Cub3D is a graphics project introducing the concept of raycasting. The graphics library used is MinilibX from 42. This was a group project, which I completed with the brilliant @rmnina (Who btw, created this beautiful README).

To quote Lode V. and their very good tutorial on raycasting :

“Raycasting is a rendering technique to create a 3D perspective in a 2D map. Back when computers were slower it wasn't possible to run real 3D engines in realtime, and raycasting was the first solution. Raycasting can go very fast, because only a calculation has to be done for every vertical line of the screen. The most well known game that used this technique, is of course Wolfenstein 3D”

The idea here is to recover a 2D map composed of :

• '0' for floors;
• '1' for walls;
• 'N', 'S', 'E' or 'W' for the observer's position and orientation.

We also retrieve a texture for each north, south, east and west side of the walls, and the colors of the floor and ceiling.

The maps have the .cub extension, and we've put plenty of examples in the maps/ folder (warning: some of these maps are invalid and were used to test our parsing!).

Now, the whole purpose of the project was to be able to go from that :

111111111111111111111111111
100000000000000000000000001
1000N0001110000001111100001
100000110110000010001100001
100001100110000000011000001
100011111111100000110000001
100000000110000011000000001
100000000110000111111000001
100000000000000000000000001
111111111111111111111111111

... to this :

This is where the raycasting technique comes into play. Basically, our observer will launch a bunch of rays, which will be traced step by step until they hit a wall. To calculate these rays, we use an algorithm called DDA (digital differential analyzer). This algorithm assumes that, since we're in a grid map, we'll always have intersections between our grid and our rays: we can use these intersections as stops, and advance our ray from intersection to intersection until we reach the wall.

Here's a little sheet @rmnina made when we were learning raycasting. Not that it necessarily make it any clearer, but at least that's nice.

For these notions, she followed this video.

Once we've got all our rays, we can use the distances obtained to calculate the size of the walls encountered, and thus give the perspective effect. And the result is…

Tadaaaa! It doesn't look like much, but in fact, it's a great example of what raycasting does: it just rescales squares according to their distance from the observer. Now it's just a matter of adding colors and textures to make the magic happen. Calculating the perspective of the textures is a bit tricky, but once it's done, it turns out like this:

Better, isn't it? The trick is done, it really looks like real 3D! From there, all we had to do was adjust our values to calculate our moves and rotations. We also thought it would be cool to add a minimap:

For the labyrinth, it helps... 🙂

Cub3D is an interesting graphics project. The raycasting technique enabled us to discover a practical application of maths as a means of creating algorithms, and to become even more familiar with graphics tools and techniques. Indeed, as well as successfully rendering a 2D map into 3D, we've also implemented vertical and lateral movements for the observer, as well as keyboard and mouse rotations. The search for optimization was also challenging, and we were pleased with the fluidity and final rendering.

git clone https://github.com/rmnina/cub3d.git
cd cub3d
git clone https://github.com/42Paris/minilibx-linux.git
make

./cub3D --help
                =========================================
                ███████╗██╗   ██╗██████╗ ██████╗ ██████╗  
                ██╔════╝██║   ██║██╔══██╗╚════██╗██╔══██╗
                ██║     ██║   ██║██████╔╝ █████╔╝██║  ██║
                ██║     ██║   ██║██╔══██╗ ╚═══██╗██║  ██║
                ╚██████╗╚██████╔╝██████╔╝██████╔╝██████╔╝
                 ╚═════╝ ╚═════╝ ╚═════╝ ╚═════╝ ╚═════╝ 
                =========================================

Cub3d program usage:
  ./cub3D file_path.cub

The file.cub should contain the following mandatory elements:
  - NO north_texture_path (Example: NO ./path_to_the_north_texture)
  - SO south_texture_path
  - WE west_texture_path
  - EA east_texture_path
  - F XXX,XXX,XXX (RGB format, for the Floor)
  - C XXX,XXX,XXX (RGB format, for the Ceiling)
  - A map

The map must fulfill the following specifications:
  - The map must be composed of only 6 possible characters: 
    • 0 for an empty space
    • 1 for a wall
    • N, S, E, or W for the player’s start position and orientation.
  - The map must be closed/surrounded by walls.
  - The map content always has to be the last element of the file.
see [-h] or [--help] for further informations

Tutorial from Lode V. that I highly recommend.

Memo sheet exists thanks to this video, but this one helped too.

And a bunch of our textures came from there.