Allow triangulation starting at 2nd vertex

[MarioLiebisch]

While the difference is neglectable in many cases, this is most noticeable when triangulating quads, as this allows you to switch the diagonal you want to create (from first to third vertex or from second to fourth).

By default, when triangulating quads, you'd always get this diagonal:

However, in some cases you might prefer to triangulate in the other direction, e.g. to block out some specific diagonal/geometry.

To achieve this, the new, smaller +1 button will essentially offset the triangulation by 1, moving the first vertex per face to the end:

There might be a better way to do this – or maybe it's even included and I haven't found it yet, but I wanted to try this to block out a test level (or even more). Let me know what you think or if I indeed missed something obvious!

[fire]

I think instead of +1 you can use something visual that represent flipping. The feature is good though.

[MarioLiebisch]

Yep, couldn't come up with something creative, though. Maybe mirroring the original icon? I'm not sure. Especially considering it wouldn't always just mirror the splitting.

[jarneson]

Suggested change

	var v = verts[0]
	verts.remove_at(0)
	verts.push_back(v)
	verts.push_back(verts.pop_front())

[MarioLiebisch]

Yeah, true. Thought there wouldn't be a pop_front(), but guess I remembered that one wrong.👍

[jarneson]

additionally, just having a +1 button doesn't really work for anything with more edges than a quad (or maybe even rectangle?), since this uses ear clipping to attempt to triangulate somewhat reasonably, and doesn't work particularly well for multiselect (although the current algorithm doesn't do a great job to begin with!)

i wonder if a better feature is to just have an edge cut tool -- select two verts and add an edge between them if they lie on the same face.

[MarioLiebisch]

Yeah, I also thought about removing the button and making it a shortcut (like holding Ctrl), but splitting edges might indeed be the way more obvious and useful addition.

[jarneson]

If you are interested in chasing edge creation, sfme in euler.gd should work out of the box: https://github.com/jarneson/godot-ply/blob/main/addons/ply/resources/euler.gd#L61

[fire]

This doesn't look like it is complete yet.