Geometry.is_polygon_clockwise seems to return the opposite of expected results

[davidscholberg]

Godot version

v3.3.2.stable.official

System information

Windows 10, GLES3, GeForce GTX 1070/PCIe/SSE2

Issue description

The results of Geometry.is_polygon_clockwise seem consistent with a cartesian coordinate system where the Y axis grows upwards. However, I was under the impression that 2D graphics in Godot used a coordinate system where the Y axis grows downward, and since Geometry.is_polygon_clockwise is an inherently 2D function, the results given seem to be the opposite of what I would have expected.

Steps to reproduce

1. Add the following line to any node script and observe that the output is True, which is not consistent with the 2D coordinate system that Godot uses with the Y axis growing downward.

print(str(Geometry.is_polygon_clockwise(PoolVector2Array([Vector2(-1, -1), Vector2(-1, 1), Vector2(1, 1), Vector2(1, -1)]))))

Minimal reproduction project

No response

[Calinou]

cc @Xrayez

[Xrayez]

It looks like a bug to me. I have previously exposed this method to scripting in #28987, but I never really paid attention to result because nowadays I'm calculating polygon's signed area to determine the orientation in my code.

See also #30251 which can be added as an alternative to is_polygon_clockwise(), because orientation could be computed via area alone, and computing area will be more useful for other stuff, so we could remove is_polygon_clockwise() in Godot 4.0:

var clockwise = Geometry.polygon_area(polygon) < 0           # aka Hole
var counter_clockwise = Geometry.polygon_area(polygon) > 0   # aka Boundary

See also #53574 (comment).

[markopolojorgensen]

Just ran into this issue using godot 4.0.1. If is_polygon_clockwise is going to remain accessible via script, would it be better to change what it's returning or update documentation to let users know? I understand if it's low priority, seems like it's only affected three or four people in ~2 years.