- Steam or GOG
- Steam
- Single Player/Multiplayer
- Both
- Operating System
- Windows 11
- Terraria Version
- 1.4.4.9
- Controls Used
- Keyboard/Mouse
when determining whether player is in underground desert biome, the game compares the surface height with the player's Y coordinate. However, the surface height is measured in tiles, while the player's coordinate is mesured in pixels. since each tile is 16-pixel high, the player is almost always considered "underground" in this test.
Here is a example, in this map, the surface area is 1306/2 (from depth meter) + 3 (player height) + 41 (tiles outside the top of the screen) = 697 tiles high. when player stands on the top of the world (the 44-th block), its center is at 44 * 16 - 22 (half the player height) = 682 pixels. and since 682 < 697 the player is considered not in underground desert here. thus the NPC spawn cap is at the default value (5), no matter how long you wait only 5 harpies can spawn simultaneously
However if the player step down one tile, it becomes 682 + 16 = 698 > 697 pixels away from the top edge, the player is then considered in underground desert (with desert biome and sandstone wall on back), as a result, it receive the underground desert spawn rate and max spawn multiplier and the NPC spawn cap is increased to 15.
Due to the fact that player is not allowed to enter the top 41 tiles of the map, it requires at least 697-tile-high surface area to observe this phenomenom, which is only possible in a few large drunk worlds (where the world height is more varied), in most of the worlds the boundary is outside the top of the screen so that ALL the space and surface area are treated as underground when checking underground desert biome.
Here is a example, in this map, the surface area is 1306/2 (from depth meter) + 3 (player height) + 41 (tiles outside the top of the screen) = 697 tiles high. when player stands on the top of the world (the 44-th block), its center is at 44 * 16 - 22 (half the player height) = 682 pixels. and since 682 < 697 the player is considered not in underground desert here. thus the NPC spawn cap is at the default value (5), no matter how long you wait only 5 harpies can spawn simultaneously
However if the player step down one tile, it becomes 682 + 16 = 698 > 697 pixels away from the top edge, the player is then considered in underground desert (with desert biome and sandstone wall on back), as a result, it receive the underground desert spawn rate and max spawn multiplier and the NPC spawn cap is increased to 15.
Due to the fact that player is not allowed to enter the top 41 tiles of the map, it requires at least 697-tile-high surface area to observe this phenomenom, which is only possible in a few large drunk worlds (where the world height is more varied), in most of the worlds the boundary is outside the top of the screen so that ALL the space and surface area are treated as underground when checking underground desert biome.