What I learned from writing a raytracer in Rust

Sometimes you learn the most by doing. That’s what I realized yet again when writing a toy raytracer in Rust during what little free time I had during paternity leave. I had religiously watched all of the Rust videos by No Boilerplate and needed to stop watching and start writing. I came across the Peter Shirley’s Raytracer In A Weekend tutorial, written in C++, and decided to try following along and writing it in Rust.

Last I left off, I was able to create a reflective material, which was fun.

Writing a toy raytracer in Rust helped me to fill some of the gaps in my learning so far, including:

• Traits
• Tuples
• Modules
• Operator Overloading
• Type Aliasing
• File I/O

Something that surprised me (but shouldn’t have) was that the C/C++ style of calling a method on mutable objects was noticeably less efficient than returning them. Kudos to Warren Henning for pointing this out when I was frustrated at the amount of time going into rendering a relatively small and simple image.

For example, any implementation of this C++ header:

class material {
    public:
        virtual bool scatter(
            const ray& r_in,       // input ray
            const hit_record& rec, // input hit record
            color& attenuation,    // output color if return value is true, otherwise nullref
            ray& scattered         // output ray if return value is true, otherwise nullref
        ) const = 0;
};

Was noticeably faster after simplified in Rust to:

pub trait Material {
    fn scatter(
        &self,
        ray: &Ray,
        hit_record: &HitRecord
    ) -> Option<(Color, Ray)>;
}

Whenever I get the time, I would love to rewrite the renderer from the beginning with multithreading, better command-line input/output, and overall cleaner code in mind. Beyond that, I’d love to expand it to have a scene file format, simple animations, a GUI, GPU support, and more.

For now, I want to finish off the Rustlings coding exercise and attempt to widen my range of Rust projects to include full-stack web development, artificial intelligence, and embedded development.