Cub3D

This project is inspired by the world-famous Wolfenstein 3D game.

The goal is to make a dynamic view inside a maze, in which you’ll have to find your way.

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Raycasting vs Raytracing

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.

Note: Raycasting is not the same as raytracing! Raycasting is a fast semi-3D technique that works in realtime even on 4MHz graphical calculators, while raytracing is a realistic rendering technique that supports reflections and shadows in true 3D scenes, and only recently computers became fast enough to do it in realtime for reasonably high resolutions and complex scenes.

Map

The cub3d executable receives as a single argument, the map file we read, which must be of .cub filetype.

The file must follow these rules:

• There must be header lines before the actual map containing the following:
  • At least a line containing NO, SO, EA and WE followed by a valid path to an xpm image
  • A line starting with F (floor) or C (ceiling) followed by a color in RGB separated by commas
• Only (empty), 1 (wall), 0 (floor), and either N, S, E or W (Player starting position looking at North, South, East or West), will be accepted characters in our map.
• The map may not be rectangular, but it must be surrounded by walls
• Spaces are allowed but the player cannot walk on them, thus every space must also be closed/surrounded by walls
• There must be a single player on the map

Algorithm

To calculate the distance between the player and the nearest wall, we can use the following algorithm:

1. Attributes needed for the projection:

Attribute	Description	Value
FOV	The field of view of the player	60º
HFOV	Half of the player's FOV	30º
Player's position	Center of the square where the player is	(int)(player_x + 0.5), (int)(player_y + 0.5)
Ray angle	Angle of the player view's direction	N (270º), S (90º), E (0º), W (180º)
Ray increment angle	Angle difference between one ray and the next one	2 * HFOV / window_width
Precision	Size of 'steps' taken every iteration	50
Limit	Limit of the distance the player can view	11

2. From the the player's position incrementing the x's and y's coordinates of the ray.

ray.x += ray_sin;
ray.y += ray_cos;

3. Repeat until we hit a wall.

4. Calculate the distance between the player's and the ray's position using the euclidean distance:

distance = sqrt(powf(x - pl.x - 0.5, 2.0) + powf(y - pl.y - 0.5, 2.0));

This algorith is repeated window_width times.
This distance is really helpful to calculate the height of the wall height:

wall_height = (window_height / (1.5 * distance));