Add setting for width of dynamic snowline range for arctic tree placement

Default: 75%

src/landscape.cpp

@@ -105,6 +105,8 @@ static bool _is_main_river = false;
 byte _cached_snowline = 0;
 byte _cached_highest_snowline = 0;
 byte _cached_lowest_snowline = 0;
+byte _cached_tree_placement_highest_snowline = 0;
+byte _cached_tree_placement_lowest_snowline = 0;
 
 /**
  * Map 2D viewport or smallmap coordinate to 3D world or tile coordinate.
@@ -687,6 +689,10 @@ void UpdateCachedSnowLineBounds()
 {
 	_cached_highest_snowline = _snow_line == nullptr ? _settings_game.game_creation.snow_line_height : _snow_line->highest_value;
 	_cached_lowest_snowline = _snow_line == nullptr ? _settings_game.game_creation.snow_line_height : _snow_line->lowest_value;
+
+	uint snowline_delta = (((100 - _settings_game.construction.trees_around_snow_line_dynamic_range) * (HighestSnowLine() - LowestSnowLine())) + 50) / 100;
+	_cached_tree_placement_highest_snowline = HighestSnowLine() - ((snowline_delta + 1) / 2);
+	_cached_tree_placement_lowest_snowline = LowestSnowLine() + (snowline_delta / 2);
 }
 
 /**

src/landscape.h

@@ -51,6 +51,18 @@ inline byte LowestSnowLine()
 	return _cached_lowest_snowline;
 }
 
+inline byte HighestTreePlacementSnowLine()
+{
+	extern byte _cached_tree_placement_highest_snowline;
+	return _cached_tree_placement_highest_snowline;
+}
+
+inline byte LowestTreePlacementSnowLine()
+{
+	extern byte _cached_tree_placement_lowest_snowline;
+	return _cached_tree_placement_lowest_snowline;
+}
+
 int GetSlopeZInCorner(Slope tileh, Corner corner);
 Slope GetFoundationSlope(TileIndex tile, int *z = nullptr);
 

src/lang/english.txt

@@ -2204,6 +2204,8 @@ STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE                        :Adjusted arctic
 STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_HELPTEXT               :Adjust placement of trees around snow line in artic climate. Trees thin out above snowline. Trees are a mix of arctic and temperate just below snowline. Below that trees are temperate.
 STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_RANGE                  :Arctic tree range: {STRING2}
 STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_RANGE_HELPTEXT         :Approximate range of arctic trees around snow line
+STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_DYNAMIC_RANGE          :Seasonal snow line width for arctic trees: {STRING2}
+STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_DYNAMIC_RANGE_HELPTEXT :When using a seasonally variable snow line, what percentage of the snow line variation to use as the snow line for arctic tree placement. 0% uses the mid-point between summer and winter snow lines, 100% uses the whole range between the summer and winter snow lines.
 
 STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS                           :Build public roads connecting towns: {STRING2}
 STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS_HELPTEXT                  :Generates public roads which connect the towns. Takes a bit of time on bigger maps. 'Build and avoid' generates roads which avoid curves and result in very grid-like connections.

src/settings_gui.cpp

@@ -2224,6 +2224,7 @@ static SettingsContainer &GetSettingsTree()
 				treedist->Add(new SettingEntry("construction.extra_tree_placement"));
 				treedist->Add(new SettingEntry("construction.trees_around_snow_line_enabled"));
 				treedist->Add(new SettingEntry("construction.trees_around_snow_line_range"));
+				treedist->Add(new SettingEntry("construction.trees_around_snow_line_dynamic_range"));
 				treedist->Add(new SettingEntry("construction.tree_growth_rate"));
 			}
 

src/settings_type.h

@@ -441,6 +441,7 @@ struct ConstructionSettings {
 	uint8  extra_tree_placement;             ///< (dis)allow building extra trees in-game
 	uint8  trees_around_snow_line_range;     ///< range around snowline for mixed and arctic forest.
 	bool   trees_around_snow_line_enabled;   ///< enable mixed and arctic forest around snowline, and no trees above snowline
+	uint8  trees_around_snow_line_dynamic_range; ///< how much of the snow line dynamic range to use as the snowline for arctic tree placement
 	uint8  command_pause_level;              ///< level/amount of commands that can't be executed while paused
 	uint16 maximum_signal_evaluations;       ///< maximum number of programmable pre-signals which may be evaluated in one pass
 	bool   enable_build_river;               ///< enable building rivers in-game

src/table/settings/settings.ini

@@ -3803,6 +3803,20 @@ strval   = STR_JUST_COMMA
 cat      = SC_BASIC
 patxname = ""everest_treeline.construction.trees_around_snow_line_range""
 
+[SDT_VAR]
+var      = construction.trees_around_snow_line_dynamic_range
+type     = SLE_UINT8
+def      = 75
+min      = 0
+max      = 100
+interval = 5
+str      = STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_DYNAMIC_RANGE
+strhelp  = STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_DYNAMIC_RANGE_HELPTEXT
+strval   = STR_CONFIG_SETTING_PERCENTAGE
+cat      = SC_EXPERT
+patxname = ""everest_treeline.construction.trees_around_snow_line_dynamic_range""
+post_cb  = [](auto) { UpdateCachedSnowLineBounds(); }
+
 [SDT_VAR]
 var      = construction.tree_growth_rate
 type     = SLE_UINT8

src/tree_cmd.cpp

@@ -69,7 +69,7 @@ static bool CanPlantTreesOnTile(TileIndex tile, bool allow_desert)
 {
 	if ((_settings_game.game_creation.tree_placer == TP_PERFECT) &&
 		(_settings_game.game_creation.landscape == LT_ARCTIC) &&
-		(GetTileZ(tile) > (HighestSnowLine() + _settings_game.construction.trees_around_snow_line_range))) {
+		(GetTileZ(tile) > (HighestTreePlacementSnowLine() + _settings_game.construction.trees_around_snow_line_range))) {
 		return false;
 	}
 
@@ -196,11 +196,10 @@ static TreeType GetRandomTreeType(TileIndex tile, uint seed)
 			int z = GetTileZ(tile);
 			int height_above_snow_line = 0;
 
-			if (z > HighestSnowLine()) {
-				height_above_snow_line = z - HighestSnowLine();
-			}
-			else if (z < LowestSnowLine()) {
-				height_above_snow_line = z - LowestSnowLine();
+			if (z > HighestTreePlacementSnowLine()) {
+				height_above_snow_line = z - HighestTreePlacementSnowLine();
+			} else if (z < LowestTreePlacementSnowLine()) {
+				height_above_snow_line = z - LowestTreePlacementSnowLine();
 			}
 			uint normalised_distance = (height_above_snow_line < 0) ? -height_above_snow_line : height_above_snow_line + 1;
 			bool arctic_tree = false;
@@ -365,7 +364,7 @@ int MaxTreeCount(const TileIndex tile)
 
 	if (_settings_game.game_creation.landscape == LT_ARCTIC) {
 		if (_settings_game.construction.trees_around_snow_line_range != _previous_trees_around_snow_line_range) RecalculateArcticTreeOccuranceArray();
-		const uint height_above_snow_line = std::max<int>(0, tile_z - HighestSnowLine());
+		const uint height_above_snow_line = std::max<int>(0, tile_z - HighestTreePlacementSnowLine());
 		max_trees_snow_line_based = (height_above_snow_line < _arctic_tree_occurance.size()) ?
 			(1 + (_arctic_tree_occurance[height_above_snow_line] * 4) / 255) :
 			0;
@@ -976,7 +975,7 @@ static void TileLoop_Trees(TileIndex tile)
 						if (_settings_game.game_creation.tree_placer == TP_PERFECT &&
 							((_settings_game.game_creation.landscape != LT_TROPIC && GetTileZ(tile) <= GetSparseTreeRange()) ||
 								(GetTreeType(tile) == TREE_CACTUS) ||
-								(_settings_game.game_creation.landscape == LT_ARCTIC && GetTileZ(tile) >= HighestSnowLine() + _settings_game.construction.trees_around_snow_line_range / 3))) {
+								(_settings_game.game_creation.landscape == LT_ARCTIC && GetTileZ(tile) >= HighestTreePlacementSnowLine() + _settings_game.construction.trees_around_snow_line_range / 3))) {
 							// On lower levels we spread more randomly to not bunch up.
 							if (GetTreeType(tile) != TREE_CACTUS || (RandomRange(100) < 50)) {
 								PlantTreeAtSameHeight(tile);