Document conf files

There were sometimes missing water patches near a lake's edge, when the neighbour catchment area was lower.
This commit allows to divide a cell into several mini-catchment basins, to fill only a part of it with water.

README.md

@@ -55,6 +55,14 @@ Generic usage:
 - `conf_file`: Path to configuration file from which parameters should be read. If omitted, attempts to read in `terrain.conf`.
 - `output_dir`: Directory in which to save the grid data, defaults to `river_data/`. If it does not exist, it is created. If it already contains previous grid data, they are overwritten.
 
+#### Config files
+The mod currently includes 3 config files, providing different terrain styles:
+- `terrain_default.conf` generates the standard terrain, with highest elevations around 250 with sharp peaks, and otherwise hilly terrain.
+- `terrain_higher.conf` generates higher mountains (up to 400 nodes), and wider valleys.
+- `terrain_original.conf` provides a terrain similar to what was generated with the first release of `mapgen_rivers`.
+
+More work is needed to find better and more varied terrain styles.
+
 ### Complete list of parameters
 Other parameters can be specified by `--parameter value`. Syntax `--parameter=value` is also supported.
 
@@ -78,6 +86,7 @@ Other parameters can be specified by `--parameter value`. Syntax `--parameter=va
 | `niter`       | Number of iterations. Each iteration represents a time `time/niter`. | `--niter 10` |
 | `sea_level_variations` | Amplitude of sea level variations throughout the simulation (if any). | `--sea_level_variations 10` |
 | `sea_level_variations_time` | Characteristic time of variation for sea level, in the same units than `time`. Increasing it will result in slower variations between iterations. | `--sea_level_variations_time 1` |
+| `flow_method` | Algorithm used for local flow calculation. Possible values are `steepest` (every node flows toward the steepest neighbour when possible), and `semirandom` (default, flow direction is determined randomly between lower neighbours, with lowest ones having greater probability). | `--flow_method semirandom` |
 | | **Alternatives** |
 | `config`      | Another way to specify configuration file | `--config terrain_higher.conf` |
 | `output`      | Another way to specify output dir | `--output ~/.minetest/worlds/my_world/river_data` |

generate.py

@@ -29,7 +29,7 @@ def noisemap(X, Y, scale=0.01, vscale=1.0, offset=0.0, log=False, **params):
 ### PARSE COMMAND-LINE ARGUMENTS
 argc = len(sys.argv)
 
-config_file = 'terrain.conf'
+config_file = 'terrain_default.conf'
 output_dir = 'river_data'
 params_from_args = {}
 i = 1 # Index of arguments
@@ -80,13 +80,14 @@ offset = float(get_setting('offset', 0.0))
 persistence = float(get_setting('persistence', 0.6))
 lacunarity = float(get_setting('lacunarity', 2.0))
 
-K = float(get_setting('K', 1.0))
-m = float(get_setting('m', 0.35))
-d = float(get_setting('d', 0.2))
+K = float(get_setting('K', 0.5))
+m = float(get_setting('m', 0.5))
+d = float(get_setting('d', 0.5))
 sea_level = float(get_setting('sea_level', 0.0))
 sea_level_variations = float(get_setting('sea_level_variations', 0.0))
 sea_level_variations_time = float(get_setting('sea_level_variations_time', 1.0))
 flex_radius = float(get_setting('flex_radius', 20.0))
+flow_method = get_setting('flow_method', 'semirandom')
 
 time = float(get_setting('time', 10.0))
 niter = int(get_setting('niter', 10))
@@ -94,11 +95,6 @@ niter = int(get_setting('niter', 10))
 ### MAKE INITIAL TOPOGRAPHY
 n = np.zeros((mapsize+1, mapsize+1))
 
-if sea_level_variations != 0.0:
-    sea_ybase = np.random.randint(8192)-4096
-    sea_level_ref = snoise2(time * (1-1/niter) / sea_level_variations, sea_ybase, **params_sealevel) * sea_level_variations
-    offset -= (sea_level_ref + sea_level)
-
 # Set noise parameters
 params = {
     "offset" : offset,
@@ -115,12 +111,17 @@ params_sealevel = {
     "lacunarity" : 2,
 }
 
+if sea_level_variations != 0.0:
+    sea_ybase = np.random.randint(8192)-4096
+    sea_level_ref = snoise2(time * (1-1/niter) / sea_level_variations, sea_ybase, **params_sealevel) * sea_level_variations
+    params['offset'] -= (sea_level_ref + sea_level)
+
 n = noisemap(mapsize+1, mapsize+1, **params)
 
 ### COMPUTE LANDSCAPE EVOLUTION
 # Initialize landscape evolution model
 print('Initializing model')
-model = terrainlib.EvolutionModel(n, K=K, m=m, d=d, sea_level=sea_level, flex_radius=flex_radius)
+model = terrainlib.EvolutionModel(n, K=K, m=m, d=d, sea_level=sea_level, flex_radius=flex_radius, flow_method=flow_method)
 terrainlib.update(model.dem, model.lakes, t=5, sea_level=model.sea_level, title='Initializing...')
 
 dt = time/niter

heightmap.lua

@@ -99,7 +99,25 @@ local function heightmaps(minp, maxp)
 					xf, zf
 				))
 
-				local lake_height = math.max(math.floor(poly.lake), terrain_height)
+				-- Spatial gradient of the interpolation
+				local slope_x = zf*(vdem[3]-vdem[4]) + (1-zf)*(vdem[2]-vdem[1]) < 0
+				local slope_z = xf*(vdem[3]-vdem[2]) + (1-xf)*(vdem[4]-vdem[1]) < 0
+				local lake_id = 0
+				if slope_x then
+					if slope_z then
+						lake_id = 3
+					else
+						lake_id = 2
+					end
+				else
+					if slope_z then
+						lake_id = 4
+					else
+						lake_id = 1
+					end
+				end
+				local lake_height = math.max(math.floor(poly.lake[lake_id]), terrain_height)
+
 				if imax > 0 and depth_factor_max > 0 then
 					terrain_height = math.min(math.max(lake_height, sea_level) - math.floor(1+depth_factor_max*riverbed_slope), terrain_height)
 				end

polygons.lua

@@ -185,7 +185,7 @@ local function make_polygons(minp, maxp)
 
 			local poly_dem = {dem[iA], dem[iB], dem[iC], dem[iD]}
 			polygon.dem = poly_dem
-			polygon.lake = math.min(lakes[iA], lakes[iB], lakes[iC], lakes[iD])
+			polygon.lake = {lakes[iA], lakes[iB], lakes[iC], lakes[iD]}
 
 			-- Now, rivers.
 			-- Load river flux values for the 4 corners

terrain_default.conf

@@ -0,0 +1,17 @@
+mapsize = 1000
+scale = 400
+vscale = 300
+offset = 0
+persistence = 0.6
+lacunarity = 2.0
+
+K = 0.5
+m = 0.5
+d = 0.5
+sea_level = 0
+sea_level_variations = 8
+sea_level_variations_time = 2
+flex_radius = 20
+
+time = 10
+niter = 10

terrain_higher.conf

@@ -6,9 +6,11 @@ persistence = 0.65
 lacunarity = 2.0
 
 K = 0.5
-m = 0.55
-d = 0.45
+m = 0.45
+d = 0.55
 sea_level = 0
+sea_level_variations = 12
+sea_level_variations_time = 2
 flex_radius = 50
 
 time = 10

terrain_original.conf

@@ -4,10 +4,11 @@ vscale = 300
 offset = 0
 persistence = 0.6
 lacunarity = 2.0
+flow_method = steepest
 
-K = 0.5
-m = 0.5
-d = 0.5
+K = 1
+m = 0.35
+d = 0
 sea_level = 0
 flex_radius = 20
 

terrainlib/erosion.py

@@ -54,7 +54,7 @@ def diffusion(dem, time, d=1):
     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):
+    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
@@ -63,6 +63,8 @@ class EvolutionModel:
         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:
@@ -72,7 +74,7 @@ class EvolutionModel:
             self.flow_uptodate = False
 
     def calculate_flow(self):
-        self.dirs, self.lakes, self.rivers = flow(self.dem)
+        self.dirs, self.lakes, self.rivers = flow(self.dem, method=self.flow_method)
         self.flow_uptodate = True
 
     def advection(self, time):

terrainlib/rivermapper.py

@@ -12,7 +12,19 @@ from collections import defaultdict
 # The algorithm here makes use of most of the paper's concepts, including the Planar Boruvka algorithm.
 # Only flow_local and accumulate_flow are custom algorithms.
 
-def flow_local(plist):
+# Define two different method for local flow routing
+def flow_local_steepest(plist):
+    vmax = 0.0
+    imax = 0.0
+    for i, p in enumerate(plist):
+        if p > vmax:
+            vmax = p
+            imax = i
+    if vmax > 0.0:
+        return imax+1
+    return 0
+
+def flow_local_semirandom(plist):
     """
     Determines a flow direction based on denivellation for every neighbouring node.
     Denivellation must be positive for downward and zero for flat or upward:
@@ -27,7 +39,16 @@ def flow_local(plist):
             return i+1
         r -= p
 
-def flow(dem):
+flow_local_methods = {
+    'steepest' : flow_local_steepest,
+    'semirandom' : flow_local_semirandom,
+}
+
+def flow(dem, method='semirandom'):
+    if method in flow_local_methods:
+        flow_local = flow_local_methods[method]
+    else:
+        raise KeyError('Flow method \'{}\' does not exist'.format(method))
 
     # Flow locally
     dirs1 = np.zeros(dem.shape, dtype=int)