- Implement raycasting in a simple video game
git clone git@github.com:Bima42/cub3d.git
make
./cub3d maps/map.cub
-
Use W, A, S, D key to move
-
Use left and right arrow to rotate camera
-
Esc quit the game
- First part was the parsing
- Then, we split works in two parts : initialisation part (graphics, mlx ...) and raycasting part
- Extension file is .cub only
- Begin by texture path (N, S, E, W)
- Then some rgb data for ceiling and floor
- Empty lines can be found between those datas
- Must be surrounded by '1', filled by '0'
- Only one player spawn (N, S, E or W indicate player orientation)
- Q for exit map
For every rows and colums (x and y) :
- Start with skip white spaces
- Then we have to hit a wall
- We skip all char except wall (1) until white space or \0
- If the char in pos - 1 is not a wall, it's an error
- The fact is if we hit a wall we have to found another one, walls works by pair. If the second wall was not hit, row (or column) is false
Example for the x axis
int control_axis_x(char **map, int y, int max_y)
{
int x;
x = 0;
if (y == max_y)
return (1);
if (map[y][x] != '\0')
{
skip_white_space(map[y], &x);
while (map[y][x] == WALL && map[y][x] != '\0')
{
while (map[y][x] != '\0' && !is_w_space(map[y][x]))
x++;
if (map[y][x - 1] != WALL)
return (0);
skip_white_space(map[y], &x);
}
if (map[y][x] == '\0')
return (control_axis_x(map, y + 1, max_y));
else
return (0);
}
return (0);
}-
During this check, we extract the higher x and y to reformat_map, using white_spaces to reformat and put every lines at the same length.
-
Last line is filled with \0.
- Transforming a limited form of data into a three-dimensional projection with the help of tracing rays from the view point into the viewing volume.
- Rays can be cast and traced in groups based on certain geometric constraints.
- A ray from the pixel through the camera is obtained and the intersection of all objects in the picture is computed.
-
There some steps to cast rays:
- 1 : Based on the viewing angle, subtract 30 degrees (half of the FOV).
- 2 : Starting from column 0.
- 3 : Cast a ray.
- 4 : Trace the ray until it hits a wall.
- 5 : Record the distance to the wall (the distance = length of the ray).
- 6 : Add the angle increment so that the ray moves to the right
- 7 : Repeat steps from step 3 with a column+1. We gonna cast one ray per unit width
-
We have to create a maze world that has the following geometric constraints:
- Walls are always at 90° angle with the floor.
- Walls are made of cubes that have the same size.
- Floor is always flat.
-
Need to define some attributes :
- Player/viewer’s height, player’s field of view (FOV), and player’s position.
- Projection plane’s dimension.
- Relationship between player and projection plane.
- FOV of 60 is generally a good choice.
- Player height reprensent half of window height.
void raycasting(t_game *game)
{
game->column = 0;
game->rays.ang = game->p.vis + FOV / 2;
while (game->column < WIN_W)
{
check_rays_angle(game);
horizontal_raycasting(game);
vertical_raycasting(game);
draw(game);
game->rays.ang -= FOV / (double)WIN_W;
game->column++;
}
}- WARNING : You want to protect the player to go outside the 360 degrees available for rotation.
void check_rays_angle(t_game *game)
{
while (game->rays.ang >= 360)
game->rays.ang -= 360;
while (game->rays.ang < 0)
game->rays.ang += 360;
}- To ensure that each ray stops at the first wall touched, it is necessary to carry out a horizontal and vertical check
double horizontal_raycasting(t_game *game)
{
game->rays.tan = tan(deg_to_rad(game->rays.ang));
if (game->rays.ang > EAST && game->rays.ang < WEST)
{
game->rays.step_y = -TILE;
game->rays.hit_y = floor(game->p.y / TILE) * TILE - 0.00001;
}
else
{
game->rays.step_y = TILE;
game->rays.hit_y = floor(game->p.y / TILE) * TILE + TILE;
}
game->rays.hit_x = game->p.x
+ (game->p.y - game->rays.hit_y) / game->rays.tan;
if (game->rays.ang == NORTH || game->rays.ang == SOUTH)
game->rays.step_x = 0;
else
game->rays.step_x = TILE / game->rays.tan;
if (game->rays.ang > WEST)
game->rays.step_x *= -1;
digital_differential_analyzer(game);
return (sqrt(square((game->p.x - game->rays.hit_x))
+ square((game->p.y - game->rays.hit_y))));
}
double vertical_raycasting(t_game *game)
{
game->rays.tan = tan(deg_to_rad(game->rays.ang));
if (game->rays.ang < NORTH || game->rays.ang > SOUTH)
{
game->rays.step_x = TILE;
game->rays.hit_x = floor(game->p.x / TILE) * TILE + TILE;
}
else
{
game->rays.step_x = -TILE;
game->rays.hit_x = floor(game->p.x / TILE) * TILE - 0.00001;
}
game->rays.hit_y = game->p.y
+ (game->p.x - game->rays.hit_x) * game->rays.tan;
if (game->rays.ang == WEST || game->rays.ang == EAST)
game->rays.step_y = 0;
else
game->rays.step_y = TILE * (game->rays.tan * -1);
if (game->rays.ang >= NORTH && game->rays.ang <= SOUTH)
game->rays.step_y *= -1;
digital_differential_analyzer(game);
return (sqrt(square((game->p.x - game->rays.hit_x))
+ square((game->p.y - game->rays.hit_y))));
}- This algorithm is used to progress by step in each checker (vertical and horizontal)
- We have to move for 1 Tile width for horizontal checker, and 1 Tile height for vertical checker
void digital_differential_analyzer(t_game *game)
{
game->map_pos_x = game->rays.hit_x / (int)TILE;
game->map_pos_y = game->rays.hit_y / (int)TILE;
while (game->map_pos_x > 0 && game->map_pos_x < game->map_w
&& game->map_pos_y > 0 && game->map_pos_y < game->map_h
&& game->map[game->map_pos_y][game->map_pos_x] != '1')
{
if (game->map[game->map_pos_y][game->map_pos_x] == 'Q')
{
game->flag_exit = 1;
break ;
}
game->rays.hit_x += game->rays.step_x;
game->rays.hit_y += game->rays.step_y;
game->map_pos_x = game->rays.hit_x / (int)TILE;
game->map_pos_y = game->rays.hit_y / (int)TILE;
}
}- When horizontal and vertical intersections are merged, you have to check the lowest distance between player and wall using Pythagore theorem.
- Now you know which side of the wall you have to drawn.
- This way will show distortion called "fish-eye".
- To remove the viewing distortion :
correct_dist = distorted_dist * cos(angle);