ARC Raiders shows a severe and repeatable lighting misrender when using Dynamic RTX Global Illumination through the DX12/DXR path on an Intel Arc A770.

The problem is especially visible on the Stella Montis map. Parts of the maps have receive excessive indirect lighting excessively blue or over-bright while adjacent regions remain unusually dark, often with a sharp spatial boundary between them. Ceiling and wall surfaces can appear heavily over-illuminated where there is a overhead light.

The game does not hang or report device loss. This is a rendering issue.

RTX-GI Dynamic (Odd blue lighting)

RTX-GI Static (Correct)

System

GPU: Intel Arc A770 [8086:56a0] (DG2, revision 08)
Kernel driver: xe
Mesa / Vulkan driver: Mesa 26.1.3-arch3.1, Vulkan: 1.4.350
Kernel: 7.1.2-3-cachyos
Distro: CachyOS / Arch Linux
Display server: Wayland
Proton tested: Proton 10.0-4, Proton Experimental-11.0-20260701b
CPU: Intel Core i9-14900
Motherboard: ROG STRIX Z690-I GAMING WIFI
Single GPU (no iGPU active), ReBAR enabled

Symptom

Launch ARC Raiders (build-4232071c346c0a7) and load into Stella Montis; lighting issues can be seen with overhead lights in Central Corridor, Cargo Dock B ramp into Atrium, and left side of Cafeteria, seed vault extract.

Workarounds tried (all unsuccessful)

• Clearing the Steam shader cache
• Clearing the Mesa shader cache
• Disabling the vkd3d-proton shader cache with:

  VKD3D_SHADER_CACHE_PATH=0

• Forcing a single vkd3d-proton queue:

VKD3D_CONFIG=single_queue

• Disabling Vulkan descriptor buffers:

VKD3D_DISABLE_EXTENSIONS=VK_EXT_descriptor_buffer

• Forcing additional Intel synchronization:

INTEL_DEBUG=stall

• Testing Intel ray-tracing shader SIMD widths:

INTEL_SIMD_DEBUG=rt8
INTEL_SIMD_DEBUG=rt16
INTEL_SIMD_DEBUG=rt32

• Testing Intel compute shader SIMD widths:

INTEL_SIMD_DEBUG=cs8
INTEL_SIMD_DEBUG=cs16
INTEL_SIMD_DEBUG=cs32

• Testing extra RTAS synchronization:

VKD3D_CONFIG=extra_rtas_sync

The only effective workaround is to avoid the Dynamic DXR path by either:

Use RTXGI Static

or:

VKD3D_CONFIG=nodxr %command% -dx12

Log files

arc-vkd3d.log