Reading an acceleration structure through VK_EXT_descriptor_heap aborts
with VK_ERROR_DEVICE_LOST on NVIDIA 610.43.02 — a brand-new-extension
driver fault isolated in #7 (engine setup is correct and validation-clean;
images/buffers through the same heap work, and both traceRayEXT and inline
rayQuery fault identically on the AS read).
An acceleration structure can equally be reached by its device address via
OpConvertUToAccelerationStructureKHR, which reads no descriptor and so never
touches the faulting heap path. glslang has no GLSL spelling for that
conversion, so VulkanShader rewrites the compiled SPIR-V at module-load
time: every `OpLoad %accelStruct <heap-ptr>` becomes a load of the TLAS
device address from a synthesized push-constant block followed by the
convert. RTPass pushes the active frame's TLAS address into that push
constant. User GLSL and example code are unchanged; acceleration structures
still bind into the heap normally.
The workaround is gated on Device::workaroundDescriptorHeapAS (true only on
the NVIDIA proprietary driver) and confined to one fenced block in
Crafter.Graphics-ShaderVulkan.cppm plus the RTPass push and the shaderInt64
feature toggle — delete those once a fixed NVIDIA driver ships and the heap
AS read becomes the direct path again.
Verified: VulkanTriangle ray-traces correctly on native NVIDIA (RTX 4090),
validation-layer-clean, no device loss. The SPIR-V rewrite was independently
validated with spirv-val on both the VulkanTriangle and Sponza raygen
modules.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Investigated the VK_ERROR_DEVICE_LOST on the native VulkanTriangle (#7).
Verified the engine side is correct and validation-clean: the BLAS/TLAS
build finishes before render (FinishInit waits), the built instance is
well-formed (identity transform, mask=0xFF, correct BLAS ref), and
vkWriteResourceDescriptorsEXT stores the TLAS device address at the
expected heap offset (confirmed by dumping the heap bytes). Khronos
validation 1.4.350 reports zero errors.
The fault is isolated to reading the acceleration structure through
VK_EXT_descriptor_heap:
- images/buffers via the same heap render fine (trace disabled -> the
raygen imageStore path renders a full gradient);
- both traceRayEXT and inline rayQueryEXT (no SBT) fault identically on
the AS read;
- reproduces with the AS descriptor at heap byte 0 / shader index 0 (no
offset/stride ambiguity) and regardless of pAddressRange size.
NVIDIA 610.43.02 is the only descriptor_heap implementation available
(llvmpipe lacks the extension), so there is no second implementation to
cross-check. Conclusion: driver-side fault in NVIDIA's brand-new
VK_EXT_descriptor_heap acceleration-structure path; should be reported to
NVIDIA. The traceRayEXT call is left active so the example stays a
faithful reproducer. Documented in both READMEs.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
