mirror of
https://gitlab.com/gaelysam/mapgen_rivers.git
synced 2024-11-14 06:40:21 +01:00
96 lines
3.6 KiB
Python
96 lines
3.6 KiB
Python
import numpy as np
|
|
import scipy.ndimage as im
|
|
from .rivermapper import flow
|
|
|
|
def advection(dem, dirs, rivers, time, K=1, m=0.5, sea_level=0):
|
|
"""
|
|
Simulate erosion by rivers.
|
|
This models erosion as an upstream advection of elevations ("erosion waves").
|
|
Advection speed depends on water flux and parameters:
|
|
|
|
v = K * flux^m
|
|
"""
|
|
|
|
adv_time = 1 / (K*rivers**m) # For every pixel, calculate the time an "erosion wave" will need to cross it.
|
|
dem = np.maximum(dem, sea_level)
|
|
dem_new = np.zeros(dem.shape)
|
|
|
|
for y in range(dirs.shape[0]):
|
|
for x in range(dirs.shape[1]):
|
|
# Elevations propagate upstream, so for every pixel we seek the downstream pixel whose erosion wave just reached the current pixel.
|
|
# This means summing the advection times downstream until we reach the erosion time.
|
|
x0, y0 = x, y
|
|
x1, y1 = x, y
|
|
remaining = time
|
|
while True:
|
|
# Move one pixel downstream
|
|
flow_dir = dirs[y0,x0]
|
|
if flow_dir == 0:
|
|
remaining = 0
|
|
break
|
|
elif flow_dir == 1:
|
|
y1 += 1
|
|
elif flow_dir == 2:
|
|
x1 += 1
|
|
elif flow_dir == 3:
|
|
y1 -= 1
|
|
elif flow_dir == 4:
|
|
x1 -= 1
|
|
|
|
if remaining <= adv_time[y0,x0]: # Time is over, we found it.
|
|
break
|
|
remaining -= adv_time[y0,x0]
|
|
x0, y0 = x1, y1
|
|
|
|
c = remaining / adv_time[y0,x0]
|
|
dem_new[y,x] = c*dem[y1,x1] + (1-c)*dem[y0,x0] # If between 2 pixels, perform linear interpolation.
|
|
|
|
return dem_new
|
|
|
|
def diffusion(dem, time, d=1):
|
|
radius = d * time**.5
|
|
if radius == 0:
|
|
return dem
|
|
return im.gaussian_filter(dem, radius, mode='reflect') # Diffusive erosion is a simple Gaussian blur
|
|
|
|
class EvolutionModel:
|
|
def __init__(self, dem, K=1, m=0.5, d=1, sea_level=0, flow=False, flex_radius=100, flow_method='semirandom'):
|
|
self.dem = dem
|
|
#self.bedrock = dem
|
|
self.K = K
|
|
self.m = m
|
|
self.d = d
|
|
self.sea_level = sea_level
|
|
self.flex_radius = flex_radius
|
|
self.define_isostasy()
|
|
self.flow_method = flow_method
|
|
#set_flow_method(flow_method)
|
|
if flow:
|
|
self.calculate_flow()
|
|
else:
|
|
self.lakes = dem
|
|
self.dirs = np.zeros(dem.shape, dtype=int)
|
|
self.rivers = np.zeros(dem.shape, dtype=int)
|
|
self.flow_uptodate = False
|
|
|
|
def calculate_flow(self):
|
|
self.dirs, self.lakes, self.rivers = flow(self.dem, method=self.flow_method)
|
|
self.flow_uptodate = True
|
|
|
|
def advection(self, time):
|
|
dem = advection(np.maximum(self.dem, self.lakes), self.dirs, self.rivers, time, K=self.K, m=self.m, sea_level=self.sea_level)
|
|
self.dem = np.minimum(dem, self.dem)
|
|
self.flow_uptodate = False
|
|
|
|
def diffusion(self, time):
|
|
self.dem = diffusion(self.dem, time, d=self.d)
|
|
self.flow_uptodate = False
|
|
|
|
def define_isostasy(self):
|
|
self.ref_isostasy = im.gaussian_filter(self.dem, self.flex_radius, mode='reflect') # Define a blurred version of the DEM that will be considered as the reference isostatic elevation.
|
|
|
|
def adjust_isostasy(self, rate=1):
|
|
isostasy = im.gaussian_filter(self.dem, self.flex_radius, mode='reflect') # Calculate blurred DEM
|
|
correction = (self.ref_isostasy - isostasy) * rate # Compare it with the reference isostasy
|
|
self.dem = self.dem + correction # Adjust
|