mapgen_rivers/bounds.py

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import numpy as np
def make_bounds(dirs, rivers):
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"""
Give an array of all horizontal and vertical bounds
"""
(Y, X) = dirs.shape
bounds_h = np.zeros((Y, X-1), dtype='i4')
bounds_v = np.zeros((Y-1, X), dtype='i4')
bounds_v += (rivers * (dirs==1))[:-1,:]
bounds_h += (rivers * (dirs==2))[:,:-1]
bounds_v -= (rivers * (dirs==3))[1:,:]
bounds_h -= (rivers * (dirs==4))[:,1:]
return bounds_h, bounds_v
def get_fixed(dirs):
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"""
Give the list of points that should not be twisted
"""
borders = np.zeros(dirs.shape, dtype='?')
borders[-1,:] |= dirs[-1,:]==1
borders[:,-1] |= dirs[:,-1]==2
borders[0,:] |= dirs[0,:]==3
borders[:,0] |= dirs[:,0]==4
donors = np.zeros(dirs.shape, dtype='?')
donors[1:,:] |= dirs[:-1,:]==1
donors[:,1:] |= dirs[:,:-1]==2
donors[:-1,:] |= dirs[1:,:]==3
donors[:,:-1] |= dirs[:,1:]==4
return borders | ~donors
def twist(bounds_x, bounds_y, fixed, d=0.1, n=5):
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"""
Twist the grid (define an offset for every node). Model river bounds as if they were elastics.
Smoothes preferentially big rivers.
"""
moveable = ~fixed
(Y, X) = fixed.shape
offset_x = np.zeros((Y, X))
offset_y = np.zeros((Y, X))
for i in range(n):
force_long = np.abs(bounds_x) * (1+np.diff(offset_x, axis=1))
force_trans = np.abs(bounds_y) * np.diff(offset_x, axis=0)
force_x = np.zeros((Y, X))
force_x[:,:-1] = force_long
force_x[:,1:] -= force_long
force_x[:-1,:]+= force_trans
force_x[1:,:] -= force_trans
force_long = np.abs(bounds_y) * (1+np.diff(offset_y, axis=0))
force_trans = np.abs(bounds_x) * np.diff(offset_y, axis=1)
force_y = np.zeros((Y, X))
force_y[:-1,:] = force_long
force_y[1:,:] -= force_long
force_y[:,:-1]+= force_trans
force_y[:,1:] -= force_trans
length = np.hypot(force_x, force_y)
length[length==0] = 1
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coeff = d / length * moveable # Normalize, take into account the direction only
offset_x += force_x * coeff
offset_y += force_y * coeff
return offset_x, offset_y