.0, 0.0, 0.0), // specular component
-    ///                     None,
-    ///                 ),
-    ///             ).into(),
-    ///             UniformTexture::new(LinearColor::new(0.5, 0.5, 0.5)).into(),
-    ///         ),
-    ///     ],
-    ///     LinearColor::black(), // Background color
-    ///     5,   // aliasing limit
-    ///     3,   // reflection recursion limit
-    ///     0.0, // diffraction index
-    /// );
-    /// ```
-    pub fn new(
-        camera: Camera,
-        lights: LightAggregate,
-        mut objects: Vec<Object>,
-        background: LinearColor,
-        aliasing_limit: u32,
-        reflection_limit: u32,
-        diffraction_index: f32,
-    ) -> Self {
-        // NOTE(Antoine): fun fact: BVH::build stack overflows when given an empty slice :)
-        let bvh = BVH::build(&mut objects);
-        Scene {
-            camera,
-            lights,
-            objects,
-            bvh,
-            background,
-            aliasing_limit,
-            reflection_limit,
-            diffraction_index,
-        }
+/// [`Scene`]: ../scene/scene/struct.Scene.html
+pub struct Raytracer {
+    scene: Scene,
 }
 
-    /// Render the scene into an image.
+impl Raytracer {
+    /// Create a [`Raytracer`] renderer with the given [`Scene`]
+    ///
+    /// [`Raytracer`]: struct.Raytracer.html
+    /// [`Scene`]: ../scene/scene/struct.Scene.html
+    pub fn new(scene: Scene) -> Self {
+        Raytracer { scene }
+    }
+
+    /// Render the [`Scene`] using Raytracing.
+    ///
+    /// [`Scene`]: ../scene/scene/struct.Scene.html
     pub fn render(&self) -> RgbImage {
-        let mut image = RgbImage::new(self.camera.film().width(), self.camera.film().height());
+        let mut image = RgbImage::new(
+            self.scene.camera.film().width(),
+            self.scene.camera.film().height(),
+        );
 
         let total = (image.width() * image.height()) as u64;
-        let pb = indicatif::ProgressBar::new(total);
-        pb.set_draw_delta(total / 10000);
-        pb.set_style(indicatif::ProgressStyle::default_bar().template(
-            "{spinner:.green} [{elapsed_precise}] [{wide_bar:.cyan/blue}] {percent:>3}%: {pos}/{len} pixels (ETA: {eta})",
-        ));
+        let pb = super::super::progress::get_pixels_progressbar(total);
 
-        let pixel_func = if self.aliasing_limit > 0 {
+        let pixel_func = if self.scene.shot_rays > 0 {
             Self::anti_alias_pixel
         } else {
             Self::pixel
@@ -121,18 +67,17 @@ impl Scene {
 
     /// Get pixel color for (x, y) a pixel **coordinate**
     fn pixel(&self, x: f32, y: f32) -> LinearColor {
-        let (x, y) = self.camera.film().pixel_ratio(x, y);
-        let pixel = self.camera.film().pixel_at_ratio(x, y);
-        let direction = Unit::new_normalize(pixel - self.camera.origin());
-        let indices = RefractionInfo::with_index(self.diffraction_index);
-        self.cast_ray(Ray::new(pixel, direction)).map_or_else(
-            || self.background.clone(),
+        let (x, y) = self.scene.camera.film().pixel_ratio(x, y);
+        let indices = RefractionInfo::with_index(self.scene.diffraction_index);
+        let ray = self.scene.camera.ray_with_ratio(x, y);
+        self.cast_ray(ray).map_or_else(
+            || self.scene.background.clone(),
             |(t, obj)| {
                 self.color_at(
-                    pixel + direction.as_ref() * t,
+                    ray.origin + ray.direction.as_ref() * t,
                     obj,
-                    direction,
-                    self.reflection_limit,
+                    ray.direction,
+                    self.scene.reflection_limit,
                     indices,
                 )
             },
@@ -141,7 +86,7 @@ impl Scene {
 
     /// Get pixel color with anti-aliasing
     fn anti_alias_pixel(&self, x: f32, y: f32) -> LinearColor {
-        let range = 0..self.aliasing_limit;
+        let range = 0..self.scene.shot_rays;
         let mut rng = thread_rng();
         let acc: LinearColor = range
             .map(|_| {
@@ -151,11 +96,11 @@ impl Scene {
             })
             .map(LinearColor::clamp)
             .sum();
-        acc / self.aliasing_limit as f32
+        acc / self.scene.shot_rays as f32
     }
 
     fn cast_ray(&self, ray: Ray) -> Option<(f32, &Object)> {
-        self.bvh.walk(&ray, &self.objects)
+        self.scene.bvh.walk(&ray, &self.scene.objects)
     }
 
     fn color_at(
@@ -173,6 +118,9 @@ impl Scene {
         let normal = object.shape.normal(&point);
         let reflected_ray = reflected(incident_ray, normal);
 
+        // FIXME: change this to averaged sampled rays instead of visiting every light ?
+        // Indeed the path-tracing algorithm is good for calculating the radiance at a point
+        // But it should be used for reflection and refraction too...
         let lighting = self.illuminate(point, object_color, &properties, normal, reflected_ray);
         if properties.refl_trans.is_none() {
             // Avoid calculating reflection when not needed
@@ -261,7 +209,8 @@ impl Scene {
     }
 
     fn illuminate_ambient(&self, color: LinearColor) -> LinearColor {
-        self.lights
+        self.scene
+            .lights
             .ambient_lights_iter()
             .map(|light| color.clone() * light.illumination(&Point::origin()))
             .map(LinearColor::clamp)
@@ -275,11 +224,12 @@ impl Scene {
         normal: Unit<Vector>,
         reflected: Unit<Vector>,
     ) -> LinearColor {
-        self.lights
+        self.scene
+            .lights
             .spatial_lights_iter()
             .map(|light| {
                 let (direction, t) = light.to_source(&point);
-                let light_ray = Ray::new(point + 0.001 * direction.as_ref(), direction);
+                let light_ray = Ray::new(point + direction.as_ref() * 0.001, direction);
                 match self.cast_ray(light_ray) {
                     // Take shadows into account
                     Some((obstacle_t, _)) if obstacle_t < t => return LinearColor::black(),
@@ -295,72 +245,8 @@ impl Scene {
     }
 }
 
-#[derive(Debug, PartialEq, Deserialize)]
-struct SerializedScene {
-    camera: Camera,
-    #[serde(default)]
-    lights: LightAggregate,
-    #[serde(default)]
-    objects: Vec<Object>,
-    #[serde(default)]
-    background: LinearColor,
-    #[serde(default)]
-    aliasing_limit: u32,
-    #[serde(default)]
-    reflection_limit: u32,
-    #[serde(default = "crate::serialize::default_identity")]
-    starting_diffraction: f32,
-}
-
-impl From<SerializedScene> for Scene {
-    fn from(scene: SerializedScene) -> Self {
-        Scene::new(
-            scene.camera,
-            scene.lights,
-            scene.objects,
-            scene.background,
-            scene.aliasing_limit,
-            scene.reflection_limit,
-            scene.starting_diffraction,
-        )
-    }
-}
-
-impl<'de> Deserialize<'de> for Scene {
-    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    where
-        D: Deserializer<'de>,
-    {
-        let cam: SerializedScene = Deserialize::deserialize(deserializer)?;
-        Ok(cam.into())
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-
-    #[test]
-    fn deserialization_works() {
-        let yaml = std::include_str!("../../examples/scene.yaml");
-        let _: Scene = serde_yaml::from_str(yaml).unwrap();
-        // FIXME: actually test the equality ?
-    }
-
-    #[test]
-    #[ignore] // stack overflow because of BVH :(
-    fn bvh_fails() {
-        use crate::core::Camera;
-        use crate::render::{LightAggregate, Scene};
-
-        let _scene = Scene::new(
-            Camera::default(),
-            LightAggregate::empty(),
-            Vec::new(),           // Objects list
-            LinearColor::black(), // Background color
-            5,                    // aliasing limit
-            3,                    // reflection recursion limit
-            0.0,                  // diffraction index
-        );
+impl Renderer for Raytracer {
+    fn render(&self) -> RgbImage {
+        self.render()
     }
 }

pathtracer/src/render/utils.rs

@@ -1,5 +1,9 @@
+use crate::core::LinearColor;
 use crate::Vector;
+use image::RgbImage;
 use nalgebra::Unit;
+use rand::prelude::thread_rng;
+use rand::Rng;
 
 pub fn reflected(incident: Unit<Vector>, normal: Unit<Vector>) -> Unit<Vector> {
     let proj = incident.dot(&normal);
@@ -65,3 +69,68 @@ impl RefractionInfo {
         std::mem::swap(&mut self.old_index, &mut self.new_index)
     }
 }
+
+/// Returns a random ray in the hemisphere described by a normal unit-vector, and the probability
+/// to have picked that direction.
+pub fn sample_hemisphere(normal: Unit<Vector>) -> (Unit<Vector>, f32) {
+    let mut rng = thread_rng();
+    let azimuth = rng.gen::<f32>() * std::f32::consts::PI * 2.;
+    // Cosine weighted importance sampling
+    let cos_elevation: f32 = rng.gen();
+    let sin_elevation = f32::sqrt(1. - cos_elevation * cos_elevation);
+
+    let x = sin_elevation * azimuth.cos();
+    let y = cos_elevation;
+    let z = sin_elevation * azimuth.sin();
+
+    // Calculate orthonormal base, defined by (normalb_b, normal, normal_t)
+    // Pay attention to degenerate cases when (y, z) is small for use with cross product
+    let normal_t = if normal.x.abs() > normal.y.abs() {
+        Vector::new(normal.z, 0., -normal.x).normalize()
+    } else {
+        Vector::new(0., -normal.z, normal.y).normalize()
+    };
+    let normal_b = normal.cross(&normal_t);
+
+    // Perform the matrix calculation by hand...
+    let scattered = Unit::new_normalize(Vector::new(
+        x * normal_b.x + y * normal.x + z * normal_t.x,
+        x * normal_b.y + y * normal.y + z * normal_t.y,
+        x * normal_b.z + y * normal.z + z * normal_t.z,
+    ));
+
+    // The probability to have picked the ray is inversely proportional to cosine of the angle with
+    // the normal
+    (scattered, (1. / scattered.dot(&normal)).min(f32::MAX))
+}
+
+pub fn buffer_to_image(buffer: &[LinearColor], passes: u32, width: u32, height: u32) -> RgbImage {
+    let mut image = RgbImage::new(width, height);
+
+    for (x, y, pixel) in image.enumerate_pixels_mut() {
+        let i = x as usize + y as usize * width as usize;
+        *pixel = (buffer[i].clone() / passes as f32).into();
+    }
+
+    image
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn sample_hemisphere_work() {
+        // NOTE(Bruno): should use some test-case generation for failure-reproduction purposes...
+        let mut rng = thread_rng();
+        for _ in 0..100 {
+            let normal = Unit::new_normalize(Vector::new(rng.gen(), rng.gen(), rng.gen()));
+            for _ in 0..100 {
+                let (sample, proportion) = sample_hemisphere(normal);
+                let cos_angle = normal.dot(&sample);
+                assert!(cos_angle >= 0.);
+                assert!(1. / cos_angle - proportion < std::f32::EPSILON);
+            }
+        }
+    }
+}

pathtracer/src/scene/light_aggregate.rs

@@ -23,7 +23,7 @@ impl LightAggregate {
     /// # Examples
     ///
     /// ```
-    /// # use pathtracer::render::LightAggregate;
+    /// # use pathtracer::scene::LightAggregate;
     /// #
     /// let la = LightAggregate::empty();
     /// assert_eq!(la.ambient_lights_iter().count(), 0);
@@ -40,7 +40,7 @@ impl LightAggregate {
     /// # Examples
     ///
     /// ```
-    /// # use pathtracer::render::LightAggregate;
+    /// # use pathtracer::scene::LightAggregate;
     /// #
     /// let la = LightAggregate::new(
     ///     Vec::new(),

pathtracer/src/scene/mesh.rs

@@ -0,0 +1,182 @@
+use std::convert::TryFrom;
+use std::path::PathBuf;
+
+use nalgebra::{Similarity3, Unit, VectorSlice3};
+
+use serde::Deserialize;
+
+use tobj::{self, load_obj};
+
+use super::Object;
+use crate::{
+    core::{LightProperties, LinearColor},
+    material::{MaterialEnum, UniformMaterial},
+    shape::{InterpolatedTriangle, ShapeEnum, Triangle},
+    texture::{TextureEnum, UniformTexture},
+    Point, Vector,
+};
+
+/// Represent a mesh of objects.
+#[serde(try_from = "Wavefront")]
+#[derive(Debug, PartialEq, Deserialize)]
+pub struct Mesh {
+    /// The shapes composing the mesh
+    pub(crate) shapes: Vec<Object>,
+}
+
+#[derive(Debug, PartialEq, Deserialize)]
+pub(crate) struct Wavefront {
+    pub obj_file: PathBuf,
+    #[serde(default = "nalgebra::zero")]
+    translation: Vector,
+    #[serde(default = "nalgebra::zero")]
+    rotation: Vector,
+    #[serde(default = "crate::serialize::coefficient::default_identity")]
+    scale: f32,
+}
+
+fn parse_float3(s: &str) -> Result<[f32; 3], tobj::LoadError> {
+    let mut res = [0.0, 0.0, 0.0];
+    let mut count = 0;
+
+    for (i, s) in s.split_whitespace().enumerate() {
+        if count == 3 {
+            return Err(tobj::LoadError::MaterialParseError);
+        }
+
+        res[i] = s.parse().map_err(|_| tobj::LoadError::MaterialParseError)?;
+        count += 1;
+    }
+
+    if count < 3 {
+        return Err(tobj::LoadError::MaterialParseError);
+    }
+
+    Ok(res)
+}
+
+impl TryFrom<Wavefront> for Mesh {
+    type Error = tobj::LoadError;
+
+    fn try_from(wavefront: Wavefront) -> Result<Mesh, Self::Error> {
+        let mut shapes = Vec::new();
+
+        let (models, materials) = load_obj(&wavefront.obj_file)?;
+
+        // The object to world transformation matrix
+        let transform = Similarity3::new(
+            wavefront.translation,
+            wavefront.rotation * std::f32::consts::PI / 180., // From degrees to radians
+            wavefront.scale,
+        );
+
+        for model in models {
+            let mesh = &model.mesh;
+
+            // mesh.indices contains all vertices. Each group of 3 vertices
+            // is a triangle, so we iterate over indices 3 by 3.
+            for i in 0..(mesh.indices.len() / 3) {
+                let (a, b, c) = (
+                    mesh.indices[i * 3] as usize,
+                    mesh.indices[i * 3 + 1] as usize,
+                    mesh.indices[i * 3 + 2] as usize,
+                );
+
+                let pos_a = transform * Point::from_slice(&mesh.positions[(a * 3)..(a * 3 + 3)]);
+                let pos_b = transform * Point::from_slice(&mesh.positions[(b * 3)..(b * 3 + 3)]);
+                let pos_c = transform * Point::from_slice(&mesh.positions[(c * 3)..(c * 3 + 3)]);
+
+                let triangle: ShapeEnum = if mesh.normals.is_empty() {
+                    Triangle::new(pos_a, pos_b, pos_c).into()
+                } else {
+                    // We apply the (arguably useless) scaling to the vectors in case it is
+                    // negative, which would invert their direction
+                    let norm_a = {
+                        let vec: Vector =
+                            VectorSlice3::from_slice(&mesh.normals[(a * 3)..(a * 3 + 3)]).into();
+                        Unit::new_normalize(transform * vec)
+                    };
+                    let norm_b = {
+                        let vec: Vector =
+                            VectorSlice3::from_slice(&mesh.normals[(b * 3)..(b * 3 + 3)]).into();
+                        Unit::new_normalize(transform * vec)
+                    };
+                    let norm_c = {
+                        let vec: Vector =
+                            VectorSlice3::from_slice(&mesh.normals[(c * 3)..(c * 3 + 3)]).into();
+                        Unit::new_normalize(transform * vec)
+                    };
+
+                    InterpolatedTriangle::new(pos_a, pos_b, pos_c, norm_a, norm_b, norm_c).into()
+                };
+
+                // FIXME: handle material
+                let (material, texture): (MaterialEnum, TextureEnum) =
+                    if let Some(mat_id) = mesh.material_id {
+                        let mesh_mat = &materials[mat_id];
+
+                        let diffuse = LinearColor::from_slice(&mesh_mat.ambient[..]);
+                        let specular = LinearColor::from_slice(&mesh_mat.ambient[..]);
+                        let emitted = mesh_mat
+                            .unknown_param
+                            .get("Ke")
+                            // we want a default if "Ke" isn't provided, but we
+                            // want an error if it is provided but its value
+                            // doesn't parse
+                            .map_or(Ok(LinearColor::black()), |ke| {
+                                parse_float3(ke).map(|vals| LinearColor::from_slice(&vals))
+                            })?;
+
+                        let material = UniformMaterial::new(LightProperties::new(
+                            diffuse.clone(),
+                            specular,
+                            // FIXME: material.dissolve is supposed to be "the alpha term"
+                            // Needs translation to our ReflTransEnum
+                            None,
+                            emitted,
+                        ));
+
+                        // we only handle uniform textures
+                        let texture = UniformTexture::new(diffuse);
+
+                        (material.into(), texture.into())
+                    } else {
+                        // FIXME: should we accept this, and use a default
+                        // Material, or throw a LoadError
+                        (
+                            UniformMaterial::new(LightProperties::new(
+                                LinearColor::new(0.5, 0.5, 0.5),
+                                LinearColor::new(0.1, 0.1, 0.1),
+                                None,
+                                LinearColor::black(),
+                            ))
+                            .into(),
+                            UniformTexture::new(LinearColor::new(0.5, 0.5, 0.5)).into(),
+                        )
+                    };
+
+                shapes.push(Object::new(triangle, material, texture));
+            }
+        }
+
+        Ok(Mesh { shapes })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_float3_works() {
+        assert_eq!(parse_float3("1 1 1"), Ok([1., 1., 1.]));
+        assert_eq!(
+            parse_float3("1 1"),
+            Err(tobj::LoadError::MaterialParseError)
+        );
+        assert_eq!(
+            parse_float3("1 1 1 1"),
+            Err(tobj::LoadError::MaterialParseError)
+        );
+    }
+}

pathtracer/src/scene/mod.rs

@@ -0,0 +1,167 @@
+//! Desciption of the scene.
+
+use beevee::bvh::BVH;
+use serde::Deserialize;
+
+use crate::core::{Camera, LinearColor};
+
+pub mod light_aggregate;
+pub use light_aggregate::*;
+
+mod mesh;
+pub use mesh::*;
+
+pub mod object;
+pub use object::*;
+
+/// Represent the scene being rendered.
+#[serde(from = "SerializedScene")]
+#[derive(Debug, PartialEq, Deserialize)]
+pub struct Scene {
+    pub(crate) camera: Camera,
+    pub(crate) lights: LightAggregate,
+    pub(crate) objects: Vec<Object>,
+    pub(crate) bvh: BVH,
+    pub(crate) background: LinearColor,
+    pub(crate) shot_rays: u32,
+    pub(crate) reflection_limit: u32,
+    pub(crate) diffraction_index: f32,
+    pub(crate) steps: Vec<usize>,
+}
+
+impl Scene {
+    #[allow(clippy::too_many_arguments)]
+    /// Creates a new `Scene`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use pathtracer::core::{Camera, LightProperties, LinearColor};
+    /// # use pathtracer::material::UniformMaterial;
+    /// # use pathtracer::scene::{LightAggregate, Object, Scene};
+    /// # use pathtracer::shape::Sphere;
+    /// # use pathtracer::texture::UniformTexture;
+    /// # use pathtracer::Point;
+    /// #
+    /// let scene = Scene::new(
+    ///     Camera::default(),
+    ///     LightAggregate::empty(),
+    ///     vec![
+    ///         Object::new(
+    ///             Sphere::new(Point::origin(), 1.0).into(),
+    ///             UniformMaterial::new(
+    ///                 LightProperties::new(
+    ///                     LinearColor::new(1.0, 0.0, 0.0), // diffuse component
+    ///                     LinearColor::new(0.0, 0.0, 0.0), // specular component
+    ///                     None,
+    ///                     LinearColor::black(), // Emitted light
+    ///                 ),
+    ///             ).into(),
+    ///             UniformTexture::new(LinearColor::new(0.5, 0.5, 0.5)).into(),
+    ///         ),
+    ///     ],
+    ///     LinearColor::black(), // Background color
+    ///     5,   // amount of rays shot per pixel
+    ///     3,   // reflection recursion limit
+    ///     0.0, // diffraction index
+    ///     Vec::new(), // steps
+    /// );
+    /// ```
+    pub fn new(
+        camera: Camera,
+        lights: LightAggregate,
+        mut objects: Vec<Object>,
+        background: LinearColor,
+        shot_rays: u32,
+        reflection_limit: u32,
+        diffraction_index: f32,
+        steps: Vec<usize>,
+    ) -> Self {
+        let bvh = BVH::build(&mut objects);
+        Scene {
+            camera,
+            lights,
+            objects,
+            bvh,
+            background,
+            shot_rays,
+            reflection_limit,
+            diffraction_index,
+            steps,
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Deserialize)]
+#[serde(deny_unknown_fields)]
+struct SerializedScene {
+    camera: Camera,
+    #[serde(default)]
+    lights: LightAggregate,
+    #[serde(default)]
+    objects: Vec<Object>,
+    #[serde(default)]
+    meshes: Vec<Mesh>,
+    #[serde(default)]
+    background: LinearColor,
+    #[serde(default)]
+    shot_rays: u32,
+    #[serde(default)]
+    reflection_limit: u32,
+    #[serde(default = "crate::serialize::default_identity")]
+    starting_diffraction: f32,
+    #[serde(default)]
+    steps: Vec<usize>,
+}
+
+impl From<SerializedScene> for Scene {
+    fn from(mut scene: SerializedScene) -> Self {
+        let mut flattened_meshes: Vec<Object> = scene
+            .meshes
+            .into_iter()
+            .map(|m| m.shapes)
+            .flatten()
+            .collect();
+        scene.objects.append(&mut flattened_meshes);
+
+        Scene::new(
+            scene.camera,
+            scene.lights,
+            scene.objects,
+            scene.background,
+            scene.shot_rays,
+            scene.reflection_limit,
+            scene.starting_diffraction,
+            scene.steps,
+        )
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn deserialization_works() {
+        let yaml = std::include_str!("../../examples/scene.yaml");
+        let _: Scene = serde_yaml::from_str(yaml).unwrap();
+        // FIXME: actually test the equality ?
+    }
+
+    #[test]
+    fn empty_scene() {
+        use crate::core::Camera;
+        use crate::scene::{LightAggregate, Scene};
+
+        let _scene = Scene::new(
+            Camera::default(),
+            LightAggregate::empty(),
+            Vec::new(),           // Objects list
+            LinearColor::black(), // Background color
+            5,                    // aliasing limit
+            3,                    // reflection recursion limit
+            0.0,                  // diffraction index
+            Vec::new(),           // steps
+        );
+    }
+}

pathtracer/src/scene/object.rs

@@ -1,7 +1,7 @@
 //! Logic for the scene objects
 
 use crate::material::MaterialEnum;
-use crate::shape::{Shape, ShapeEnum};
+use crate::shape::ShapeEnum;
 use crate::texture::TextureEnum;
 use crate::Point;
 use beevee::{
@@ -12,7 +12,7 @@ use beevee::{
 use serde::Deserialize;
 
 /// An object being rendered in the scene.
-#[derive(Debug, PartialEq, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Deserialize)]
 pub struct Object {
     /// The `Object`'s physical shape
     pub shape: ShapeEnum,
@@ -30,7 +30,7 @@ impl Object {
     /// ```
     /// # use pathtracer::core::{LightProperties, LinearColor};
     /// # use pathtracer::material::UniformMaterial;
-    /// # use pathtracer::render::Object;
+    /// # use pathtracer::scene::Object;
     /// # use pathtracer::shape::Sphere;
     /// # use pathtracer::texture::UniformTexture;
     /// # use pathtracer::Point;
@@ -42,6 +42,7 @@ impl Object {
     ///             LinearColor::new(1.0, 0.0, 0.0), // diffuse component
     ///             LinearColor::new(0.0, 0.0, 0.0), // specular component
     ///             None,
+    ///             LinearColor::black(), // Emitted light
     ///         ),
     ///     ).into(),
     ///     UniformTexture::new(LinearColor::new(0.5, 0.5, 0.5)).into(),
@@ -87,6 +88,7 @@ mod test {
             LinearColor::new(0.5, 0.5, 0.5),
             LinearColor::new(1., 1., 1.),
             None,
+            LinearColor::black(),
         ));
         let texture = UniformTexture::new(LinearColor::new(0.25, 0.5, 1.));
         Object::new(shape.into(), material.into(), texture.into())
@@ -99,6 +101,7 @@ mod test {
             LinearColor::new(0.5, 0.5, 0.5),
             LinearColor::new(1., 1., 1.),
             None,
+            LinearColor::black(),
         ));
         let texture = UniformTexture::new(LinearColor::new(0.25, 0.5, 1.));
         assert_eq!(

pathtracer/src/shape/interpolated_triangle.rs

@@ -0,0 +1,158 @@
+use super::triangle::Triangle;
+use super::Shape;
+use crate::{Point, Point2D, Vector};
+use beevee::aabb::{Bounded, AABB};
+use beevee::bvh::Intersected;
+use beevee::ray::Ray;
+use nalgebra::Unit;
+use serde::Deserialize;
+
+/// Represent a triangle with interpolated normals inside the scene.
+#[derive(Clone, Debug, PartialEq, Deserialize)]
+pub struct InterpolatedTriangle {
+    #[serde(flatten)]
+    tri: Triangle,
+    // FIXME: serialize with unit
+    normals: [Unit<Vector>; 3],
+}
+
+impl InterpolatedTriangle {
+    /// Creates a new `InterpolatedTriangle` from 3 [`Point`]s and 3 [`Vector`]s.
+    ///
+    /// [`Point`]: ../../type.Point.html
+    /// [`Point`]: ../../type.Vector.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use pathtracer::shape::InterpolatedTriangle;
+    /// # use pathtracer::{Point, Vector};
+    /// #
+    /// let t = InterpolatedTriangle::new(
+    ///     Point::new(1.0, 0.0, 0.0),
+    ///     Point::new(0.0, 1.0, 0.0),
+    ///     Point::new(0.0, 0.0, 1.0),
+    ///     Vector::x_axis(),
+    ///     Vector::y_axis(),
+    ///     Vector::z_axis(),
+    /// );
+    /// ```
+    pub fn new(
+        c0: Point,
+        c1: Point,
+        c2: Point,
+        n0: Unit<Vector>,
+        n1: Unit<Vector>,
+        n2: Unit<Vector>,
+    ) -> Self {
+        InterpolatedTriangle {
+            tri: Triangle::new(c0, c1, c2),
+            normals: [n0, n1, n2],
+        }
+    }
+}
+
+impl Shape for InterpolatedTriangle {
+    fn normal(&self, point: &Point) -> Unit<Vector> {
+        let (u, v) = {
+            let c = self.tri.barycentric(point);
+            (c.x, c.y)
+        };
+        let interpol = self.normals[0].as_ref() * (1. - u - v)
+            + self.normals[1].as_ref() * u
+            + self.normals[2].as_ref() * v;
+        Unit::new_normalize(interpol)
+    }
+
+    fn project_texel(&self, point: &Point) -> Point2D {
+        self.tri.project_texel(point)
+    }
+}
+
+impl Bounded for InterpolatedTriangle {
+    fn aabb(&self) -> AABB {
+        self.tri.aabb()
+    }
+
+    fn centroid(&self) -> Point {
+        self.tri.centroid()
+    }
+}
+
+impl Intersected for InterpolatedTriangle {
+    fn intersect(&self, ray: &Ray) -> Option<f32> {
+        self.tri.intersect(ray)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    fn simple_triangle() -> InterpolatedTriangle {
+        InterpolatedTriangle::new(
+            Point::origin(),
+            Point::new(0., 1., 1.),
+            Point::new(0., 1., 0.),
+            Vector::x_axis(),
+            Vector::y_axis(),
+            Vector::z_axis(),
+        )
+    }
+
+    #[test]
+    fn normal_interpolation_at_c0_works() {
+        let triangle = simple_triangle();
+        let normal = triangle.normal(&Point::origin());
+        assert_eq!(normal, Vector::x_axis());
+    }
+
+    #[test]
+    fn normal_interpolation_at_c1_works() {
+        let triangle = simple_triangle();
+        let normal = triangle.normal(&Point::new(0., 1., 1.));
+        assert_eq!(normal, Vector::y_axis());
+    }
+
+    #[test]
+    fn normal_interpolation_at_c2_works() {
+        let triangle = simple_triangle();
+        let normal = triangle.normal(&Point::new(0., 1., 0.));
+        assert_eq!(normal, Vector::z_axis());
+    }
+
+    #[test]
+    fn normal_interpolation_at_center_works() {
+        let triangle = simple_triangle();
+        let center = Point::new(0., 2. / 3., 1. / 3.);
+        let normal = triangle.normal(&center);
+        let expected = Unit::new_normalize(Vector::new(1., 1., 1.));
+        assert!((normal.as_ref() - expected.as_ref()).magnitude() < 1e-5)
+    }
+
+    #[test]
+    fn deserialization_works() {
+        let yaml = r#"
+            corners:
+              - [0.0, 0.0, 0.0]
+              - [0.0, 1.0, 1.0]
+              - [0.0, 1.0, 0.0]
+            normals:
+              - [1.0, 0.0, 0.0]
+              - [0.0, 1.0, 0.0]
+              - [0.0, 0.0, 1.0]
+        "#;
+        let triangle: InterpolatedTriangle = serde_yaml::from_str(yaml).unwrap();
+        assert_eq!(
+            triangle,
+            InterpolatedTriangle::new(
+                Point::origin(),
+                Point::new(0., 1., 1.),
+                Point::new(0., 1., 0.),
+                Vector::x_axis(),
+                Vector::y_axis(),
+                Vector::z_axis(),
+            )
+        )
+    }
+}

pathtracer/src/shape/mesh.rs

@@ -0,0 +1,9 @@
+use super::{InterpolatedTriangle, Shape, Triangle};
+use crate::material::{Material, TriangleMaterial, UniformMaterial};
+use crate::texture::{Texture, TriangleTexture, UniformTexture};
+use crate::Point;
+use beevee::{
+    aabb::{Bounded, AABB},
+    bvh::Intersected,
+    ray::Ray,
+};

pathtracer/src/shape/mod.rs

@@ -14,42 +14,53 @@ use serde::Deserialize;
 #[serde(rename_all = "lowercase")]
 #[allow(missing_docs)]
 #[enum_dispatch::enum_dispatch]
-#[derive(Debug, PartialEq, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Deserialize)]
 pub enum ShapeEnum {
     Sphere,
     Triangle,
+    InterpolatedTriangle,
+}
+
+// FIXME: this has to be written by hand due to a limitation of `enum_dispatch` on super traits
+impl Bounded for ShapeEnum {
+    fn aabb(&self) -> AABB {
+        match self {
+            ShapeEnum::Sphere(s) => s.aabb(),
+            ShapeEnum::Triangle(s) => s.aabb(),
+            ShapeEnum::InterpolatedTriangle(s) => s.aabb(),
+        }
+    }
+
+    fn centroid(&self) -> Point {
+        match self {
+            ShapeEnum::Sphere(s) => s.centroid(),
+            ShapeEnum::Triangle(s) => s.centroid(),
+            ShapeEnum::InterpolatedTriangle(s) => s.centroid(),
+        }
+    }
+}
+
+impl Intersected for ShapeEnum {
+    fn intersect(&self, ray: &Ray) -> Option<f32> {
+        match self {
+            ShapeEnum::Sphere(s) => s.intersect(ray),
+            ShapeEnum::Triangle(s) => s.intersect(ray),
+            ShapeEnum::InterpolatedTriangle(s) => s.intersect(ray),
+        }
+    }
 }
 
 /// Represent an abstract shape inside the scene.
 #[enum_dispatch::enum_dispatch(ShapeEnum)]
-pub trait Shape: std::fmt::Debug {
-    /// Return the distance at which the object intersects with the ray, or None if it does not.
-    fn intersect(&self, ray: &Ray) -> Option<f32>;
+pub trait Shape: std::fmt::Debug + Intersected {
     /// Return the unit vector corresponding to the normal at this point of the shape.
     fn normal(&self, point: &Point) -> Unit<Vector>;
     /// Project the point from the shape's surface to its texel coordinates.
     fn project_texel(&self, point: &Point) -> Point2D;
-    /// Enclose the `Shape` in an axi-aligned bounding-box.
-    fn aabb(&self) -> AABB;
-    /// Return the centroid of the shape.
-    fn centroid(&self) -> Point;
 }
 
-impl Bounded for dyn Shape {
-    fn aabb(&self) -> AABB {
-        self.aabb()
-    }
-
-    fn centroid(&self) -> Point {
-        self.centroid()
-    }
-}
-
-impl Intersected for dyn Shape {
-    fn intersect(&self, ray: &Ray) -> Option<f32> {
-        self.intersect(ray)
-    }
-}
+mod interpolated_triangle;
+pub use interpolated_triangle::*;
 
 mod sphere;
 pub use sphere::*;

pathtracer/src/shape/sphere.rs

@@ -1,6 +1,7 @@
 use super::Shape;
 use crate::{Point, Point2D, Vector};
-use beevee::aabb::AABB;
+use beevee::aabb::{Bounded, AABB};
+use beevee::bvh::Intersected;
 use beevee::ray::Ray;
 use nalgebra::Unit;
 use serde::Deserialize;
@@ -38,6 +39,38 @@ impl Sphere {
 }
 
 impl Shape for Sphere {
+    fn normal(&self, point: &Point) -> Unit<Vector> {
+        let delt = if self.inverted {
+            self.center - point
+        } else {
+            point - self.center
+        };
+        Unit::new_normalize(delt)
+    }
+
+    fn project_texel(&self, point: &Point) -> Point2D {
+        // Project the sphere on the XY-plane
+        Point2D::new(
+            0.5 + (point.x - self.center.x) / (2. * self.radius),
+            0.5 + (point.y - self.center.y) / (2. * self.radius),
+        )
+    }
+}
+
+impl Bounded for Sphere {
+    fn aabb(&self) -> AABB {
+        let delt = Vector::new(self.radius, self.radius, self.radius);
+        let min = self.center - delt;
+        let max = self.center + delt;
+        AABB::with_bounds(min, max)
+    }
+
+    fn centroid(&self) -> Point {
+        self.center
+    }
+}
+
+impl Intersected for Sphere {
     fn intersect(&self, ray: &Ray) -> Option<f32> {
         use std::mem;
 
@@ -67,34 +100,6 @@ impl Shape for Sphere {
             Some(t_0)
         }
     }
-
-    fn normal(&self, point: &Point) -> Unit<Vector> {
-        let delt = if self.inverted {
-            self.center - point
-        } else {
-            point - self.center
-        };
-        Unit::new_normalize(delt)
-    }
-
-    fn project_texel(&self, point: &Point) -> Point2D {
-        // Project the sphere on the XY-plane
-        Point2D::new(
-            0.5 + (point.x - self.center.x) / (2. * self.radius),
-            0.5 + (point.y - self.center.y) / (2. * self.radius),
-        )
-    }
-
-    fn aabb(&self) -> AABB {
-        let delt = Vector::new(self.radius, self.radius, self.radius);
-        let min = self.center - delt;
-        let max = self.center + delt;
-        AABB::with_bounds(min, max)
-    }
-
-    fn centroid(&self) -> Point {
-        self.center
-    }
 }
 
 #[cfg(test)]

pathtracer/src/shape/triangle.rs

@@ -1,12 +1,14 @@
 use super::Shape;
 use crate::{Point, Point2D, Vector};
-use beevee::aabb::AABB;
+use beevee::aabb::{Bounded, AABB};
+use beevee::bvh::Intersected;
 use beevee::ray::Ray;
 use nalgebra::Unit;
-use serde::{Deserialize, Deserializer};
+use serde::Deserialize;
 
 /// Represent a triangle inside the scene.
-#[derive(Clone, Debug, PartialEq)]
+#[serde(from = "SerializedTriangle")]
+#[derive(Clone, Debug, PartialEq, Deserialize)]
 pub struct Triangle {
     c0: Point,
     c0c1: Vector,
@@ -38,7 +40,7 @@ impl Triangle {
         }
     }
 
-    fn barycentric(&self, point: &Point) -> Point2D {
+    pub(crate) fn barycentric(&self, point: &Point) -> Point2D {
         let c0_pos = point - self.c0;
         // P - A  =  u * (B - A) + v * (C - A)
         // (C - A) = v0 is c0c2
@@ -58,6 +60,29 @@ impl Triangle {
 }
 
 impl Shape for Triangle {
+    fn normal(&self, _: &Point) -> Unit<Vector> {
+        Unit::new_normalize(self.c0c1.cross(&self.c0c2))
+    }
+
+    fn project_texel(&self, point: &Point) -> Point2D {
+        self.barycentric(point)
+    }
+}
+
+impl Bounded for Triangle {
+    fn aabb(&self) -> AABB {
+        AABB::empty()
+            .grow(&self.c0)
+            .grow(&(self.c0 + self.c0c1))
+            .grow(&(self.c0 + self.c0c2))
+    }
+
+    fn centroid(&self) -> Point {
+        self.c0 + (self.c0c1 + self.c0c2) / 2.
+    }
+}
+
+impl Intersected for Triangle {
     fn intersect(&self, ray: &Ray) -> Option<f32> {
         let pvec = ray.direction.cross(&self.c0c2);
         let det = self.c0c1.dot(&pvec);
@@ -88,25 +113,6 @@ impl Shape for Triangle {
             Some(t)
         }
     }
-
-    fn normal(&self, _: &Point) -> Unit<Vector> {
-        Unit::new_normalize(self.c0c1.cross(&self.c0c2))
-    }
-
-    fn project_texel(&self, point: &Point) -> Point2D {
-        self.barycentric(point)
-    }
-
-    fn aabb(&self) -> AABB {
-        AABB::empty()
-            .grow(&self.c0)
-            .grow(&(self.c0 + self.c0c1))
-            .grow(&(self.c0 + self.c0c2))
-    }
-
-    fn centroid(&self) -> Point {
-        self.c0 + (self.c0c1 + self.c0c2) / 2.
-    }
 }
 
 #[derive(Debug, Deserialize)]
@@ -124,16 +130,6 @@ impl From<SerializedTriangle> for Triangle {
     }
 }
 
-impl<'de> Deserialize<'de> for Triangle {
-    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    where
-        D: Deserializer<'de>,
-    {
-        let cam: SerializedTriangle = Deserialize::deserialize(deserializer)?;
-        Ok(cam.into())
-    }
-}
-
 #[cfg(test)]
 mod test {
     use super::*;

pathtracer/src/texture/mod.rs

@@ -9,10 +9,11 @@ use serde::Deserialize;
 #[serde(rename_all = "lowercase")]
 #[allow(missing_docs)]
 #[enum_dispatch::enum_dispatch]
-#[derive(Debug, PartialEq, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Deserialize)]
 pub enum TextureEnum {
     #[serde(rename = "uniform")]
     UniformTexture,
+    TriangleTexture,
 }
 
 /// Represent an object's texture.
@@ -22,5 +23,8 @@ pub trait Texture: std::fmt::Debug {
     fn texel_color(&self, point: Point2D) -> LinearColor;
 }
 
+mod triangle;
+pub use triangle::*;
+
 mod uniform;
 pub use uniform::*;

pathtracer/src/texture/triangle.rs

@@ -0,0 +1,23 @@
+use super::{uniform::UniformTexture, Texture};
+use crate::core::LinearColor;
+use crate::Point2D;
+use serde::Deserialize;
+
+/// Represent a texture which interpolates between three points.
+#[derive(Debug, Clone, PartialEq, Deserialize)]
+pub struct TriangleTexture {
+    /// The texture at each point
+    textures: [UniformTexture; 3],
+}
+
+impl Texture for TriangleTexture {
+    fn texel_color(&self, point: Point2D) -> LinearColor {
+        let (u, v) = (point.x, point.y);
+        let sum = self.textures[0].texel_color(point) * (1. - u - v)
+            + self.textures[1].texel_color(point) * u
+            + self.textures[2].texel_color(point) * v;
+        sum / 3.
+    }
+}
+
+// FIXME: tests