CODEWITHSUNDEEP
objective-calgorithmflood-fill
Alex Stone
Alex Stone

Reputation: 47364

Algorithm - how to use 2D Flood Fill with terrain cost?

I have two algorithms for movement in my game - one displays possible moves using Flood Fill, another calculates how to get to any possible location using A*.

Right now flood fill returns information in the following format

I'm interested in how I can use flood fill when I have variable move/terrain cost for each square.

Here's my current implementation, without move cost:

-(NSMutableArray*)getValidMovesFromPoint:(CGPoint)p lockMovesInTileset:(NSMutableArray*)tileset usingConnexity:(int)connexity
{
    int i = 0;
    NSMutableArray* validMovesFromThisPoint = [NSMutableArray array];//these tiles are valid moves from point

    NSNumber* tileIsWalkable = nil;

    //using (x,y) (0,0) as bottom left corner, Y axis pointing up, X axis pointing right
    i = [self indexFromPoint:CGPointMake(p.x-1, p.y)];//left
    tileIsWalkable = tileset[i];
    if(tileIsWalkable.boolValue == YES)
    {
        [self lockTileAtIndex:i forTileset:tileset rememberValidMovesInThisArray:validMovesFromThisPoint];
    };

    i = [self indexFromPoint:CGPointMake(p.x+1, p.y)];//right
    tileIsWalkable = tileset[i];
    if(tileIsWalkable.boolValue == YES)
    {
        [self lockTileAtIndex:i forTileset:tileset rememberValidMovesInThisArray:validMovesFromThisPoint];
    };

    i = [self indexFromPoint:CGPointMake(p.x, p.y-1)];//bottom
    tileIsWalkable = tileset[i];
    if(tileIsWalkable.boolValue == YES)
    {
        [self lockTileAtIndex:i forTileset:tileset rememberValidMovesInThisArray:validMovesFromThisPoint];
    };

    i = [self indexFromPoint:CGPointMake(p.x, p.y+1)];//top
    tileIsWalkable = tileset[i];
    if(tileIsWalkable.boolValue == YES)
    {
        [self lockTileAtIndex:i forTileset:tileset rememberValidMovesInThisArray:validMovesFromThisPoint];
    };

    if(connexity == 4){
        return validMovesFromThisPoint;//if we want a connexity 4, no need to go further
    }

    i = [self indexFromPoint:CGPointMake(p.x-1, p.y-1)];//bottom left
    tileIsWalkable = tileset[i];
    if(tileIsWalkable.boolValue == YES){
        [self lockTileAtIndex:i forTileset:tileset rememberValidMovesInThisArray:validMovesFromThisPoint];
    };

    i = [self indexFromPoint:CGPointMake(p.x+1, p.y-1)];//bottom right
    tileIsWalkable = tileset[i];
    if(tileIsWalkable.boolValue == YES){
        [self lockTileAtIndex:i forTileset:tileset rememberValidMovesInThisArray:validMovesFromThisPoint];
    };

    i = [self indexFromPoint:CGPointMake(p.x-1, p.y+1)];//top left
    tileIsWalkable = tileset[i];
    if(tileIsWalkable.boolValue == YES){
        [self lockTileAtIndex:i forTileset:tileset rememberValidMovesInThisArray:validMovesFromThisPoint];
    };

    i = [self indexFromPoint:CGPointMake(p.x+1, p.y+1)];///top right
    tileIsWalkable = tileset[i];
    if(tileIsWalkable.boolValue == YES){
        [self lockTileAtIndex:i forTileset:tileset rememberValidMovesInThisArray:validMovesFromThisPoint];
    };

    return validMovesFromThisPoint;
}

Upvotes: 0

Views: 556

Answers (1)

Alex Stone
Alex Stone

Reputation: 47364

Apparently flood fill cannot be used, instead I implemented Breadth First Search, as described in this post. This allows for terrain cost to be included in calculations

Upvotes: 1

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