Fix hover tanks thinking they are submarines, going under the water, …

…and the height wrapping around.

Hover tanks float above the water, which can only be fixed when droid heights are stored in something slightly less unsigned.
Closes ticket:1554 which was a combination of bugs or design flaws exposed in -r9619.

git-svn-id: https://warzone2100.svn.sourceforge.net/svnroot/warzone2100/trunk@9741 4a71c877-e1ca-e34f-864e-861f7616d084

Backport of be907e3, fixes #2232.

src/droid.c

@@ -4446,8 +4446,8 @@ BOOL isVtolDroid(const DROID* psDroid)
 	    && psDroid->droidType != DROID_TRANSPORTER;
 }
 
-/* returns true if the droid has lift propulsion and is moving */ 
-BOOL isFlying(const DROID* psDroid) 
+// returns true if the droid has lift propulsion and is moving
+BOOL isFlying(const DROID* psDroid)
 { 
 	return (asPropulsionStats + psDroid->asBits[COMP_PROPULSION].nStat)->propulsionType == PROPULSION_TYPE_LIFT  
 			&& ( psDroid->sMove.Status != MOVEINACTIVE || psDroid->droidType == DROID_TRANSPORTER ); 

src/map.c

@@ -865,13 +865,12 @@ BOOL mapLoad(char *filename)
 	{
 		for (j=0;j<mapHeight;j++)
 		{
-			setTileHeight(i, j, map_TileHeight(i, j));
 			// FIXME: magic number
 			mapTile(i, j)->waterLevel = mapTile(i, j)->height - world_coord(1) / 3.0f / (float)ELEVATION_SCALE;
 			// lower riverbed
 			if (mapTile(i, j)->ground == waterGroundType)
 			{
-				mapTile(i, j)->height = mapTile(i, j)->height - (WATER_DEPTH - 2.0f * environGetData(i, j)) / (float)ELEVATION_SCALE;
+				mapTile(i, j)->height -= (WATER_DEPTH - 2.0f * environGetData(i, j)) / (float)ELEVATION_SCALE;
 			}
 		}
 	}
@@ -1964,7 +1963,7 @@ BOOL map_Intersect(int* Cx, int* Cy, int* Vx, int* Vy, int* Sx, int* Sy)
 	return false;
 }
 
-/// The height of the terrain at the specified world coordinates
+/// The max height of the terrain and water at the specified world coordinates
 extern SWORD map_Height(int x, int y)
 {
 	int tileX, tileY;
@@ -1999,7 +1998,7 @@ extern SWORD map_Height(int x, int y)
 	{
 		for (j = 0; j < 2; j++)
 		{
-			height[i][j] = map_TileHeight(tileX+i, tileY+j);
+			height[i][j] = map_TileHeightSurface(tileX+i, tileY+j);
 			center += height[i][j];
 		}
 	}
@@ -2062,22 +2061,24 @@ extern SWORD map_Height(int x, int y)
 	onBottom = left * (1 - towardsRight) + right * towardsRight;
 	result = onBottom + (center - middle) * towardsCenter * 2;
 
+	result = MAX(result, 0);  // HACK Avoid unsigned underflow, when this is squashed into a Vector3uw later.
 	return (SDWORD)(result+0.5f);
 }
 
 /* returns true if object is above ground */
 extern BOOL mapObjIsAboveGround( BASE_OBJECT *psObj )
 {
 	// min is used to make sure we don't go over array bounds!
+	// TODO Using the corner of the map instead doesn't make sense. Fix this...
 	SDWORD	iZ,
 			tileX = map_coord(psObj->pos.x),
 			tileY = map_coord(psObj->pos.y),
 			tileYOffset1 = (tileY * mapWidth),
 			tileYOffset2 = ((tileY+1) * mapWidth),
-			h1 = psMapTiles[MIN(mapWidth * mapHeight, tileYOffset1 + tileX)    ].height * ELEVATION_SCALE,
-			h2 = psMapTiles[MIN(mapWidth * mapHeight, tileYOffset1 + tileX + 1)].height * ELEVATION_SCALE,
-			h3 = psMapTiles[MIN(mapWidth * mapHeight, tileYOffset2 + tileX)    ].height * ELEVATION_SCALE,
-			h4 = psMapTiles[MIN(mapWidth * mapHeight, tileYOffset2 + tileX + 1)].height * ELEVATION_SCALE;
+			h1 = psMapTiles[MIN(mapWidth * mapHeight - 1, tileYOffset1 + tileX)    ].height * ELEVATION_SCALE,
+			h2 = psMapTiles[MIN(mapWidth * mapHeight - 1, tileYOffset1 + tileX + 1)].height * ELEVATION_SCALE,
+			h3 = psMapTiles[MIN(mapWidth * mapHeight - 1, tileYOffset2 + tileX)    ].height * ELEVATION_SCALE,
+			h4 = psMapTiles[MIN(mapWidth * mapHeight - 1, tileYOffset2 + tileX + 1)].height * ELEVATION_SCALE;
 
 	/* trivial test above */
 	if ( (psObj->pos.z > h1) && (psObj->pos.z > h2) &&

src/map.h

@@ -318,24 +318,34 @@ static inline WZ_DECL_PURE MAPTILE *mapTile(SDWORD x, SDWORD y)
 	return &psMapTiles[x + (y * mapWidth)];
 }
 
-/* Return height of tile at x,y */
+/// Return ground height of top-left corner of tile at x,y
 static inline WZ_DECL_PURE float map_TileHeight(UDWORD x, UDWORD y)
 {
 	if ( x >= mapWidth || y >= mapHeight )
 	{
 		return 0;
 	}
-	return ((float)psMapTiles[x + (y * mapWidth)].height * ELEVATION_SCALE);
+	return psMapTiles[x + (y * mapWidth)].height * ELEVATION_SCALE;
 }
 
-/* Return height of tile at x,y */
+/// Return water height of top-left corner of tile at x,y
 static inline WZ_DECL_PURE float map_WaterHeight(UDWORD x, UDWORD y)
 {
 	if ( x >= mapWidth || y >= mapHeight )
 	{
 		return 0;
 	}
-	return ((float)psMapTiles[x + (y * mapWidth)].waterLevel * ELEVATION_SCALE);
+	return psMapTiles[x + (y * mapWidth)].waterLevel * ELEVATION_SCALE;
+}
+
+/// Return max(ground, water) height of top-left corner of tile at x,y
+static inline WZ_DECL_PURE float map_TileHeightSurface(SDWORD x, SDWORD y)
+{
+	if ( x >= mapWidth || y >= mapHeight )
+	{
+		return 0;
+	}
+	return MAX(psMapTiles[x + (y * mapWidth)].height, psMapTiles[x + (y * mapWidth)].waterLevel) * ELEVATION_SCALE;
 }
 
 
@@ -401,7 +411,7 @@ typedef struct _tile_coord
 /* Intersect a line with the map and report tile intersection points */
 extern BOOL map_Intersect(int *Cx, int *Cy, int *Vx, int* Vy, int *Sx, int *Sy);
 
-/* Return height of x,y */
+/// The max height of the terrain and water at the specified world coordinates
 extern SWORD map_Height(int x, int y);
 
 /* returns true if object is above ground */