(svn r16166) -Add [NoAI]: AITile::Get(Min|Max|Corner)Height

6 files changed, 294 insertions, 101 deletions

diff --git a/bin/ai/regression/regression.nut b/bin/ai/regression/regression.nut
index 02f2e55bf..8b77879bd 100644
--- a/bin/ai/regression/regression.nut
+++ b/bin/ai/regression/regression.nut
@@ -1189,7 +1189,7 @@ function Regression::TileList()
 	print("");
 	print("--TileList--");
 	print("  Count():             " + list.Count());
-	list.AddRectangle(41895 - 256 * 2, 256 * 2 + 41895 + 8);
+	list.AddRectangle(34436, 256 * 2 + 34436 + 8);
 	print("  Count():             " + list.Count());
 
 	list.Valuate(AITile.GetHeight);
@@ -1200,6 +1200,30 @@ function Regression::TileList()
 		print("    " + i + " => " + list.GetValue(i));
 	}
 
+	list.Valuate(AITile.GetCornerHeight, AITile.CORNER_N);
+	print("  CornerHeight(North): done");
+	print("  Count():             " + list.Count());
+	print("  ListDump:");
+	for (local i = list.Begin(); list.HasNext(); i = list.Next()) {
+		print("    " + i + " => " + list.GetValue(i));
+	}
+
+	list.Valuate(AITile.GetMinHeight);
+	print("  MinHeight():         done");
+	print("  Count():             " + list.Count());
+	print("  ListDump:");
+	for (local i = list.Begin(); list.HasNext(); i = list.Next()) {
+		print("    " + i + " => " + list.GetValue(i));
+	}
+
+	list.Valuate(AITile.GetMaxHeight);
+	print("  MaxHeight():         done");
+	print("  Count():             " + list.Count());
+	print("  ListDump:");
+	for (local i = list.Begin(); list.HasNext(); i = list.Next()) {
+		print("    " + i + " => " + list.GetValue(i));
+	}
+
 	list.Valuate(AITile.GetSlope);
 	list.KeepValue(0);
 	print("  Slope():             done");
@@ -1210,6 +1234,8 @@ function Regression::TileList()
 		print("    " + i + " => " + list.GetValue(i));
 	}
 
+	list.Clear();
+	list.AddRectangle(41895 - 256 * 2, 256 * 2 + 41895 + 8);
 	list.Valuate(AITile.IsBuildable);
 	list.KeepValue(1);
 	print("  Buildable():         done");
diff --git a/bin/ai/regression/regression.txt b/bin/ai/regression/regression.txt
index c3c793179..5a7c96d2a 100644
--- a/bin/ai/regression/regression.txt
+++ b/bin/ai/regression/regression.txt
@@ -7366,125 +7366,178 @@
 
 --TileList--
   Count():             0
-  Count():             45
+  Count():             27
   Height():            done
-  Count():             45
+  Count():             27
   ListDump:
-    42411 => 2
-    42410 => 2
-    42409 => 2
-    42408 => 2
-    42407 => 2
-    42154 => 2
-    42153 => 2
-    42152 => 2
-    42151 => 2
-    41898 => 2
-    41897 => 2
-    41896 => 2
-    41895 => 2
-    41642 => 2
-    41641 => 2
-    41640 => 2
-    41639 => 2
-    41386 => 2
-    41385 => 2
-    41384 => 2
-    41383 => 2
-    42415 => 1
-    42414 => 1
-    42413 => 1
-    42412 => 1
-    42159 => 1
-    42158 => 1
-    42157 => 1
-    42156 => 1
-    42155 => 1
-    41903 => 1
-    41902 => 1
-    41901 => 1
-    41900 => 1
-    41899 => 1
-    41647 => 1
-    41646 => 1
-    41645 => 1
-    41644 => 1
-    41643 => 1
-    41391 => 1
-    41390 => 1
-    41389 => 1
-    41388 => 1
-    41387 => 1
+    34956 => 4
+    34700 => 4
+    34444 => 4
+    34955 => 3
+    34954 => 3
+    34953 => 3
+    34699 => 3
+    34698 => 3
+    34697 => 3
+    34693 => 3
+    34692 => 3
+    34443 => 3
+    34442 => 3
+    34441 => 3
+    34439 => 3
+    34438 => 3
+    34437 => 3
+    34436 => 3
+    34952 => 2
+    34951 => 2
+    34950 => 2
+    34949 => 2
+    34948 => 2
+    34696 => 2
+    34695 => 2
+    34694 => 2
+    34440 => 2
+  CornerHeight(North): done
+  Count():             27
+  ListDump:
+    34956 => 4
+    34700 => 4
+    34444 => 4
+    34955 => 3
+    34954 => 3
+    34953 => 3
+    34699 => 3
+    34698 => 3
+    34697 => 3
+    34693 => 3
+    34692 => 3
+    34443 => 3
+    34442 => 3
+    34441 => 3
+    34439 => 3
+    34438 => 3
+    34437 => 3
+    34436 => 3
+    34952 => 2
+    34951 => 2
+    34950 => 2
+    34949 => 2
+    34948 => 2
+    34696 => 2
+    34695 => 2
+    34694 => 2
+    34440 => 2
+  MinHeight():         done
+  Count():             27
+  ListDump:
+    34956 => 4
+    34700 => 4
+    34444 => 4
+    34955 => 3
+    34954 => 3
+    34953 => 3
+    34699 => 3
+    34698 => 3
+    34697 => 3
+    34443 => 3
+    34442 => 3
+    34441 => 3
+    34436 => 3
+    34952 => 2
+    34951 => 2
+    34950 => 2
+    34949 => 2
+    34948 => 2
+    34696 => 2
+    34695 => 2
+    34694 => 2
+    34693 => 2
+    34692 => 2
+    34440 => 2
+    34439 => 2
+    34438 => 2
+    34437 => 2
+  MaxHeight():         done
+  Count():             27
+  ListDump:
+    34956 => 4
+    34955 => 4
+    34700 => 4
+    34699 => 4
+    34444 => 4
+    34443 => 4
+    34954 => 3
+    34953 => 3
+    34952 => 3
+    34951 => 3
+    34950 => 3
+    34949 => 3
+    34948 => 3
+    34698 => 3
+    34697 => 3
+    34696 => 3
+    34693 => 3
+    34692 => 3
+    34442 => 3
+    34441 => 3
+    34440 => 3
+    34439 => 3
+    34438 => 3
+    34437 => 3
+    34436 => 3
+    34695 => 2
+    34694 => 2
   Slope():             done
   KeepValue(0):        done
-  Count():             38
+  Count():             12
   ListDump:
-    42415 => 0
-    42414 => 0
-    42413 => 0
-    42410 => 0
-    42409 => 0
-    42408 => 0
-    42407 => 0
-    42159 => 0
-    42158 => 0
-    42157 => 0
-    42156 => 0
-    42153 => 0
-    42152 => 0
-    42151 => 0
-    41903 => 0
-    41902 => 0
-    41901 => 0
-    41900 => 0
-    41899 => 0
-    41897 => 0
-    41896 => 0
-    41895 => 0
-    41647 => 0
-    41646 => 0
-    41645 => 0
-    41644 => 0
-    41643 => 0
-    41641 => 0
-    41640 => 0
-    41639 => 0
-    41391 => 0
-    41390 => 0
-    41389 => 0
-    41388 => 0
-    41387 => 0
-    41385 => 0
-    41384 => 0
-    41383 => 0
+    34956 => 0
+    34954 => 0
+    34953 => 0
+    34700 => 0
+    34698 => 0
+    34697 => 0
+    34695 => 0
+    34694 => 0
+    34444 => 0
+    34442 => 0
+    34441 => 0
+    34436 => 0
   Buildable():         done
   KeepValue(1):        done
-  Count():             28
+  Count():             35
   BuildableRectangle(3, 3) ListDump:
     42415 => 1
     42414 => 1
     42413 => 1
+    42412 => 1
+    42411 => 1
     42410 => 1
     42159 => 1
     42158 => 1
     42157 => 1
     42156 => 1
+    42155 => 1
+    42154 => 1
     41903 => 1
     41902 => 1
     41901 => 1
     41900 => 1
     41899 => 1
+    41898 => 1
     41647 => 1
     41646 => 1
     41645 => 1
     41644 => 1
     41643 => 1
+    41642 => 1
     41641 => 1
     41391 => 1
     41390 => 1
     41389 => 1
     41388 => 1
     41387 => 1
+    41386 => 1
     41385 => 1
     42153 => 0
     41897 => 0
@@ -7496,26 +7549,33 @@
     42413 => 173
     42158 => 173
     41903 => 173
+    42412 => 172
     42157 => 172
     41902 => 172
     41647 => 172
+    42411 => 171
     42156 => 171
     41901 => 171
     41646 => 171
     41391 => 171
     42410 => 170
+    42155 => 170
     41900 => 170
     41645 => 170
     41390 => 170
+    42154 => 169
     41899 => 169
     41644 => 169
     41389 => 169
     42153 => 168
+    41898 => 168
     41643 => 168
     41388 => 168
     41897 => 167
+    41642 => 167
     41387 => 167
     41641 => 166
+    41386 => 166
     41385 => 165
     41384 => 164
   DistanceSquareToTile(30000) ListDump:
@@ -7532,17 +7592,24 @@
     42157 => 17834
     41390 => 17812
     41901 => 17741
+    42412 => 17680
     41645 => 17650
     42156 => 17585
     41389 => 17561
     41900 => 17492
+    42411 => 17433
     41644 => 17401
+    42155 => 17338
     41388 => 17312
     41899 => 17245
     42410 => 17188
     41643 => 17154
+    42154 => 17093
     41387 => 17065
+    41898 => 17000
+    41642 => 16909
     42153 => 16850
+    41386 => 16820
     41897 => 16757
     41641 => 16666
     41385 => 16577
@@ -7551,63 +7618,77 @@
     42415 => -1
     42414 => -1
     42413 => -1
+    42412 => -1
+    42411 => -1
     42410 => -1
     42159 => -1
     42158 => -1
     42157 => -1
     42156 => -1
+    42155 => -1
+    42154 => -1
     42153 => -1
     41903 => -1
     41902 => -1
     41901 => -1
     41900 => -1
     41899 => -1
+    41898 => -1
     41897 => -1
     41647 => -1
     41646 => -1
     41645 => -1
     41644 => -1
     41643 => -1
+    41642 => -1
     41641 => -1
     41391 => -1
     41390 => -1
     41389 => -1
     41388 => -1
     41387 => -1
+    41386 => -1
     41385 => -1
     41384 => -1
   GetClosestTown() ListDump:
     42415 => 3
     42414 => 3
     42413 => 3
+    42412 => 3
+    42411 => 3
     42410 => 3
     42159 => 3
     42158 => 3
     42157 => 3
     42156 => 3
+    42155 => 3
+    42154 => 3
     42153 => 3
     41903 => 3
     41902 => 3
     41901 => 3
     41900 => 3
     41899 => 3
+    41898 => 3
     41897 => 3
     41647 => 3
     41646 => 3
     41645 => 3
     41644 => 3
     41643 => 3
+    41642 => 3
     41641 => 3
     41391 => 3
     41390 => 3
     41389 => 3
     41388 => 3
     41387 => 3
+    41386 => 3
     41385 => 3
     41384 => 3
   CargoAcceptance():   done
   KeepAboveValue(10):  done
-  Count():             9
+  Count():             15
   ListDump:
     41897 => 29
     41385 => 26
@@ -7615,9 +7696,15 @@
     42153 => 25
     41641 => 23
     41899 => 17
+    41898 => 17
     41387 => 17
+    41386 => 17
     41643 => 14
+    41642 => 14
+    42411 => 13
     42410 => 13
+    42155 => 13
+    42154 => 13
   RoadTile():          done
   KeepValue(1):        done
   Count():             0
diff --git a/src/ai/api/ai_tile.cpp b/src/ai/api/ai_tile.cpp
index 8a04c1772..f5bf96f1a 100644
--- a/src/ai/api/ai_tile.cpp
+++ b/src/ai/api/ai_tile.cpp
@@ -11,6 +11,7 @@
 #include "../../water_map.h"
 #include "../../clear_map.h"
 #include "../../town.h"
+#include "../../landscape.h"
 
 /* static */ bool AITile::IsBuildable(TileIndex tile)
 {
@@ -132,11 +133,34 @@
 
 /* static */ int32 AITile::GetHeight(TileIndex tile)
 {
-	if (!::IsValidTile(tile)) return false;
+	if (!::IsValidTile(tile)) return -1;
 
 	return ::TileHeight(tile);
 }
 
+/* static */ int32 AITile::GetMinHeight(TileIndex tile)
+{
+	if (!::IsValidTile(tile)) return -1;
+
+	return ::GetTileZ(tile) / ::TILE_HEIGHT;
+}
+
+/* static */ int32 AITile::GetMaxHeight(TileIndex tile)
+{
+	if (!::IsValidTile(tile)) return -1;
+
+	return ::GetTileMaxZ(tile) / ::TILE_HEIGHT;
+}
+
+/* static */ int32 AITile::GetCornerHeight(TileIndex tile, Corner corner)
+{
+	if (!::IsValidTile(tile) || !::IsValidCorner((::Corner)corner)) return -1;
+
+	uint z;
+	::Slope slope = ::GetTileSlope(tile, &z);
+	return (z + ::GetSlopeZInCorner(slope, (::Corner)corner)) / ::TILE_HEIGHT;
+}
+
 /* static */ AICompany::CompanyID AITile::GetOwner(TileIndex tile)
 {
 	if (!::IsValidTile(tile)) return AICompany::COMPANY_INVALID;
diff --git a/src/ai/api/ai_tile.hpp b/src/ai/api/ai_tile.hpp
index 772b9e1bb..808bbcf52 100644
--- a/src/ai/api/ai_tile.hpp
+++ b/src/ai/api/ai_tile.hpp
@@ -32,7 +32,19 @@ public:
 	};
 
 	/**
-	 * Enumeration for the slope-type (from slopes.h).
+	 * Enumeration for corners of tiles.
+	 */
+	enum Corner {
+		CORNER_W       = 0,      //!< West corner
+		CORNER_S       = 1,      //!< South corner
+		CORNER_E       = 2,      //!< East corner
+		CORNER_N       = 3,      //!< North corner
+
+		CORNER_INVALID = 0xFF,
+	};
+
+	/**
+	 * Enumeration for the slope-type.
 	 *
 	 * This enumeration use the chars N, E, S, W corresponding the
 	 *  direction North, East, South and West. The top corner of a tile
@@ -41,18 +53,18 @@ public:
 	enum Slope {
 		/* Values are important, as they represent the internal state of the game. */
 		SLOPE_FLAT     = 0x00,                                  //!< A flat tile
-		SLOPE_W        = 0x01,                                  //!< The west corner of the tile is raised
-		SLOPE_S        = 0x02,                                  //!< The south corner of the tile is raised
-		SLOPE_E        = 0x04,                                  //!< The east corner of the tile is raised
-		SLOPE_N        = 0x08,                                  //!< The north corner of the tile is raised
-		SLOPE_STEEP    = 0x10,                                  //!< Indicates the slope is steep
+		SLOPE_W        = 1 << CORNER_W,                         //!< The west corner of the tile is raised
+		SLOPE_S        = 1 << CORNER_S,                         //!< The south corner of the tile is raised
+		SLOPE_E        = 1 << CORNER_E,                         //!< The east corner of the tile is raised
+		SLOPE_N        = 1 << CORNER_N,                         //!< The north corner of the tile is raised
+		SLOPE_STEEP    = 0x10,                                  //!< Indicates the slope is steep (The corner opposite of the not-raised corner is raised two times)
 		SLOPE_NW       = SLOPE_N | SLOPE_W,                     //!< North and west corner are raised
 		SLOPE_SW       = SLOPE_S | SLOPE_W,                     //!< South and west corner are raised
 		SLOPE_SE       = SLOPE_S | SLOPE_E,                     //!< South and east corner are raised
 		SLOPE_NE       = SLOPE_N | SLOPE_E,                     //!< North and east corner are raised
 		SLOPE_EW       = SLOPE_E | SLOPE_W,                     //!< East and west corner are raised
 		SLOPE_NS       = SLOPE_N | SLOPE_S,                     //!< North and south corner are raised
-		SLOPE_ELEVATED = SLOPE_N | SLOPE_E | SLOPE_S | SLOPE_W, //!< All corner are raised, similar to SLOPE_FLAT
+		SLOPE_ELEVATED = SLOPE_N | SLOPE_E | SLOPE_S | SLOPE_W, //!< Bit mask containing all 'simple' slopes. Does not appear as a slope.
 		SLOPE_NWS      = SLOPE_N | SLOPE_W | SLOPE_S,           //!< North, west and south corner are raised
 		SLOPE_WSE      = SLOPE_W | SLOPE_S | SLOPE_E,           //!< West, south and east corner are raised
 		SLOPE_SEN      = SLOPE_S | SLOPE_E | SLOPE_N,           //!< South, east and north corner are raised
@@ -129,6 +141,7 @@ public:
 
 	/**
 	 * Check if a tile has a steep slope.
+	 * Steep slopes are slopes with a height difference of 2 across one diagonal of the tile.
 	 * @param slope The slope to check on.
 	 * @pre slope != SLOPE_INVALID.
 	 * @return True if the slope is a steep slope.
@@ -137,9 +150,11 @@ public:
 
 	/**
 	 * Check if a tile has a halftile slope.
+	 * Halftile slopes appear on top of halftile foundations. E.g. the slope you get when building a horizontal railtrack on the top of a SLOPE_N or SLOPE_STEEP_N.
 	 * @param slope The slope to check on.
 	 * @pre slope != SLOPE_INVALID.
 	 * @return True if the slope is a halftile slope.
+	 * @note Currently there is no API function that would return or accept a halftile slope.
 	 */
 	static bool IsHalftileSlope(Slope slope);
 
@@ -193,9 +208,10 @@ public:
 
 	/**
 	 * Get the slope of a tile.
+	 * This is the slope of the bare tile. A possible foundation on the tile does not influence this slope.
 	 * @param tile The tile to check on.
 	 * @pre AIMap::IsValidTile(tile).
-	 * @return 0 means flat, others indicate internal state of slope.
+	 * @return Bit mask encoding the slope. See #Slope for a description of the returned values.
 	 */
 	static Slope GetSlope(TileIndex tile);
 
@@ -211,14 +227,44 @@ public:
 	static Slope GetComplementSlope(Slope slope);
 
 	/**
-	 * Get the height of the tile.
+	 * Get the height of the north corner of a tile.
+	 * The returned height is the height of the bare tile. A possible foundation on the tile does not influence this height.
+	 * @deprecated This function is deprecated and might be removed in future versions of the API. Use GetMinHeight(), GetMaxHeight() or GetCornerHeight() instead.
 	 * @param tile The tile to check on.
 	 * @pre AIMap::IsValidTile(tile).
-	 * @return The height of the tile, ranging from 0 to 15.
+	 * @return The height of the north corner of the tile, ranging from 0 to 15.
 	 */
 	static int32 GetHeight(TileIndex tile);
 
 	/**
+	 * Get the minimal height on a tile.
+	 * The returned height is the height of the bare tile. A possible foundation on the tile does not influence this height.
+	 * @param tile The tile to check on.
+	 * @pre AIMap::IsValidTile(tile).
+	 * @return The height of the lowest corner of the tile, ranging from 0 to 15.
+	 */
+	static int32 GetMinHeight(TileIndex tile);
+
+	/**
+	 * Get the maximal height on a tile.
+	 * The returned height is the height of the bare tile. A possible foundation on the tile does not influence this height.
+	 * @param tile The tile to check on.
+	 * @pre AIMap::IsValidTile(tile).
+	 * @return The height of the highest corner of the tile, ranging from 0 to 15.
+	 */
+	static int32 GetMaxHeight(TileIndex tile);
+
+	/**
+	 * Get the height of a certain corner of a tile.
+	 * The returned height is the height of the bare tile. A possible foundation on the tile does not influence this height.
+	 * @param tile The tile to check on.
+	 * @param corner The corner to query.
+	 * @pre AIMap::IsValidTile(tile).
+	 * @return The height of the lowest corner of the tile, ranging from 0 to 15.
+	 */
+	static int32 GetCornerHeight(TileIndex tile, Corner corner);
+
+	/**
 	 * Get the owner of the tile.
 	 * @param tile The tile to get the owner from.
 	 * @pre AIMap::IsValidTile(tile).
diff --git a/src/ai/api/ai_tile.hpp.sq b/src/ai/api/ai_tile.hpp.sq
index 8f9e83317..481cb68f9 100644
--- a/src/ai/api/ai_tile.hpp.sq
+++ b/src/ai/api/ai_tile.hpp.sq
@@ -7,6 +7,8 @@ namespace SQConvert {
 	/* Allow enums to be used as Squirrel parameters */
 	template <> AITile::ErrorMessages GetParam(ForceType<AITile::ErrorMessages>, HSQUIRRELVM vm, int index, SQAutoFreePointers *ptr) { SQInteger tmp; sq_getinteger(vm, index, &tmp); return (AITile::ErrorMessages)tmp; }
 	template <> int Return<AITile::ErrorMessages>(HSQUIRRELVM vm, AITile::ErrorMessages res) { sq_pushinteger(vm, (int32)res); return 1; }
+	template <> AITile::Corner GetParam(ForceType<AITile::Corner>, HSQUIRRELVM vm, int index, SQAutoFreePointers *ptr) { SQInteger tmp; sq_getinteger(vm, index, &tmp); return (AITile::Corner)tmp; }
+	template <> int Return<AITile::Corner>(HSQUIRRELVM vm, AITile::Corner res) { sq_pushinteger(vm, (int32)res); return 1; }
 	template <> AITile::Slope GetParam(ForceType<AITile::Slope>, HSQUIRRELVM vm, int index, SQAutoFreePointers *ptr) { SQInteger tmp; sq_getinteger(vm, index, &tmp); return (AITile::Slope)tmp; }
 	template <> int Return<AITile::Slope>(HSQUIRRELVM vm, AITile::Slope res) { sq_pushinteger(vm, (int32)res); return 1; }
 	template <> AITile::TransportType GetParam(ForceType<AITile::TransportType>, HSQUIRRELVM vm, int index, SQAutoFreePointers *ptr) { SQInteger tmp; sq_getinteger(vm, index, &tmp); return (AITile::TransportType)tmp; }
@@ -28,6 +30,11 @@ void SQAITile_Register(Squirrel *engine) {
 	SQAITile.DefSQConst(engine, AITile::ERR_TILE_BASE,     "ERR_TILE_BASE");
 	SQAITile.DefSQConst(engine, AITile::ERR_TILE_TOO_HIGH, "ERR_TILE_TOO_HIGH");
 	SQAITile.DefSQConst(engine, AITile::ERR_TILE_TOO_LOW,  "ERR_TILE_TOO_LOW");
+	SQAITile.DefSQConst(engine, AITile::CORNER_W,          "CORNER_W");
+	SQAITile.DefSQConst(engine, AITile::CORNER_S,          "CORNER_S");
+	SQAITile.DefSQConst(engine, AITile::CORNER_E,          "CORNER_E");
+	SQAITile.DefSQConst(engine, AITile::CORNER_N,          "CORNER_N");
+	SQAITile.DefSQConst(engine, AITile::CORNER_INVALID,    "CORNER_INVALID");
 	SQAITile.DefSQConst(engine, AITile::SLOPE_FLAT,        "SLOPE_FLAT");
 	SQAITile.DefSQConst(engine, AITile::SLOPE_W,           "SLOPE_W");
 	SQAITile.DefSQConst(engine, AITile::SLOPE_S,           "SLOPE_S");
@@ -78,6 +85,9 @@ void SQAITile_Register(Squirrel *engine) {
 	SQAITile.DefSQStaticMethod(engine, &AITile::GetSlope,                   "GetSlope",                   2, ".i");
 	SQAITile.DefSQStaticMethod(engine, &AITile::GetComplementSlope,         "GetComplementSlope",         2, ".i");
 	SQAITile.DefSQStaticMethod(engine, &AITile::GetHeight,                  "GetHeight",                  2, ".i");
+	SQAITile.DefSQStaticMethod(engine, &AITile::GetMinHeight,               "GetMinHeight",               2, ".i");
+	SQAITile.DefSQStaticMethod(engine, &AITile::GetMaxHeight,               "GetMaxHeight",               2, ".i");
+	SQAITile.DefSQStaticMethod(engine, &AITile::GetCornerHeight,            "GetCornerHeight",            3, ".ii");
 	SQAITile.DefSQStaticMethod(engine, &AITile::GetOwner,                   "GetOwner",                   2, ".i");
 	SQAITile.DefSQStaticMethod(engine, &AITile::HasTransportType,           "HasTransportType",           3, ".ii");
 	SQAITile.DefSQStaticMethod(engine, &AITile::GetCargoAcceptance,         "GetCargoAcceptance",         6, ".iiiii");
diff --git a/src/slope_type.h b/src/slope_type.h
index 2ba12bf38..469fd75b9 100644
--- a/src/slope_type.h
+++ b/src/slope_type.h
@@ -53,7 +53,7 @@ enum Slope {
 	SLOPE_NE       = SLOPE_N | SLOPE_E,                     ///< north and east corner are raised
 	SLOPE_EW       = SLOPE_E | SLOPE_W,                     ///< east and west corner are raised
 	SLOPE_NS       = SLOPE_N | SLOPE_S,                     ///< north and south corner are raised
-	SLOPE_ELEVATED = SLOPE_N | SLOPE_E | SLOPE_S | SLOPE_W, ///< all corner are raised, similar to SLOPE_FLAT
+	SLOPE_ELEVATED = SLOPE_N | SLOPE_E | SLOPE_S | SLOPE_W, ///< bit mask containing all 'simple' slopes
 	SLOPE_NWS      = SLOPE_N | SLOPE_W | SLOPE_S,           ///< north, west and south corner are raised
 	SLOPE_WSE      = SLOPE_W | SLOPE_S | SLOPE_E,           ///< west, south and east corner are raised
 	SLOPE_SEN      = SLOPE_S | SLOPE_E | SLOPE_N,           ///< south, east and north corner are raised