Get position of another node in local coordinates

green_manalishi

I apologize for bringing this up again :), but

How do I translate another node's coordinates to local coordinates?

This works, AFAIK, although only if the nodes are not rotated

var player_global = global.player.get_global_pos() var self_global = self.get_global_pos() var player_local = player_global - self_global

This is my attempt at doing the same using transforms. Wrong.

var player_global = global.player.get_global_pos() var self_gtrans = self.get_global_transform() var player_local = self_gtrans.xform(player_global)

Please, what's the correct way of doing this?

green_manalishi

This is a bit better as it works for rotated nodes, but if the 'self' node is scaled it's still wrong,

var player_global = global.player.get_global_pos() var self_gtrans = self.get_global_transform() var player_local = self_gtrans.xform_inv(player_global)

Sakaki

I think that if you actually want to translate it to 3D, you should use get_global_transform().origin

green_manalishi

I do not wan't to translate it to 3D. I want to translate the global coordinates of an arbitrary node (with any translation) to local coordinates of a node (with any translation).

Ross

The xform_inv() version should work, but scaling messes it up? That's weird. I mean, scaling a node normally changes the positions of all its children, but it doesn't do that?

green_manalishi

I'll try to explain my scaling issue: Let's say I use the above code to have an 'enemy' node (purple in the image) know the position of the 'player' node in it's local space. I test this by having the 'enemy' node draw a line between its own 0,0 position and the player's position (in local coordinates). A long as the 'enemy' isn't scaled it works (no matter the relative positions/rotations) of the two nodes, but if the 'enemy' node is scaled that isn't compensated for by this method. That means, if the 'enemy' is scaled 2x the line will continue through it.

Does this mean that scaling a node (the 'enemy' node) does affect how it is drawn, but doesn't actually affect the node's local coordinate system? Or does it mean I understand even less of vector math than I first thought? I didn't think that was possible...

edit: enemy code for good measure extends Sprite onready var player = get_parent().get_node("player") func _draw(): -- var ppos = player.get_global_pos() -- var self_gtrans = self.get_global_transform() -- var p_local = self_gtrans.xform_inv(ppos) -- draw_line(Vector2(0,0), p_local, Color("#ffff00"), 2)

Ross

OK, it looks like might be some weirdness with _draw(), check this out: https://github.com/godotengine/godot/issues/5428

green_manalishi

OK I'll need some time to understand what's going on in that thread... but it's comforting to know that it's not just me being dense.