Changing CSG node Snap doesn't regenerate mesh

[31]

Tested versions

• Add csg boolean operators using elalish/manifold. #91748 (df33cbf)
• Godot v4.2.2.stable

System information

Godot v4.2.2.stable - Windows 10.0.22631 - Vulkan (Forward+)

Issue description

I found this on a build of #91748, but it applies to 4.2.2 as well and the code is the same on tip.

I tried running TextMesh through CSGMesh3D and subtracting it from a box (Text.tscn) as a way to generate situations where CSG meshing might have problems without making a bunch of nodes or making a big mesh of my own. I spotted some bumpy triangles:

Changing the Box's Snap from 0.001 to 0.0001 and reloading the scene fixes it:

But: should I really need to reload the scene? Or should set_snap include _make_dirty(); like the other methods do?

godot/modules/csg/csg_shape.cpp

Lines 143 to 145 in 71699e0

	void CSGShape3D::set_snap(float p_snap) {
	snap = p_snap;
	}

godot/modules/csg/csg_shape.cpp

Lines 628 to 632 in 71699e0

	void CSGShape3D::set_operation(Operation p_operation) {
	operation = p_operation;
	_make_dirty();
	update_gizmos();
	}

I can imagine someone seeing this problem, not knowing to reload the scene (or jiggle a node) and thinking that Snap is broken! With the improvements to CSG in #91748, this might interfere with users attempting to try out the feature and make them think it's less capable than it is.

---

On 4.2.2, 0.001 snap looks worse, and the mesh has holes (a known issue across many scenarios):

Changing to 0.0001 snap doesn't look quite as good as #91748, but it is an improvement in this part of the mesh as there are no visible holes:

(There are plenty of holes elsewhere in the mesh, but I think that's to be expected.)

Steps to reproduce

1. Load https://gist.github.com/31/c3c4bace42d4ca550ae6badf0f2b7cf9, or make a CSG scene with problems that need a lower snap value.
2. Change snap.
3. See that the generated mesh doesn't change.

Minimal reproduction project (MRP)

Text.tscn: https://gist.github.com/31/c3c4bace42d4ca550ae6badf0f2b7cf9