If I have a tilemap that is 4x8, positioned at 0,0 in the editor as follows:
What code would I use such that it ends up "centered" when my game runs?
I'm hoping for an end result that would look like this:
As you can see, the tilemap has been moved left 24 pixels and up 24 pixels. This example is manually done, but I'd like to be able to do it using the Godot APIs so that tilemaps of different dimensions can be centered.
My current answer makes the following assumptions about your TileSet:
move_layer().Different settings may require changing some formulas below to consider different layout orientations or topologies.
Before computing the centre of mass of the TileMap, we need to know its current extent:
var used_rect: Rect2 = get_used_rect() This describes where the top-leftmost cell is (via used_rect.position) and the size of the current map (via used_rect.size), in your case, 8x4. Now, we can work out the position of all corners in map space and convert them into TileMap local space:
var map_corners: Array = [ rect.position, rect.position + rect.size * Vector2.RIGHT, rect.position + rect.size * Vector2.DOWN, rect.position + rect.size ] var local_corners: Array = map_corners.map( func(v): return map_to_local(v)) However, we are counting an extra cell along each layout axis (I'm using a custom script for drawing. The Godot icon is at the (0,0) position for reference, and the blue dot is the top-leftmost corner of the layout):
We can fix this by subtracting one from each direction. After we get the used rectangle, and before computing the map_corners array, we do:
used_rect.size -= Vector2.ONE Now, everything is fine:
The centre of the TileMap is the average of the corner positions in local space. The following line uses reduce() to accumulate the sum of all corner coordinates, and finally divides it by their number to compute the mean position:
var local_centroid: Vector2 = local_corners.reduce( func(accum, corner): return accum + corner, Vector2.ZERO) / len(local_corners) This is indeed the centroid of the TileMap in local coordinates (red dot):
This turned out to be very easy. At first, I started thinking about inverse transforms and stuff... This line works perfectly and is independent of any Node hierarchy involved:
global_position = -centroid 
Here's the final class and the function to centre the TileMap:
extends TileMap func _ready() -> void: recentre() func recentre() -> void: var used_rect: Rect2 = get_used_rect() used_rect.size -= Vector2.ONE var map_corners: Array = [ rect.position, rect.position + rect.size * Vector2.RIGHT, rect.position + rect.size * Vector2.DOWN, rect.position + rect.size ] var local_corners: Array = map_corners.map( func(v): return map_to_local(v)) var local_centroid: Vector2 = local_corners.reduce( func(accum, corner): return accum + corner, Vector2.ZERO) / len(local_corners) global_position = -centroid 