The generated documentation of the engine, hosted on GitHub Pages

Raytracer

Lucien Rivière

45 commits
archived
Source code

Apr 2026 – May 2026 · BVH, camera maths, live preview and docs · team of 3 · last push 2026-05-21

A C++ raytracer where everything (shapes, materials, lights, output) is a plugin, sped up with a BVH, with a live preview window.

A red shiny sphere, a blue cylinder leaning to the right, a green cone lying on its side, a yellow cone standing up and a glass ball, on a pale floor against a slate wall — Every kind of shape and material in one scene: the file is below.

The same scene four times: seen from above, from the side, with the camera rolled so the floor slants, and stretched sideways so the sphere looks like an egg — The same scene through four cameras: moved up, turned, rolled, and stretched by a scale.

A rendered billiard scene: coloured balls racked on a pale blue table, with soft shadows — A scene from the repository, rendered by the engine itself.

500 shiny coloured spheres scattered on a plane, with shadows — 500 spheres: the kind of scene the speed-up is for.

The same scene as a heat map: dark far from the spheres, grey around them and red, yellow and blue where the rays cross the densest part — The same scene as a heat map of the work each ray needed: dark is cheap, hot colours are busy.

A raytracer draws a picture the way light works, backwards: it fires a ray through every pixel and follows it around a 3D scene. What does it hit, how is that surface lit, does it reflect? This one was built as a team for Epitech, around one rule: adding something new should never mean changing the engine.

How it works

Everything is a plug-in: shapes, materials, lights, even the way the picture is saved. A scene is a small text file, and adding a new kind of shape means writing one plug-in and naming it in a scene.

To keep big scenes fast, objects are grouped into nested boxes, so a ray that misses a box skips everything inside it. The heat map in the pictures shows it at work. A live window can also show the picture while it is being drawn.

A scene is read from a file like this one, which draws the first picture (download it). Shapes are placed and tilted by their own points and axes; the camera is the one thing that takes a full transform (position, rotation, scale).

camera:
{
    resolution = { width = 1280; height = 720; };
    position = { x = 0.0; y = -95.0; z = 22.0; };
    rotation = { x = 98.0; y = 0.0; z = 0.0; };   # degrees, applied X then Y then Z
    fieldOfView = 60.0;
};

primitives:
{
    cones = (
        # Apex up, axis pointing down: a finite cone standing on the floor
        { apex = { x = 32.0; y = 38.0; z = 24.0; }; axis = { x = 0.0; y = 0.0; z = -1.0; };
          radius = 10.0; height = 24.0; color = { r = 245.0; g = 190.0; b = 60.0; }; material = "lambertian"; }
    );
    # spheres, cylinders and planes follow the same pattern
};

lights:
{
    ambient = { multiplier = 0.25; color = { r = 255.0; g = 255.0; b = 255.0; }; };
    point = (
        { position = { x = -60.0; y = -40.0; z = 90.0; }; color = { r = 255.0; g = 245.0; b = 230.0; }; intensity = 0.8; }
    );
};

The documentation is generated from the code and published automatically, and the repository ships 23 sample scenes, from a billiard table to a rainbow corridor.

What I took from it

A clear boundary pays off once everyone respects it: new features arrive as new files instead of edits to the core.
The best speed-ups come from not doing work at all, here by skipping whole parts of the scene.

Raytracer

About this project

How it works

What I took from it

Cast