Implement water

[josauder]

Needs to be in roadmap submodule as flooded areas have to set the population density to 0.

roadmap/config_functions before or after roadmap/config_functions/setup_heightmap would be a good place.

Before caring about a GUI we need: A function flood which floods the heightmap when water is added at a certain height. It could look something like this:

def flood(heightmap, pos, h):
    """
    pos is a pair of indices on heightmap (position where it gets flooded)
    h is the corresponding height
    """
    flooded=np.zeros(heightmap.shape)

    stencil=np.array([
    [-1,0],
    [1,0],
    [0,1],
    [0,-1]
    ])

    front=[pos]
    while len(front)>0:
        new_front=[]
        for x in front:
            if heightmap[x]<h:
                flooded[x]=True
                new_front.extend(
                [new for new in x+stencil if not flooded[new] and not np.any(x<0) and not x[0]>heightmap.shape[0] and not x[1]>heightmap.shape[1]]
                )
        front=new_front

    return flooded

This is called every time the user wants to flood. When supplying a water image, this method has to be called until every flooded pixel was returned by flood() at least once.

[josauder]

We then need a function that finds bodies of land. If there is only one body of land (we have an ocean or something) then there is exactly one body of land. If we have e.g. a river seperating our land masses, then we need bridges. A draft for this function can be found in roadmap/config_functions/seperate