Geometry.offset_polyline_2d polygon not behaving as expected

enriktigstad

Hi, I'm having a trouble with the resulting polygon from Geometry.offset_polyline_2d not lining up with the line geometry passed to the function.

What I'm trying to achieve is creating a navigation polygon from a line that I've drawn in the editor.

This is my code:

extends Navigation2D

onready var RoadLine: Line2D = $RoadLine
onready var NavigationPoly: NavigationPolygonInstance = $NavigationPolygonInstance
#onready var DrawPolygon: Polygon2D = $Polygon2D


func _ready():
	var buffered_line = Geometry.offset_polyline_2d(RoadLine.points, 10)

#	DrawPolygon.polygon = buffered_line[0]
	var polygon = NavigationPolygon.new()
	polygon.add_outline(buffered_line[0])
	polygon.make_polygons_from_outlines()
	NavigationPoly.position = RoadLine.position
	NavigationPoly.navpoly = polygon
	
	print('ready')

Scene tree:

And this is the result, purple line is RoadLine and the green polygon is NavigationPolygon with debug option visible navigation turned on: Buffered line

My expectation was the the polygon would nicely line up with the line, like running a buffer operation in a GIS program, example from PostGIS below:

Am I doing something wrong or is the function not behaving as it should? (I assume it's on my end).

Geometry.offset_polyline_2d documentation

cybereality

It works for me. I copied your code exactly with no changes.

enriktigstad

Ok! Interesting, what Godot version are you on?

cybereality

3.4

enriktigstad

Ok, I just tried it in a blank project and it works fine. So might be something in my project settings in the original project?

enriktigstad

Found it! Turns out I had messed with the scaling of the Line2D by dragging the handles in the editor. That will scale how the line is drawn to the screen, but the line coordinates will still be the same.