Very small nodeboxes z-fighting with overlay tile of neighboring node

[kno10]

Luanti version

Luanti 5.11.0-dev-9eac0126b (Linux)
Using LuaJIT 2.1.1723681758 (OpenResty)
Built by GCC 14.2
Running on Linux/6.11.6 x86_64
BUILD_TYPE=Release
RUN_IN_PLACE=0
USE_CURL=1
USE_GETTEXT=1
USE_SOUND=1
STATIC_SHAREDIR="/usr/local/share/luanti"
STATIC_LOCALEDIR="/usr/local/share/locale"

Note: SDL disabled, because of its horrible input lag.

Operating system and version

Debian sid

CPU model

Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz

GPU model

Intel Corporation UHD Graphics 620 (rev 07)

Active renderer

Irrlicht (4.6 / opengl3 / X11)

Summary

With current HEAD:

With 5.10 release:

Notice how pink petals textures are cut off based on distance. Possibly due to some z-fighting, so that the petals disappear after a certain distance.

Steps to reproduce

Probably affects any node with a texture at -7.9/16, so rather close to the node below.

[Desour]

What are the node defs for these nodes? Are the petals separate nodes?

---

Possibly related: #15634

[sfan5]

I can't find the revision "9eac0126b" anywhere. If your build is older than 4774e65 you should update first.

[kno10]

It is #15027 rebased on 464cc92 (which is master yesterday).
So 4774e65 is included.

Node definition is here: https://git.minetest.land/VoxeLibre/VoxeLibre/src/commit/d0dd2bc13738b1f7e21800435898604443820c9f/mods/ITEMS/mcl_cherry_blossom/nodes.lua#L105-L117

        drawtype = "nodebox",
	node_box = {type = "fixed", fixed = {-1/2, -1/2, -1/2, 1/2, -7.9/16, 1/2}},

to test, you should be able to download https://git.minetest.land/VoxeLibre/VoxeLibre/archive/mapgen-test-branch.tar.gz
and use /findbiome CherryGrove.

[sfan5]

This is actually a regression from 5b14c03 and does not interact with #15531 at all.

This happens when rendering the overlay tiles of grass, since the bias is high enough that it intersects with the petals.
I tried some different values for PolygonOffsetSlopeScale but there's none that fixes both the grass z-fighting and petals.
Unless some magic solution pops up I think you will have to live with the fact that 0.00625 is not enough leeway for the engine to apply other overlays problem-free, and adjust the nodebox.