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>
Replace the megakernel @compute entry with five wavefront kernels sharing
one module, connected by GPU ray/hit/payload buffers and a GPU-driven
indirect bounce loop:
GENERATE -> (PREP -> TRACE -> SHADE) x maxDepth -> RESOLVE
- TRACE contains zero user code (pure _rtwTraverseTlas/Blas, opaque-only).
- PREP publishes dispatchWorkgroupsIndirect args from the live ray count;
the indirect-args buffer lives in its own bind group so it is never
bound read-write in the same dispatch that consumes it as INDIRECT.
- New emit/accumulate API: rtEmitPrimaryRay / rtEmitRay / rtAccumulate,
plus an optional user Resolve stage (tonemap hook; identity by default).
- Per-pass WfParams via a dynamic-offset uniform ring (curIsA/bounce vary
between passes within one submit).
- Payload-typed wfPayload binding emitted in the codegen region after the
user's struct Payload; payload travels with each ray (2*W*H slots).
- Request maxBufferSize / maxStorageBufferBindingSize / maxComputeWorkgroups
PerDimension so the W*H-sized work buffers fit past the 128MB baseline.
VulkanTriangle ported to the new API and renders bit-identical to the
megakernel baseline at maxDepth=1.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
