FindSpawnPos: Let mapgens decide what spawn altitude is suitable

To avoid spawn search failing in new specialised mapgens
Increase spawn search range to 4000 nodes
Add getSpawnLevelAtPoint() functions to EmergeManager, class Mapgen
and all mapgens
Remove getGroundLevelAtPoint() functions from all mapgens except mgv6
(possibly to be re-added later in the correct form to return actual
ground level)
Make mgvalleys flag names consistent with other mapgens
Remove now unused 'vertical spawn range' setting

1 files changed, 14 insertions, 13 deletions

diff --git a/src/mapgen_v5.cpp b/src/mapgen_v5.cpp
index 06e5f1ca6..0bb3715a8 100644
--- a/src/mapgen_v5.cpp
+++ b/src/mapgen_v5.cpp
@@ -171,7 +171,7 @@ void MapgenV5Params::writeParams(Settings *settings) const
 }
 
 
-int MapgenV5::getGroundLevelAtPoint(v2s16 p)
+int MapgenV5::getSpawnLevelAtPoint(v2s16 p)
 {
 	//TimeTaker t("getGroundLevelAtPoint", NULL, PRECISION_MICRO);
 
@@ -182,24 +182,25 @@ int MapgenV5::getGroundLevelAtPoint(v2s16 p)
 		f *= 1.6;
 	float h = NoisePerlin2D(&noise_height->np, p.X, p.Y, seed);
 
-	s16 search_start = 128; // Only bother searching this range, actual
-	s16 search_end = -128;  // ground level is rarely higher or lower.
-
-	for (s16 y = search_start; y >= search_end; y--) {
+	for (s16 y = 128; y >= -128; y--) {
 		float n_ground = NoisePerlin3D(&noise_ground->np, p.X, y, p.Y, seed);
-		// If solid
-		if (n_ground * f > y - h) {
+
+		if (n_ground * f > y - h) {  // If solid
 			// If either top 2 nodes of search are solid this is inside a
-			// mountain or floatland with no space for the player to spawn.
-			if (y >= search_start - 1)
-				return MAX_MAP_GENERATION_LIMIT;
-			else
-				return y; // Ground below at least 2 nodes of space
+			// mountain or floatland with possibly no space for the player to spawn.
+			if (y >= 127) {
+				return MAX_MAP_GENERATION_LIMIT;  // Unsuitable spawn point
+			} else {  // Ground below at least 2 nodes of empty space
+				if (y <= water_level || y > water_level + 16)
+					return MAX_MAP_GENERATION_LIMIT;  // Unsuitable spawn point
+				else
+					return y;
+			}
 		}
 	}
 
 	//printf("getGroundLevelAtPoint: %dus\n", t.stop());
-	return -MAX_MAP_GENERATION_LIMIT;
+	return MAX_MAP_GENERATION_LIMIT;  // Unsuitable spawn position, no ground found
 }