cave.c

#include <inttypes.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <time.h>

// generation constants
#define CAVE_WIDTH  150
#define CAVE_HEIGHT 300
#define WALL_PROB   55
#define BIAS_DIV    30 // 16
#define CELL_ITER   8

enum {
  TILE_AIR,
  TILE_HARD,
  TILE_SOFT,
  TILE_WALL,
  TILE_FLOOR,
  TILE_LEN
};

uint8_t cave[CAVE_HEIGHT][CAVE_WIDTH];

void cell()
{
  // cellular automaton
  for (int y=1; y<CAVE_HEIGHT-1; y++) {
    for (int x=1; x<CAVE_WIDTH-1; x++) {
      int wall_count = 0;

      for (int j=-1; j<=1; j++) {
        for (int k=-1; k<=1; k++) {
          if (cave[y+j][x+k] == TILE_HARD)
            wall_count++;
        }
      }

      if (wall_count >= 5)
        cave[y][x] = TILE_HARD;
      else
        cave[y][x] = TILE_AIR;
    }
  }
}

void gen()
{
  srand(time(NULL));

  memset(cave, TILE_HARD, CAVE_WIDTH*CAVE_HEIGHT);

  // spawn initial wall cells
  for (int y=1; y<CAVE_HEIGHT-1; y++) {
    for (int x=1; x<CAVE_WIDTH-1; x++) {
      // uint32_t bias = 1+abs(CAVE_WIDTH/2-x)/BIAS_DIV;
      
      // its like, a circle or something
      uint32_t bias = 1 + abs(CAVE_WIDTH/2 - 1.8 * 
        sqrt((x - CAVE_WIDTH/2) * (x - CAVE_WIDTH/2)
        + 0.15 * (y - CAVE_HEIGHT/2) * (y - CAVE_HEIGHT/2)))/BIAS_DIV;
      
      if ((rand()%100) < WALL_PROB/bias)
        cave[y][x] = TILE_AIR;
    }
  }

  // do the cell automaton thingymajig
  for (int i=0; i<CELL_ITER; i++)
    cell();

  // beautify things a lil bit
  for (int y=1; y<CAVE_HEIGHT-1; y++) {
    for (int x=1; x<CAVE_WIDTH-1; x++) {
      if (cave[y-1][x] == TILE_HARD && cave[y+1][x] == TILE_AIR)
        cave[y][x] = TILE_SOFT;

      if (cave[y][x] == TILE_HARD) {
        if (cave[y][x+1] == TILE_AIR || cave[y][x-1] == TILE_AIR) {
          if (cave[y-1][x] == TILE_AIR)
            cave[y][x] = TILE_FLOOR;
          else
            cave[y][x] = TILE_WALL;
        }
      }
    }
  }
}

void main()
{
  gen();

  // debug print
  char tiles[TILE_LEN] = {
    ' ',
    '+',
    '#',
    '|',
    '_'
  };

  for (int y=0; y<CAVE_HEIGHT; y++) {
    for (int x=0; x<CAVE_WIDTH; x++) {
      printf("%c", tiles[cave[y][x]]);
    }
    printf("\n");
  }
}