examples/Sponza no longer built natively (#164). Its closest-hit declared a
descriptor_heap sampler2D, which glslang has rejected since c8253623
("Reject descriptor_heap combined image samplers"), and main.cpp wrote it
through VkResourceDescriptorDataEXT::pCombinedImageSampler, which that union
no longer has: the descriptor heap has no combined image samplers. Both went
unnoticed because nothing builds the examples.
Sponza
- closesthit.glsl declares texture2D and sampler heap arrays and joins them
where it samples, as ui-shared.glsl and HeapDynamicIndexHit do. The
sampler slot is a second spec constant beside the image slot, so the
shader assumes nothing about where the host put it, and a constant index
keeps the example running on NVIDIA 610.43.02 (see its README). The
comment no longer says the image slot is offset by bufferStartElement;
only buffer slots are.
- main.cpp gives the heap a sampler slot, writes the albedo as a
SAMPLED_IMAGE from a view create-info, and writes the sampler into the
sampler heap from a VkSamplerCreateInfo with vkWriteSamplerDescriptorsEXT,
as UIRenderer::RegisterSampler does. SamplerVulkan's VkSampler had no use
left. The sampler keeps its linear filtering and repeat addressing and
drops anisotropy, which a hit shader cannot use: it samples at LOD 0,
without derivatives.
Docs
- README.md and examples/Sponza/README.md quote the new declarations, and
the Sponza README says why the texture and the sampler are two
descriptors. Its texture2DArray materials pattern declared a
descriptor_heap sampler2DArray, which glslang rejects as well; it now
joins a texture2DArray and a sampler.
- examples/SponzaBench/README.md drops its caveat that Sponza does not
compile.
Tests
- ExampleShaders compiles every GLSL shader under examples/ with glslang as
crafter-build does for the example (Vulkan rules, SPIR-V 1.4, shaders/ on
the include path, and the descriptor-set build where the example
registers one), so a glslang that starts rejecting one fails a test
rather than an example build nobody runs. It fails on Sponza's old
closest-hit and needs glslang only.
Closes#164.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The heap acceleration-structure read still needs the rewrite on
615.78.08; the READMEs say so and point at HeapASRead --no-workaround
for checking a newer driver. Dynamic descriptor indexing in hit shaders
is fixed there, which the README and the Sponza and SponzaBench notes
now say, and the VulkanTriangle investigation no longer contradicts
itself about llvmpipe, which advertises VK_EXT_descriptor_heap now.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Indexing a `layout(descriptor_heap)` array with a runtime (non-constant)
index inside a ray-tracing hit shader device-losts on NVIDIA 610.43.02,
for both SSBO and sampled-image descriptors. A constant/spec-constant
index is fine, and the same dynamic pattern works in fragment shaders, so
it's an RT-stage-specific driver fault — the same family as #7/#15
(descriptor-heap AS reads) and #21/#22 (RT recursion + compute TLAS push).
Unlike the AS-read fault, this cannot be worked around transparently: a
sampled image has no device-address escape hatch the way an acceleration
structure does (OpConvertUToAccelerationStructureKHR), and a buffer-only
buffer_reference rewrite would need a whole address-table architecture
while still leaving the texture half broken. So the resolution is the
documented-limitation path (the precedent set by #7).
Records the fault and its isolation in README's Native RT status and in
the Sponza example README (the textured-closest-hit example, which already
reads its albedo through a spec-constant slot for exactly this reason).
Documents the recommended consumer pattern: bind one resource and index
*within* it dynamically (single geometry SSBO / buffer_reference at a
spec-constant slot; one texture2DArray indexed by layer) rather than
selecting a descriptor dynamically — what the WebGPU path already does.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
