Pseudocode for field of view determination. Quite slick - real life example: http://noelfb.tumblr.com/post/53528361309

Field of View Pseudocode

// from http://roguebasin.roguelikedevelopment.org/index.php?title=Eligloscode

void FOV()
{
  float x,y;
  int i;
  CLEAR_MAP_TO_NOT_VISIBLE();//Initially set all tiles to not visible.
  for(i=0;i<360;i++)
  {
    x=cos((float)i*0.01745f);
    y=sin((float)i*0.01745f);
    DoFov(x,y);
  };
};

void DoFov(float x,float y)
{
  int i;
  float ox,oy;
  ox = (float)PLAYERX+0.5f;
  oy = (float)PLAYERY+0.5f;
  for(i=0;i<VIEW_RADIUS;i++)
  {
    MAP[(int)ox][(int)oy]=VISIBLE;//Set the tile to visible.
    if(MAP[(int)ox][(int)oy]==BLOCK)
      return;
    ox+=x;
    oy+=y;
  };
};