CSG: Resizing shapes using opposite side instead of center

[mrzapp]

Godot version:
3.1-dev

Issue description:
When resizing a CSG shape (or any shape, probably), the resizing is done from the center on the chosen axis, forcing us to move the Spatial node for every adjustment to the shape. Also mentioned here

Solution:
I propose that, when holding down a modifier key, the shape is resized using the opposite side as an anchor rather than the center.

[CptPotato]

What exactly do you mean by 'opposite' side?

[nodefish]

Resizing a CSG Shape (or even things like collision shape extents) expands/shrinks both sides from the center of the shape. This makes it very hard to judge the resulting size, and very often you have to re-adjust the position of the shape after doing it.

It would be much easier to work with if you could resize non-symmetrically, in 1 direction only, e.g. in the case of a cube, moving a single face like so: https://imgur.com/a/Gyqm6OL

This is what is meant by "using the opposite side as an anchor," e.g. if I'd like to expand in the +Z direction, the shape should not expand in the -Z direction.

(The above recording is using a simple tool I wrote in GDscript to make it faster and less finicky to resize CSG shapes. I'll gladly share it if someone asks but I think it's so simple nobody will want it).

[mrzapp]

@nodefish Please go ahead and share it, I don't see how it couldn't be helpful.

And thanks for supplementing with your explanation, it was a lot more precise than mine.

[nodefish]

csg-widget.zip

The idea is to make instances of this basic EditableCSG scene and enable "editable children" to build prefabs etc.

However, if you instance it into a complex scene, it becomes a bit difficult to click and drag the widgets due to 3D selection issues (#6867).

[Calinou]

Closing in favor of godotengine/godot-proposals#452, as feature proposals are now tracked on the Godot proposals repository.