Tile height set by lazy.

This is good enough to give a 10% performance boost for regular players when there are a lot of units.
If mods add elevation somehow WITHIN a turn, this will be lost, but will recalc next turn correctly.

core/src/com/unciv/logic/automation/UnitAutomation.kt

@@ -31,7 +31,7 @@ object UnitAutomation {
                 unit.movement.getDistanceToTiles().keys.filter { isGoodTileToExplore(unit, it) }
         if (explorableTilesThisTurn.any()) {
             val bestTile = explorableTilesThisTurn
-                .sortedByDescending { it.getHeight() }  // secondary sort is by 'how far can you see'
+                .sortedByDescending { it.height }  // secondary sort is by 'how far can you see'
                 .maxByOrNull { it.aerialDistanceTo(unit.currentTile) }!! // primary sort is by 'how far can you go'
             unit.movement.headTowards(bestTile)
             return true

core/src/com/unciv/logic/map/TileInfo.kt

@@ -157,12 +157,14 @@ open class TileInfo {
     // We have to .toList() so that the values are stored together once for caching,
     // and the toSequence so that aggregations (like neighbors.flatMap{it.units} don't take up their own space
 
-    fun getHeight(): Int {
-        return getAllTerrains().flatMap { it.uniqueObjects }
-            .filter { it.placeholderText == "Has an elevation of [] for visibility calculations" }
+    @delegate:Transient
+    val height : Int by lazy {
+        getAllTerrains().flatMap { it.uniqueObjects }
+            .filter { it.isOfType(UniqueType.VisibilityElevation) }
             .map { it.params[0].toInt() }.sum()
     }
 
+
     fun getBaseTerrain(): Terrain = baseTerrainObject
 
     fun getOwner(): CivilizationInfo? {

core/src/com/unciv/logic/map/TileMap.kt

@@ -280,7 +280,7 @@ class TileMap {
     /** @return List of tiles visible from location [position] for a unit with sight range [sightDistance] */
     fun getViewableTiles(position: Vector2, sightDistance: Int): List<TileInfo> {
         val viewableTiles = getTilesInDistance(position, 1).toMutableList()
-        val currentTileHeight = get(position).getHeight()
+        val currentTileHeight = get(position).height
 
         for (i in 1..sightDistance) { // in each layer,
             // This is so we don't use tiles in the same distance to "see over",
@@ -288,7 +288,7 @@ class TileMap {
             val tilesToAddInDistanceI = ArrayList<TileInfo>()
 
             for (cTile in getTilesAtDistance(position, i)) { // for each tile in that layer,
-                val cTileHeight = cTile.getHeight()
+                val cTileHeight = cTile.height
 
                 /*
             Okay so, if we're looking at a tile from a to c with b in the middle,
@@ -307,7 +307,7 @@ class TileMap {
 
                 val containsViewableNeighborThatCanSeeOver = cTile.neighbors.any {
                         bNeighbor: TileInfo ->
-                    val bNeighborHeight = bNeighbor.getHeight()
+                    val bNeighborHeight = bNeighbor.height
                     viewableTiles.contains(bNeighbor) && (
                             currentTileHeight > bNeighborHeight // a>b
                                     || cTileHeight > bNeighborHeight // c>b

core/src/com/unciv/models/ruleset/unique/UniqueType.kt

@@ -223,6 +223,7 @@ enum class UniqueType(val text:String, vararg targets: UniqueTarget) {
 
     TileProvidesYieldWithoutPopulation("Tile provides yield without assigned population", UniqueTarget.Terrain, UniqueTarget.Improvement),
     NullifyYields("Nullifies all other stats this tile provides", UniqueTarget.Terrain),
+    VisibilityElevation("Has an elevation of [amount] for visibility calculations", UniqueTarget.Terrain),
 
     NoNaturalGeneration("Doesn't generate naturally", UniqueTarget.Terrain),