Lakes map: keep initial height (reduces file size)

Lake height is calculated for every basin, and there is a lake if lake height is higher than ground height. If it is lower, there is no lake.
In that case, it was previously raised to ground level, but since this can be done in Lua, we can write initial lakes height in the files.
This has the advantage of reducing file size, since there are bigger areas of equal values, that are more efficiently compressed.

terrainlib/erosion.py

@@ -11,12 +11,6 @@ def advection(dem, dirs, rivers, time, K=1, m=0.5, sea_level=0):
     v = K * flux^m
     """
 
-    dirs = dirs.copy()
-    dirs[0,:] = 0
-    dirs[-1,:] = 0
-    dirs[:,0] = 0
-    dirs[:,-1] = 0
-
     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)
@@ -51,7 +45,7 @@ def advection(dem, dirs, rivers, time, K=1, m=0.5, sea_level=0):
             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 np.minimum(dem, dem_new)
+    return dem_new
 
 def diffusion(dem, time, d=1):
     radius = d * time**.5
@@ -80,7 +74,7 @@ class EvolutionModel:
         self.flow_uptodate = True
 
     def advection(self, time):
-        dem = advection(self.lakes, self.dirs, self.rivers, time, K=self.K, m=self.m, sea_level=self.sea_level)
+        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
 

terrainlib/rivermapper.py

@@ -153,7 +153,7 @@ def flow(dem):
 
     waterq = accumulate_flow(dirs2)
 
-    return dirs2, np.maximum(basins[basin_id], dem), waterq
+    return dirs2, basins[basin_id], waterq
 
 def accumulate_flow(dirs):
     ndonors = np.zeros(dirs.shape, dtype=int)

terrainlib/view.py

@@ -22,11 +22,11 @@ if has_matplotlib:
     def view_map(dem, lakes, scale=1, title=None):
         lakes_sea = np.maximum(lakes, 0)
         water = np.maximum(lakes_sea - dem, 0)
-        max_elev = lakes_sea.max()
+        max_elev = dem.max()
         max_depth = water.max()
 
         ls = mcl.LightSource(azdeg=315, altdeg=45)
-        rgb = ls.shade(lakes_sea, cmap=cmap1, vert_exag=1/scale, blend_mode='soft', vmin=0, vmax=max_elev)
+        rgb = ls.shade(dem, cmap=cmap1, vert_exag=1/scale, blend_mode='soft', vmin=0, vmax=max_elev)
 
         (X, Y) = dem.shape
         extent = (0, Y*scale, 0, X*scale)
@@ -69,13 +69,13 @@ else:
     def plot(*args, **kwargs):
         pass
 
-def stats(dem, lake_dem, scale=1):
+def stats(dem, lakes, scale=1):
     surface = dem.size
 
-    continent = lake_dem >= 0
+    continent = np.maximum(dem, lakes) >= 0
     continent_surface = continent.sum()
 
-    lake = continent & (lake_dem>dem)
+    lake = continent & (lakes>dem)
     lake_surface = lake.sum()
 
     print('---   General    ---')