Flood fill sometimes reaches beyond unit max allowed movement

[NathanLovato]

The flood fill algorithm will, in some cases, reach cells too far beyond an obstacle. we need to keep track of the walk distance of each cell in the function.

[RoloDMonkey]

I solved this problem using a distance-limited flood fill. https://www.redblobgames.com/grids/hexagons/#range-obstacles

It should be pretty easy to modify the current scripts. Here is what I did:

func distance_limited_flood_fill(start_cell: Vector2i, movement_range: int):

    var visited := Array()
    visited.append(start_cell)
    var fringes := Array()
    fringes.append([start_cell])

    for k in range(0, movement_range):
        fringes.append(Array())
        for center_cell in fringes[k]:
            for neighbor_cell in arena_tile_map.get_surrounding_cells(center_cell):
                if neighbor_cell in visited:
                    continue
                if cell_is_blocked(neighbor_cell):
                    continue
                visited.append(neighbor_cell)
                fringes[k + 1].append(neighbor_cell)

    return visited

This was written for Godot 4 and takes advantage of the fact that tilemaps now have a built-in get_surrounding_cells() function. In fact the project I am working on uses hexes, but the function works for any type of tilemap.

My cell_is_blocked() function is where you could put the existing code that checks if the cell is out of bounds, occupied by a unit, or has an obstacle.