Add dyn keyword to trait usage

README.md

@@ -1,6 +1,11 @@
 # Path Tracer
 
-A simple path tracer implemented in Rust following [Ray Tracing in One Weekend](https://github.com/petershirley/raytracinginoneweekend). This is a learning project for both Rust and ray tracing.
+A simple path tracer implemented in Rust following the C++ book [Ray Tracing in One Weekend](https://github.com/petershirley/raytracinginoneweekend). This is a learning project for both Rust and ray tracing.
 
 Scene output (fewer pixels and more samples than the end-of-book code):
 ![mapped-image](https://user-images.githubusercontent.com/81553/51091108-eac4c800-1753-11e9-8ed0-08aa7495bef9.png)
+
+## Building and running
+
+Run in release mode to avoid having your render take all day:
+`cargo run --release`

path_tracing/src/hitable.rs

@@ -8,7 +8,7 @@ pub struct HitRecord<'a> {
     pub t: f64,
     pub p: Vec3,
     pub normal: Vec3,
-    pub material: &'a Scattering,
+    pub material: &'a dyn Scattering,
 }
 
 impl<'a> HitRecord<'a> {

path_tracing/src/lib.rs

@@ -81,14 +81,3 @@ pub fn trace_scene(
 
     colors
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn mapping_a_collection() {
-        let columns = 4;
-        let rows = 2;
-    }
-}

path_tracing/src/sphere.rs

@@ -5,7 +5,7 @@ use super::{HitRecord, Hitable, Scattering};
 pub struct Sphere {
     pub center: Vec3,
     pub radius: f64,
-    pub material: Box<Scattering + Sync>, // for testability, would be easier not to complect with materials
+    pub material: Box<dyn Scattering + Sync>, // for testability, would be easier not to complect with materials
 }
 
 impl Hitable for Sphere {

path_tracing/src/world.rs

@@ -1,7 +1,7 @@
 use super::hitable::*;
 use super::Ray;
 
-pub struct World(Vec<Box<Hitable + Sync>>);
+pub struct World(Vec<Box<dyn Hitable + Sync>>);
 
 impl Hitable for World {
     fn hit(&self, ray: &Ray, t_min: f64, t_max: f64) -> Option<HitRecord> {
@@ -22,7 +22,7 @@ impl World {
         World(vec![])
     }
 
-    pub fn push(&mut self, item: Box<Hitable + Sync>) {
+    pub fn push(&mut self, item: Box<dyn Hitable + Sync>) {
         self.0.push(item);
     }
 }