barnsleys fern.c

#include <SDL/SDL.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>

#define SIZE 800
#define PRECISION 300000

struct paird{
  double x, y;
};

void draw_pixel(SDL_Surface * screen, int x, int y, int r, int g, int b){
  *((Uint32*)screen->pixels + y * screen->w + x) = (Uint32)SDL_MapRGB(screen->format, r, g, b);
}
void draw_pixel(SDL_Surface * screen, int x, int y, int c){
  draw_pixel(screen, x, y, c, c, c);
}

paird foo1(paird xy){
  return {
    0.0, 0.16 * xy.y
  };
}
paird foo2(paird xy){
  return {
    0.85 * xy.x + 0.04 * xy.y,
    -0.04 * xy.x + 0.85 * xy.y + 1.6
  };
}
paird foo3(paird xy){
  return {
    0.2 * xy.x - 0.26 * xy.y,
    0.23 * xy.x + 0.22 * xy.y + 1.6
  };
}
paird foo4(paird xy){
  return {
    -0.15 * xy.x + 0.28 * xy.y,
    0.26 * xy.x + 0.24 * xy.y + 0.44
  };
}

void render_world(SDL_Surface * screen){
  paird xy = {0.0, 0.0};

  int which;
  int x, y;
  for (int i = 0; i < PRECISION; i++){
    x = SIZE * (xy.x / 6 + 0.5);
    y = SIZE * (1.0 - xy.y / 10);

    if (x >= 0 && x < SIZE && y >= 0 && y < SIZE){
      draw_pixel(screen, x, y, 0, 192, 0);
    }

    which = rand() % 100;

    if (which < 1){
      xy = foo1(xy);
    }else if (which < 86){
      xy = foo2(xy);
    }else if (which < 94){
      xy = foo3(xy);
    }else{
      xy = foo4(xy);
    }
  }
}

void render(SDL_Surface * screen){
  SDL_FillRect(screen, NULL, SDL_MapRGB(screen->format, 0, 0, 0));
  render_world(screen);
  SDL_UpdateRect(screen, 0, 0, 0, 0);
}

int main(){
  SDL_Surface * screen;
  SDL_Event evt;

  SDL_Init(SDL_INIT_VIDEO);

  srand((unsigned)time(NULL));

  screen = SDL_SetVideoMode(SIZE, SIZE, 32, SDL_HWSURFACE);

  render(screen);
  while(1){
    if (SDL_PollEvent(&evt)){
      if(evt.type == SDL_QUIT) break;
    }
    SDL_Delay(1);
  }
  SDL_Quit();
}