Hello everyone,
I am busy with a school project in which I'm making a micromouse. Right now I've finished the micromouse and I've already programmed a code which uses right wall following. However, right now I'm stuck as I want to program a code using floodfill. I've already done a lot of research but I simply don't understand it how to implement floodfill in my code.
I did find this sketch, however I don't understand how it works though.
#define NORTH 1
#define EAST 2
#define SOUTH 4
#define WEST 8
#define VISITED 16
#define ONROUTE 32
#define NOTNORTH (255-NORTH)
#define NOTEAST (255-EAST)
#define NOTSOUTH (255-SOUTH)
#define NOTWEST (255-WEST)
#define ALLWALLS (NORTH|EAST|SOUTH|WEST)
// maze storage
#define NUMCELLS 256
extern CELL maze[NUMCELLS] ;
extern CELL map[NUMCELLS];
/*
floodMaze solves the maze using wall data found in the array maze
and places the flooding data - effectively the routemap - into
the array map. The destination cell is passed in to the function
to allow solving for any location.
The state of map on entry is not important and it is not important
whether all the walls have been found. The algorithm simply performs
the flood based on what it knows at the time it is called.
At worst, up to 255 passes are made through the maze date in generating
the map. If that many passes are made, there has been an error and
the maze should be considered to be seriously in error.
Passes of the algorithm are made until either the limit has been reached
or the change flag indicates that none of the map data has changed in
that pass. At that point the maze can be considered to have been solved.
Clearly, unless all the walls have been observed, the map will contain
invalid paths. The mouse will discover new walls and call the solver again
as needed.
The function returns the number of passes required to solve the maze.
A returned value of 255 indicates an error.
Note that the array is allowed to wrap around in a most dangerous
manner by relying on the 8 bit pointer.
This should not be a real problem in as much as the existence of the outer
walls means we never have to make use of the value
*/
UCHAR floodMaze(UCHAR goal)
{
UCHAR i,j;
UCHAR now,next;
UCHAR passes;
UCHAR cellwalls; // the wall data for a given cell
UCHAR changed;
i = 0;
do{
map[i--] = 255;
} while (i);
map[goal]=0;
passes = 0;
now = 0;
next = now+1;
do
{
changed = 0;
i = 0;
do
{
if (map[i]==now)
{
cellwalls=maze[i];
if ((cellwalls & NORTH) == 0)
{
j = i+1;
if (map[j] == 255){ map[j] = next; changed=1;}
}
if ((cellwalls & EAST) == 0)
{
j = i + 16;
if (map[j] == 255){ map[j] = next; changed=1;}
}
if ((cellwalls & SOUTH) == 0)
{
j = i + 255;
if (map[j] == 255){ map[j] = next; changed=1;}
}
if ((cellwalls & WEST) == 0)
{
j = i + 240;
if (map[j] == 255){ map[j] = next; changed=1;}
}
}
i--;
} while(i);
now = now+1;
next = now+1;
passes++;
} while(changed);
return passes;
}
Could anyone maybe help me explaining this code or just explaining how to implement floodfill in general?
Thank you before hand!
