Ufdjrw

I have been writing a Ray Caster in Rust following "The Ray Tracer Challenge", and I've been having a hard time figuring out the proper way to implement polymorphism in Rust. My priorities are that the object can be used in a multi-threaded program, and that seems to be the main problem.

I have two cases on this, but I'll focus on one: a shape. There are different kinds of shapes (sticking with the able suffix I originally called my trait Intersectable). Here was a working trait object implementation, but it didn't work with multi-threading:

#[derive(Debug)]
pub struct Shape 
 pub parent: Option<Arc<Shape>>,
 pub transform: Matrix4,
 pub material: Material,
 pub intersectable: Box<Intersectable>,

pub trait Intersectable: Debug + IntersectableClone 
 fn local_intersect(&self, ray: &Ray, object: Arc<Shape>) -> Vec<Intersection>;


pub trait IntersectableClone 
 fn clone_box(&self) -> Box<Intersectable>;


impl<T> IntersectableClone for T
where
 T: 'static + Intersectable + Clone,

 fn clone_box(&self) -> Box<Intersectable> 
 Box::new(self.clone())
 


impl Clone for Box<Intersectable> 
 fn clone(&self) -> Box<Intersectable> 
 self.clone_box()
 


#[derive(Clone, Debug)]
pub struct Sphere 

impl Intersectable for Sphere 
 fn local_intersect(&self, ray: &Ray, object: Arc<Shape>) -> Vec<Intersection> 
 ...sphere specific code
 


#[derive(Clone, Debug)]
pub struct Plane 

impl Intersectable for Plane 
 fn local_intersect(&self, ray: &Ray, object: Arc<Shape>) -> Vec<Intersection> 
 ...plane specific code
 

As a pure struct, with no official polymorphism, I've written a kind of static dispatch that looks like this:

#[derive(Debug, Clone)]
pub enum IntersectableType 
 Sphere,
 Plane,


#[derive(Debug, Clone)]
pub struct Intersectable 
 intersectable_type: IntersectableType,


impl Intersectable 
 pub fn local_intersect(&self, ray: &Ray, object: Arc<Shape>) -> Vec<Intersection> 
 match self.intersectable_type 
 IntersectableType::Sphere => self.local_intersect_sphere(ray, object),
 IntersectableType::Plane => self.local_intersect_plane(ray, object),
 _ => Vec::new(),
 
 

 fn local_intersect_sphere(&self, ray: &Ray, object: Arc<Shape>) -> Vec<Intersection> 
 ...sphere specific code
 

 fn local_intersect_plane(&self, ray: &Ray, object: Arc<Shape>) -> Vec<Intersection> 
 ...plane specific implementation
 

This works great, but it feels very non-Rusty. I've hit a few problems with using other implementations:
- Using Box<Intersectable> (when it was a Trait, not a struct), is difficult to clone (I copied How to clone a struct storing a boxed trait object? but didn't love having to use 'static, since that made concurrency impossible).
- Using Arc<Intersectable> seemed to have the same problems as Box, though maybe there is a way to make that work.

Is there a way to do this in Rust that allows me to take advantage of concurrency and not write manual static dispatch like this?