Raytracing has always seemed like black magic to me. You write some code, and out comes a photorealistic image? It wasn’t until I built one myself that I understood the elegance of the algorithm.

What is Raytracing?

At its core, raytracing simulates how light travels. For each pixel in your image, you cast a ray into the scene and see what it hits. If it hits a reflective surface, you bounce the ray. If it hits a light source, you calculate the color.

Starting Simple

My first raytracer only handled:

  • Spheres (easiest shape to intersect)
  • Diffuse materials
  • Single point light
  • No shadows

Even with these constraints, the results were magical. Seeing a 3D sphere appear from math alone felt like conjuring something from nothing.

The Algorithm

for each pixel:
    ray = camera.get_ray(pixel)
    color = trace(ray)
    image[pixel] = color

trace(ray):
    if ray hits object at point:
        normal = object.normal_at(point)
        light_dir = normalize(light.pos - point)
        
        // Diffuse lighting
        intensity = max(0, dot(normal, light_dir))
        return object.color * intensity
    
    return background_color

Adding Features

Once the basics worked, I added:

  • Reflections: Bounce rays off shiny surfaces
  • Shadows: Check if light is blocked
  • Multiple lights: Sum contributions
  • Anti-aliasing: Multiple samples per pixel

Performance Reality Check

My Rust implementation renders a 800x600 image in about 30 seconds on a single thread. Compare that to real-time raytracing in modern games, and you appreciate how far hardware has come.

What’s Next?

I’m currently working on:

  • Triangles and mesh loading
  • Bounding volume hierarchies for faster intersection
  • Multi-threading with Rayon

Graphics programming is a deep rabbit hole, and I’m just getting started.