Subject: [Linux/Proton] Grass LOD culling inverted based on camera pitch — Vulkan renderer
Platform: Linux (Arch/CachyOS), Steam Proton
Game: Ghost Recon Breakpoint (AppID 2231380)
Description
On Linux with the Vulkan renderer (via Steam Proton/Wine), grass meshes are culled
based on camera pitch in a way that is inverted from the expected behavior:
Windows (DX12/Vulkan): Camera looking forward → grass visible. Camera looking down →
grass culled (outside view frustum).
Linux (Vulkan/Proton): Camera looking forward → grass culled. Camera looking down →
grass visible.
This means grass is invisible when looking forward (the most common view) and only appears
when looking down. The inversion is consistent across all tested Proton versions
(8.0-5, 9.0-4, Experimental) and persists regardless of Gamescope usage.
This may be a frustum culling issue (camera view frustum check inverted) rather than an
LOD selection issue — the grass is completely hidden, not just rendered at lower detail.
Steps to Reproduce
Launch game on Linux with Vulkan renderer (default on Proton).
Stand in any open-world area with grass.
Look forward — grass is invisible/culled.
Look down at ~45° — grass appears.
Look up or forward again — grass disappears.
Expected Behavior
Grass should be visible when looking forward (within the camera view frustum) and culled
when looking down (outside the view frustum). This matches the behavior on Windows Vulkan.
Environment
OS: Arch Linux (CachyOS), Wayland/KDE
CPU: AMD Ryzen 9 5900XT (16C/32T)
GPU: AMD RX 9060 XT (RDNA4), Mesa 25.3.1
RAM: 32 GB DDR4 3600MHz
Proton: ProtonGE 11-1, Proton CachyOS (SLR and Native)
Gamescope: Present but persists without it
Kernel: 7.1.3-1-cachyos
Display: 2560×1080 200Hz HDR
Additional Notes
The bug is specific to Linux Vulkan (via Proton). Windows Vulkan does NOT exhibit
this bug — it's not a Vulkan renderer issue in the game engine itself.
Lowering GrassQuality in GRB.ini reduces grass density but does not fix the culling
inversion.
No other Proton/VKD3D game has been reported with this exact inverted culling behavior.
This appears to be a VKD3D-Proton translation layer issue affecting camera-perspective-
dependent frustum culling in the Anvil engine's Vulkan renderer path on Linux.
Subject: [Linux/Proton] Grass LOD culling inverted based on camera pitch — Vulkan renderer
Platform: Linux (Arch/CachyOS), Steam Proton
Game: Ghost Recon Breakpoint (AppID 2231380)
Description
On Linux with the Vulkan renderer (via Steam Proton/Wine), grass meshes are culled
based on camera pitch in a way that is inverted from the expected behavior:
grass culled (outside view frustum).
grass visible.
This means grass is invisible when looking forward (the most common view) and only appears
when looking down. The inversion is consistent across all tested Proton versions
(8.0-5, 9.0-4, Experimental) and persists regardless of Gamescope usage.
This may be a frustum culling issue (camera view frustum check inverted) rather than an
LOD selection issue — the grass is completely hidden, not just rendered at lower detail.
Steps to Reproduce
Expected Behavior
Grass should be visible when looking forward (within the camera view frustum) and culled
when looking down (outside the view frustum). This matches the behavior on Windows Vulkan.
Environment
Additional Notes
this bug — it's not a Vulkan renderer issue in the game engine itself.
GrassQualityin GRB.ini reduces grass density but does not fix the cullinginversion.
dependent frustum culling in the Anvil engine's Vulkan renderer path on Linux.