Fix round from Opus review of 87677f9c (APPROVE WITH FIXES):
1. (A1/A3) Hardened the atmospheric_filmic.frag / atmospheric_bloom_
downsample.frag shader-source pinning test: asserts the exact decode
call count (6 - three in lowFusedScene, three in main's non-fused
branch), that the 2.2 display-gamma exponent and 1/2.2 inverse in
atmospheric_common.glsl are formatted FROM AtmosphericColorPipeline
.DisplayGamma (so shader literal and CPU-tested value cannot drift),
that the 0.18 contrast pivot in atmospheric_filmic.frag is formatted
from AtmosphericColorPipeline.LinearMidGrey, and pins
AtmosphericPostProcessGraph.BloomKneeLinear/BloomThresholdLinear as
exact literals (0.73f / 1f). Also removed a stray trailing "()" from
an existing comment in atmospheric_filmic.frag that was inflating the
decode-call count to 7.
2. (B1) Re-derived the "vignette-strength" default for the linear-light
post stack. The vignette multiply now happens on linear colour before
the final encode, so a corner factor of (1 - strength) displays as
(1 - strength)^(1/2.2), not (1 - strength) directly. The accepted
look was strength 0.12 under the OLD gamma-space pipeline: a 12%
on-screen corner darkening. Under strength 0.12 in the new linear
pipeline that same 0.88 corner multiplier would only display as
0.88^(1/2.2) ~= 0.9435 (5.6% darkening - visibly weaker). Solving
(1 - strength)^(1/2.2) = 0.88 gives strength = 1 - 0.88^2.2 ~= 0.245,
which reproduces the accepted 12% corner darkening. Since
RenderPackSettingValueCodec requires every declared default to be
step-aligned from the minimum and 0.245 is not a multiple of the old
0.01 step, the step also moves to 0.005 (a finer slider, not
coarser) so the exact derived default is a valid grid point -
verified by running the ExternalTierTwoPackCanRenameEveryOwnedId
AndShaderAsset validation test, which failed with "invalid default
value" before this correction. Also updated the matching fallback in
AtmosphericPostProcessGraph.FromDescriptor (0.12f -> 0.245f) for
consistency, and added
AtmosphericColorPipelineTests.VignetteDefaultReproducesTheAccepted
TwelvePercentCornerDarkening pinning encode(1-0.245) ~= 0.88.
3. (A4) Renamed VolumetricShaftFrameParameters.LinearSunColor ->
AuthoredSunColor in VolumetricShaftQuality.cs (internal, 2 references,
both in that file - safe). Left LightSource.ColorLinear unrenamed:
grep shows 13 files depend on it (GlobalLightPacker, SceneLightingUbo,
LightBake, LightManager, EnvCellRenderer, RenderingDiagnostics, and
several Core tests) across the shared retail default-path lighting
UBO pipeline - renaming it is out of VM3's pack-only scope and would
touch the mandatory-unchanged default path. Added a pointer comment
on the field in LightSource.cs (and a one-line note at its
WorldRenderFrameBuilder.cs call site) documenting the same
display-space-not-linear fact and explaining why the rename is
deferred to its own default-path colour-space pass.
4. (B4) Added a citation beside acesFitted in both atmospheric_filmic
.frag and its C# mirror (AtmosphericColorPipeline.AcesFitted):
Krzysztof Narkowicz, "ACES Filmic Tone Mapping Curve" (2016). The fit
takes linear scene light in and returns linear display light in
[0,1] - it does not itself gamma-encode. Evidence: acesFitted(0.80 *
decode(0.46)) = 0.2064 un-encoded versus the accepted 0.51 on screen.
5. (B2) Rewrote the VM3 section of docs/plans/2026-08-22-visualmaster-
campaign.md with the shipped truth in place of the pre-implementation
guess: exposure stays 0.80 (at exposure 1.0 the linear pipeline maps
gamma-0.5 to 0.6017, essentially the same 0.6163 the owner called too
bright), bloom threshold stays 1.0 (a fixed point of both exponents),
knee moves 0.45 -> 0.73, vignette-strength moves 0.12 -> 0.245. Added
the old-vs-new curve table at exposure 0.80 across ten gamma inputs.
Replaced the acceptance criteria's "new automated test on the
recording RHI" with the CPU mirror + shader-source pins actually
used, and recorded that the real-frame masked capture WAS run
(retail vs High-with-every-effect-neutral, artifacts/vm3):
independently re-verified by re-running the pixel diff against the
checked-in screenshots - 110,561 px at |delta|=1 and exactly 95
pixels at |delta|>=5, confined to foliage-canopy silhouette edges
against sky with nothing on any ground/building/water surface. Noted
the Stage-1 luminance table re-capture is still owed at the owner
gate.
6. (B3) Corrected docs/plans/2026-08-21-atmospheric-rendering.md's VM3
summary sentence: the bloom intermediate is already linear after
extraction (no separate "bloom read" decode), and the neutral-preset
claim is now phrased as a measured numerical identity (<=1 LSB on a
real frame) rather than an unqualified "is" statement.
7. (A5) Corrected toolchain attribution: tools/compile-shaders.ps1 used
the managed Silk.NET.Shaderc path (shaderc_shared.dll) to compile in
both this round and the original VM3 commit - a Vulkan SDK glslc was
detected and its path recorded, but the managed compiler is what
actually ran. Regenerating this round only changed the atmospheric_
filmic frag stage's manifest hash (comment-only edits); the compiled
.spv bytes are unchanged, and every retail-oracle shader
(mesh_modern, terrain_modern, mesh_detail, etc.) remains untouched.
8. Replaced an invented motive in the atmospheric_filmic.frag contrast-
pivot comment ("rounded up for a stronger gamma-space contrast
feel") with the actual reason: the previous 0.5 was simply the [0,1]
midpoint of the standard contrast formula, not a deliberately chosen
value; in linear the perceptual mid-grey is 0.18.
Verify: Release build 0 warnings / 0 errors. App hermetic-filter tests:
5970 passed / 0 failed / 0 skipped. VulkanShaderManifestTests: 7/7 pass
(retail-oracle SPIR-V byte-identical; only the atmospheric_filmic frag
manifest hash changed, no .spv bytes changed).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Closes review finding F4 (docs/research/2026-08-22-campaign-ar-review.md):
retail's main-world colour, sun rays and volumetric shafts are all
gamma-encoded display-space values (the 2013 client has no linear
lighting pipeline), but bloom thresholding, ACES (Narkowicz fit),
Rec.709 luma saturation, the contrast pivot and the vignette were all
operating directly on those gamma values, then writing the result to
the UNORM swapchain without re-encoding.
- atmospheric_common.glsl gains acdreamDecodeDisplay/acdreamEncodeDisplay
(pow(c, 2.2) / pow(c, 1/2.2)). 2.2 is the retail-era CRT/early-LCD
display-gamma assumption, deliberately not the sRGB piecewise curve,
which would claim a precision retail's authoring pipeline never had.
uAtmosphereSunColor's comment is corrected from "authored linear rgb"
to "authored display-space rgb (retail has no linear pipeline)".
- atmospheric_bloom_downsample.frag, atmospheric_filmic.frag (both the
fused-Low and non-fused paths) decode every world/ray/volumetric read
before summing/thresholding; atmospheric_bloom_blur.frag is unchanged
(it already reads the now-linear bloom buffer); atmospheric_sun_rays.frag
and atmospheric_volumetric.frag are documented as writing display-space
colour that the consumers decode.
- The contrast pivot moves from 0.5 (a gamma-space midpoint) to 0.18
(linear mid-grey, the standard 18%-grey-card exposure convention).
The final filmic output is clamped in linear, then re-encoded before
the UNORM write.
- Bloom threshold/knee are re-derived for linear light: the pre-VM3
gamma-space pair was threshold 1.0 / knee 0.45, i.e. a soft range of
[0.55, 1.0] in gamma. Decoding both ends with the same 2.2 assumption
gives decode(1.0) = 1.0 (threshold unchanged) and
decode(0.55) = 0.55^2.2 ~= 0.27, so linear knee = 1.0 - 0.27 ~= 0.73.
Replaced the inline 0.45f literals with named constants
BloomThresholdLinear = 1f / BloomKneeLinear = 0.73f on
AtmosphericPostProcessGraph. bloom-strength's 0.65 default is
untouched.
- Exposure stays at its accepted 0.80 default: in linear,
encode(acesFitted(0.80 * decode(0.46))) ~= 0.50, reproducing the same
accepted midtone the old gamma-space pipeline produced as 0.51 for the
same 0.46 input (0.46 * 0.80 fed straight into acesFitted, no
decode/encode). Highlights now retain more (gamma 0.9 input moves from
~0.74 to ~0.85 through the full pipeline) and blacks deepen slightly
(gamma 0.1 moves from ~0.09 to ~0.05) — the owner's visual gate judges.
- Added AtmosphericColorPipeline, a CPU mirror of the GLSL decode/encode/
ACES/grade/filmic math (line-for-line, with a header comment requiring
it stay mirrored), and AtmosphericColorPipelineTests: neutral-preset
identity within half an 8-bit step for a 0..255 grey sweep (proving the
neutral preset is numerically the pack-off image), decode/encode
round-trip within 1e-6, monotonic-in-exposure, the pinned midtone/
highlight/shadow numbers above, and the bloom-knee derivation.
- Added a shader-source pinning test so a future edit cannot silently
drop the colour-space conversions: atmospheric_filmic.frag must
contain exactly one acdreamEncodeDisplay( call in main()'s output,
atmospheric_bloom_downsample.frag must contain at least three
acdreamDecodeDisplay( calls.
- Regenerated SPIR-V (tools/compile-shaders.ps1, glslc from the
installed Vulkan SDK). Only atmospheric_bloom_downsample.frag.spv and
atmospheric_filmic.frag.spv changed in bytes; every other pack shader
that includes atmospheric_common.glsl recompiled to a byte-identical
binary (the new decode/encode helpers are unreferenced dead code for
them). VulkanShaderManifestTests' retail-oracle SHA-256 set
(mesh_modern, terrain_modern, mesh_detail, etc.) is untouched and
still passes — the retail default path did not change.
- Docs: noted the linear-light move in the AR plan's Slice 1 section,
and added a "Colour space" section to the render-pack ABI doc
(docs/render-packs/semantic-bindings-v1.md) naming which inputs are
display-space and pointing at atmospheric_common.glsl as the
reference implementation. No ABI version bump — the binding layout
is unchanged.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Erik