V6f ran the bring-up host once under VK_LAYER_KHRONOS_validation and found
seven VUIDs, every one of them on the path any world frame takes (plan
§5.5.7). This closes all of them, plus a fourth defect in the same log that
§5.5.7 did not call out. The host now runs validation-clean: zero errors and
zero warnings over 39,855 frames.
Nothing outside Gpu/Vk/ is touched, so the GL backend executes not one changed
statement. The offline pixel gate says so too — 4.08e-05 differing fraction
against f8dbe2ee, which is exactly the value the campaign recorded as its own
same-commit control (§5.1's 15–23 pixel band).
The dynamic-descriptor limit was a decision, not a patch. V6b declared all ten
of set 0's bindings STORAGE_BUFFER_DYNAMIC on the reasoning that the contract
lets a renderer bind any range per draw. That is true and still cost nothing to
honour for four of them: a dynamic descriptor buys exactly one thing, the
ability to address the SAME buffer at a DIFFERENT offset without a descriptor
write, which is the shape of a ring allocation and of nothing else. So the
ring-fed bindings — instances, batches, clip slots, instance light sets — stay
dynamic, and the ones pointing at a long-lived buffer written whole and bound
once per pass carry their offset in the descriptor instead. Binding 9 is the
clearest of those: it is the GL-only uvec2 handle table, which the Vulkan
backend never binds at all.
That lands on four dynamic storage descriptors. The RX 9070 XT allows eight, so
eight would have worked here — but four is Vulkan's GUARANTEED minimum, which
means no conformant device can fail this layout, and V9's lavapipe row and the
deferred physical Linux row both depend on that. The count is asserted against
maxDescriptorSetStorageBuffersDynamic in the capability record, so a device that
cannot serve it is rejected at startup in the report under the same exit-code-4
contract as every other requirement, rather than failing silently at
vkCreatePipelineLayout the way this one did.
Depth-off pipelines were malformed in any pass that has depth. Dynamic rendering
bakes the depth/stencil attachment format into the pipeline and requires it to
equal the pass's; V6c set it only when the pipeline itself tested or wrote
depth. Debug lines, the retained UI and the sky are all depth-off and all
composite over the main pass, so this was not an edge case. The same
GpuPipelineDescription is legitimately used both ways — ui-text opens its own
depth-less pass — so the description cannot answer the question and the backend
builds both variants, binding whichever matches what vkCmdBeginRendering was
actually handed rather than what the pass asked for. Both are built at startup
against the persisted cache, so no frame compiles one. A slice entitled to
change the contract should add a depth-format field the way V6d added
ColorFormat; this is the honest expression of the gap until then.
vk-backbuffer-depth and vk-backbuffer-msaa-color were created UNDEFINED and
never moved. Both now barrier on every backbuffer pass — from UNDEFINED on the
first use after Configure, from attachment-optimal with a write-after-write
dependency thereafter. The dependency matters on its own account, not just the
layout: two passes in one frame write both images and so does the next frame,
and Vulkan orders nothing between render-pass instances.
The fourth defect is the one worth reading twice. CaptureBackbuffer transitioned
the LAST PRESENTED swapchain image to TRANSFER_SRC and copied out of it. After
vkQueuePresentKHR that image belongs to the presentation engine and its contents
are not ours to read — and the pixels were usually right, which is precisely the
problem. This campaign spent three sections of its own plan (§5.5.1–§5.5.3)
discovering how much a capture instrument that is "usually right" can cost, and
shipping that shape on the new backend would have made every Vulkan PNG, and the
V7 differential built on them, formally undefined. The frame now copies its own
output into a host-readable buffer while it still owns the image, and the
capture reads that. Retention is opt-in, armed when an artifact directory
exists: one full-resolution copy per frame is worth nothing to a player and is
the entire instrument to a gate. The old one-shot command pool, device-idle wait
and per-capture readback buffer go with it.
Two gaps found and recorded in §5.5.8 rather than fixed, both outside this
slice's brief. UniformSkyParams (set 1, binding 4) is not in the uniform set
layout, so whoever first draws sky on Vulkan must add it. And a binding pointed
at two different buffers within one frame silently corrupts the earlier draws,
on dynamic and plain descriptors alike, because descriptor contents are read at
execution time — no consumer does that today, but WbDrawDispatcher and
EnvCellRenderer each own their own instance and batch buffers and both bind
bindings 0, 1, 3, 4 and 5 in one frame, so the Vulkan world arm has to know
before it is written.
Gates: Release build; App tests 4,075 passed / 3 skipped (baseline 4,073 + the
two new capability cases); GL offline pixel gate PASS at 4.08e-05; one
validation-layer Vulkan run, clean, with the captured PNG inspected and correct
in orientation, colour and glyph coverage.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The last of V6's three commits, and the one that makes the backend render.
Plan sections: 4.5 (pipelines and the persisted cache), 4.6 (shaders and the
committed .spv), 4.7 and 3.3 (clip space, the Y flip and winding), 4.9 and 4.10
(swapchain format and the scissor convention), 4.11 (the probe shader V5
deferred), 5.4 (Target: null means the swapchain image, literally).
WHAT RUNS. ACDREAM_RENDER_BACKEND=vulkan now renders a real scene through the
whole RHI on the RX 9070 XT: 60,000-plus frames per twelve-second run, 4x MSAA
resolving into a B8G8R8A8_UNORM swapchain, GPU timer scopes resolving, a
screenshot taken through IGpuDevice.CaptureBackbuffer, and a clean
CloseMainWindow exit with the allocator reporting three device-memory objects.
WHAT IT DRAWS, AND WHY IT IS NOT THE GAME. V6's milestone is "a full game frame
on Vulkan" and on this branch that cannot be the game's own frame. V4c and V4d
are parked by 5.5.5 so the world renderers are still raw GL; and the two
renderers that DO speak the RHI - TextRenderer and DebugLineRenderer, ported at
V4a - both throw for any device that is not a GlGpuDevice, because their loose
uniforms and their classic texture-unit sprite binding have no home in the
pinned contract yet. Converting them is a V4-class change with its own GL pixel
gate, outside this slice's file list.
So the backend is exercised through the contract by a scene of our own, and it
is not a toy. It uses a device-local mesh arena filled through the staging ring,
instance and batch data written straight into mapped ring memory, an offscreen
render target whose colour is registered into the global texture table and
sampled by a later pass, a BC1 texture with a CPU-built mip chain beside an
uncompressed one with a vkCmdBlitImage chain, one multi-draw-indirect covering
five quads with gl_DrawID selecting per-draw batch data, a second pipeline with
line-list topology bound mid-pass, dynamic cull/front-face/depth-write, push
constants, timer scopes, and an MSAA colour attachment resolving into the
swapchain image.
ORIENTATION, BY INSPECTION. Slice V5's screenshot was a uniform clear and its
orientation was right "by construction" - which a uniform clear cannot show. The
scene is therefore deliberately asymmetric in both axes: a quadrant card that is
red top-left, green top-right, blue bottom-left and white bottom-right, four
differently tinted markers at four different corners, and an open L of lines
whose short stub rises at its right end. The captured PNG reads correctly in
every one of those, including a miniature of the same card in the bottom-right
whose own quadrants are also the right way up. The negative viewport height, the
front-face inversion and the capture path agree.
THE SHADER TOOLCHAIN, AND WHAT IT FOUND. tools/compile-shaders.ps1 drives
tools/ShaderCompiler, a small out-of-solution .NET tool over Silk.NET.Shaderc -
the same shaderc glslc is built on, through the already-pinned Silk 2.23.0
family. glslc is preferred when a Vulkan SDK is present and reported when it is;
neither this machine nor CI has one, and requiring a 500 MB manual install
between a contributor and a working checkout is not a reasonable price for a
build step. The GLSL sources stay the single source of truth: the Vulkan dialect
arrives as a preamble injected after the #version line - ACDREAM_UBO_SET becomes
"set = 1,", the texture table becomes a set-2 descriptor array with a required
nonuniformEXT accessor, and the shared 96-byte push block is declared with each
loose uniform name defined onto its member. The only edits to a shader BODY are
mechanical and dialect-level: dropping default-block uniform declarations, which
Vulkan GLSL has no such thing as, and assigning explicit varying locations BY
NAME across a pair, because ordinal assignment would look identical today and
silently swap varyings the first time an author reordered a line.
Run over the eight production pairs, exactly one thing happened: none of them
compiled, and every failure is a specific source-level fact belonging to a
renderer-port slice that has not landed. debug_line needs uView/uProjection
converged into one uViewProjection - two matrices are 128 bytes and the shared
block is 96. mesh_modern and particle still pass a uvec2 bindless handle as a
varying, which is V4t's GpuTextureSlot retype. sky has ten loose uniforms and
wants a UBO. ui_text needs uScreenSize/uUseTexture/uTex. particle_mesh needs
uTextureIndex to become uTextureIndexA. terrain_modern needs V4d-1's matrix
convergence. mesh is the legacy pair with no RHI consumer at all. That inventory
is committed as shaders.manifest.json, with each source's SHA-256 and the
compiler's own message, and a test re-hashes it so an edited shader that never
got recompiled fails a build rather than shipping a stale binary.
vk_probe is the pair that does compile, and it is the shader 4.11 already asked
for: V5 recorded "build one real pipeline from the committed .spv" as its single
deliberate deviation because no toolchain existed. It is Vulkan-dialect only and
no GL renderer draws with it, so it forks nothing; it retires when the ported
world renderers become the backend's own proof.
DESCRIPTORS. Sets 0 and 1 are DYNAMIC buffer descriptors bound per flight slot,
so a per-draw range change costs a dynamic offset in vkCmdBindDescriptorSets
rather than a vkUpdateDescriptorSets in the hot path - which is what keeps 4.4's
zero-writes-per-frame property true for buffers as well as for textures. Ten
dynamic storage descriptors is above Vulkan's guaranteed minimum of four, so it
is a real requirement rather than a free choice, it fails loudly at layout
creation on a device that cannot serve it, and V9's lavapipe row must confirm
it. Unused bindings point at a shared dummy range so there is ONE set layout and
one pipeline layout; that is why binding a second pipeline mid-pass costs
nothing and disturbs neither the descriptors nor the push constants.
THE ONE MAPPING FUNCTION. VulkanViewportMapping holds the whole coordinate
reconciliation: negative viewport height, the front-face inversion that pairs
with it, and - separately - the scissor flip, which the viewport sign does NOT
perform. The V3 audit flagged that as a concrete V6 acceptance item and it is
the subtle one: vkCmdSetScissor is always top-left-origin, NdcScissorRect emits
GL bottom-left rectangles, and getting it wrong clips a doorway aperture from
the wrong edge in a scene that has one. Clip space needs nothing, as 4.7
concluded: the cameras already build [0,1]-convention projections.
CONTRACT GAP, RECORDED NOT PAPERED OVER. GpuPipelineDescription cannot name its
colour-attachment format, and Vulkan bakes that into a pipeline. Offscreen
targets therefore adopt the swapchain's B8G8R8A8_UNORM rather than a literal
RGBA order - invisible above the API, because an image is sampled through its
format's component mapping and the one CPU readback swizzles explicitly. The
honest fix is a colour-format field added in a reviewed contract commit, exactly
as GpuBlendMode.InverseAlpha and GpuVertexFormat.UByte4UInt were added when V4c
and V4d met the same wall. It is documented at
VulkanTextureFormatMapping.CanonicalColorAttachmentFormat.
The pipeline cache is persisted to the cache directory and validated by its
32-byte header against this device's vendor, device and cache UUID before use.
Drivers are required to ignore incompatible blobs, but "required to" is a poor
foundation for something that runs before anything else in the process, and the
check costs 32 bytes of comparison. Two consecutive launches report "cold" then
"reused".
Gates: Release build clean; App suite 4056 passed / 3 skipped (4037 at V6b plus
19 new); offline pixel gate PASS at a differing fraction of 5.15e-05 with a
same-commit control immediately after it at 2.84e-05 - 29 and 16 pixels of
563,200, the same class of ambient variation the campaign's 15-23 band records,
and roughly 19x under the 0.001 threshold on a commit that changes no GL code
path.
Validation layers could not be run: this machine has no Vulkan SDK, no
HKLM\SOFTWARE\Khronos\Vulkan\ExplicitLayers key, no VK_LAYER_PATH and no
VkLayer_khronos_validation.json anywhere on disk. Plan 7 already requires one
validation-clean run at V7; it needs the SDK installed first and is reported
rather than assumed here.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Erik