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docs(render): measure the terrain clip block's set, and close the shader audit

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Slice V6i-1 recorded terrain_modern.vert's TerrainClip block as landing in the
wrong descriptor set under the Vulkan dialect. That was reasoning from the
missing ACDREAM_UBO_SET macro; it is now measured. Disassembling the committed
spv/terrain_modern.vert.spv shows the block as OpVariable ... Uniform decorated
DescriptorSet 0 / Binding 2, where set 0's layout declares a storage buffer.

The audit the section asked for is also done rather than deferred. Every
compiled .spv was disassembled: mesh_modern.vert's nine set-0 entries are all
StorageBuffer, correctly, and every other uniform block in every other shader
already carries the macro. terrain_modern.vert is the only one. sky.vert is the
precedent - it declares the SAME shared clip block as ACDREAM_UBO_SET binding =
2 - so there is no numbering question for the world arm to settle, only a
one-word omission to fix, plus declaring set 1 bindings 2 and 4 in the uniform
set layout. Binding 4 is section 5.5.8's still-open UniformSkyParams, which
sky.vert and sky.frag both declare.

Documentation only; no source, shader or .spv is touched.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Erik 2026-07-28 13:19:13 +02:00
parent df6e2a7918
commit 0ca802cd7f
1 changed files with 22 additions and 10 deletions
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32
docs/plans/2026-07-27-vulkan-campaign.md
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@ -1552,16 +1552,28 @@ one this slice measured:
needs, so the missing piece is an `ITextureArray` implementation over
`IGpuTexture`, not a codec.
2. **`terrain_modern.vert`'s `TerrainClip` block is in the wrong set for Vulkan,
and it is the same class of gap §5.5.8 recorded for `UniformSkyParams`.** It
is declared `layout(std140, binding = 2) uniform TerrainClip` with **no
`ACDREAM_UBO_SET`**, so under the Vulkan dialect it lands at set 0 binding 2 —
which set 0's layout declares as a STORAGE buffer. GL is unaffected (the macro
expands to nothing and the UBO namespace is separate), and nothing has caught
it because no terrain pipeline has ever been created on Vulkan. Whoever draws
terrain must add the macro, declare binding 2 in the uniform set layout, and
raise `DynamicUniformBindingCount` to 3 — still far under the guaranteed 8.
Worth auditing every remaining shader for the same omission in the same pass.
2. **`terrain_modern.vert`'s `TerrainClip` block is in the wrong descriptor set,
measured on the committed SPIR-V.** It is declared
`layout(std140, binding = 2) uniform TerrainClip` with **no
`ACDREAM_UBO_SET`**, so under the Vulkan dialect it lands in set 0.
Disassembling `spv/terrain_modern.vert.spv` confirms it rather than infers it:
the block is `OpVariable ... Uniform` decorated `DescriptorSet 0` / `Binding
2`, and set 0's layout declares binding 2 as a STORAGE buffer. A terrain
pipeline built against the shared layout is therefore malformed. GL is
unaffected — the macro expands to nothing and GL's UBO namespace is separate —
and nothing has caught it because no terrain pipeline has ever been created on
Vulkan.
**The audit is done and this is the only one.** Every compiled `.spv` was
disassembled: `mesh_modern.vert`'s nine set-0 entries are all
`StorageBuffer`, correctly; every other uniform block in every other shader
already carries the macro. `sky.vert` is the precedent — it declares the SAME
block as `ACDREAM_UBO_SET binding = 2` — so there is no numbering question to
settle, only a one-word omission to fix. The fix is that word plus declaring
bindings 2 and 4 in `VulkanPipelineLayouts.CreateUniformSetLayout` (4 is
§5.5.8's still-open `UniformSkyParams`, which `sky.vert` and `sky.frag` both
declare) and raising `DynamicUniformBindingCount` accordingly — still far
under Vulkan's guaranteed 8.
3. **The flat-versus-PView question decides how much of the world arm is one
slice.** `WorldSceneRenderer` is already backend-neutral — it takes