Occlusion culling no longer works following the Embree 4 upgrade when using builtin_embree=no

[Calinou]

Tested versions

• Reproducible in: 4.3.dev 029aade
• Not reproducible in: 4.2.1.stable, 4.3.dev5

System information

Godot v4.3.dev (029aade) - Fedora Linux 39 (KDE Plasma) - X11 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4090 (nvidia; 550.67) - 13th Gen Intel(R) Core(TM) i9-13900K (32 Threads)

Issue description

Occlusion culling no longer works following the Embree 4 upgrade. It doesn't seem to work in the Occlusion culling and mesh LOD demo either, even though it worked when I was testing the PR.

4.3.dev 5 (working)

4.3.dev 029aade (broken)

I bisected the regression to c43eab5 (#88783). cc @Chubercik

Steps to reproduce

• Open the MRP linked below.
• Switch to the Overdraw debug draw mode in the Perspective menu of the 3D viewport in the editor.
• Move around in the scene with freelook. Cubes behind the discs should disappear when they are occluded.

Minimal reproduction project (MRP)

test_occluder_runtime_bake.zip

[AeioMuch]

Can't reproduce on my side. It look like the first screenshot for me
Godot v4.3.dev (029aade) - Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3060 (NVIDIA; 31.0.15.5212) - Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz (8 Threads)

[Chubercik]

Can't reproduce on my side either, occlusion seems to be working as intended.

• Godot 4.3.dev6 (64520fe)
• Windows 10.0.19045
• Vulkan 1.3.277 (Forward+)
• dedicated NVIDIA GeForce GTX 1080 Ti (NVIDIA; 552.22)
• 7th Gen Intel(R) Core(TM) i7-7700K @ 4.20GHz (4 cores, 8 threads)

---

[Calinou]

It turns out what broke was builtin_embree=no, not Embree itself (builtin_embree=yes is the default). This option is designed to use dynamically linked Embree from system repositories (I use this to speed up linking times a bit). I have embree-devel-4.2.0 installed from the Fedora 39 repositories.

builtin_embree=yes makes the occlusion culling work again. Therefore, it appears the issue is that system Embree can no longer be used, even though the builtin_embree SCons option is still listed in scons --help.

[Chubercik]

Might've found the culprit:

godot/platform/linuxbsd/detect.py

Lines 310 to 312 in 55b8724

	if not env["builtin_embree"] and env["arch"] in ["x86_64", "arm64"]:
	# No pkgconfig file so far, hardcode expected lib name.
	env.Append(LIBS=["embree3"])

I don't have a setup to test it currently, but changing embree3 to embree4 (or maybe embree? judging by the Fedora packages website: embree3 vs embree4) should fix the issue.

[akien-mga]

Yes it should be embree4. But I'm surprised you get a surprisingly non working build, as opposed to a linking issue.