fix(upscaling): fix mipbias sometimes being wrong

[doodlum]

Summary by CodeRabbit

• Bug Fixes
  • Fixed inconsistent texture sharpness when upscaling or switching anti-aliasing, preventing lingering blur/sharpen artifacts.
  • Ensured correct render size is applied during upscaling for stable image quality across scenes and menus.
  • Resolved cases where texture mip bias could persist after upscaling was disabled, eliminating unintended softness.
  • Reduced visual popping by making LOD transitions more consistent when toggling temporal effects or upscaling options.
  • Lowered default upscaling sharpening intensity to remove excessive sharpness while preserving stability.

[coderabbitai]

Walkthrough

State::UpdateSharedData parameters annotated with [[maybe_unused]]; upscaling render-size calc no longer depends on a_inWorld/a_prepass and uses ConvertToDynamic(screenSize, true) when temporal is enabled and upscaleMethod != kTAA. MipBias is recalculated from renderSize/screenSize ratio with an explicit else setting MipBias = 0. FSR3 dispatch sharpness set to 0.0f (sharpening intensity disabled).

Changes

Cohort / File(s)	Summary of Changes
State shared-data update src/State.cpp	Annotated UpdateSharedData params with [[maybe_unused]]. Removed dependence on a_inWorld/a_prepass for upscaling trigger; use temporal && upscaleMethod != kTAA. Compute renderSize via ConvertToDynamic(screenSize, true). Recompute MipBias = log2(screenSize.x / renderSize.x) and add else branch setting MipBias = 0.
FSR3 upscaling config src/Features/Upscaling/FidelityFX.cpp	Set FSR3 dispatch sharpness parameter from 0.5f to 0.0f (disable sharpening intensity while enableSharpening flag remains).

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant Caller as Caller
  participant State as State::UpdateSharedData
  participant Config as Temporal/Scaling Config
  participant SD as SharedData

  Caller->>State: UpdateSharedData(a_inWorld, a_prepass)
  note right of State: params marked [[maybe_unused]]

  State->>Config: read temporalEnabled, upscaleMethod
  alt temporalEnabled AND upscaleMethod != kTAA
    State->>State: renderSize = ConvertToDynamic(screenSize, true)
    State->>SD: MipBias = log2(screenSize.x / renderSize.x)
  else
    State->>SD: MipBias = 0
  end

  State-->>Caller: return

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sequenceDiagram
  autonumber
  participant Upscaler as FSR3 Dispatcher
  participant Params as Dispatch Params

  Upscaler->>Params: prepare params (enableSharpening = true)
  note right of Params: sharpness explicitly set to 0.0f
  Upscaler->>Upscaler: dispatch with sharpness = 0.0

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• fix: fix for terrain variation with upscaling feature breaking mips #1364 — Uses SharedData::MipBias in terrain variation shaders; directly impacted by MipBias recalculation here.
• chore(upscaling): improve upscaling for xess and fsr #1466 — Also touches upscaling pipeline/sharpening configuration; related to the FSR3 sharpness change.
• feat(upscaling): add nis sharpening #1457 — Modifies FSR3 sharpening flags/parameters; overlaps with the sharpening intensity change.

Suggested reviewers

• jiayev
• alandtse

Poem

I nibble bits where mipmaps grow,
I scale the pixels soft and slow.
When temporal rules and TAA’s away,
I compute new sizes—hip hooray! 🥕
Sharpness set to zero, I hop and sew.

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The title concisely and accurately summarizes the primary change—fixing incorrect MipBias handling in the upscaling code. It is short, specific, and developer-focused, matching the UpdateSharedData changes that ensure MipBias is set consistently. Omitting minor ancillary tweaks (like the FSR3 sharpness adjustment) is acceptable because the title only needs to reflect the main fix.

✨ Finishing touches

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🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch mipbias-fix-2

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[github-actions]

Using provided base ref: b1b8ee8
Using base ref: b1b8ee8
Base commit date: 2025-09-24T16:25:22+01:00 (Wednesday, September 24, 2025 04:25 PM)
No actionable suggestions for changed features.

[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

src/Features/Upscaling/FidelityFX.cpp (1)

304-306: Skip RCAS when sharpness is 0 to avoid a no-op pass

enableSharpening is true while sharpness is 0.0f. If the SDK doesn’t already short-circuit RCAS at zero, this needlessly schedules work. Consider disabling the stage when sharpness is zero.

-        dispatchParameters.enableSharpening = true;
-        dispatchParameters.sharpness = 0.0f;
+        dispatchParameters.enableSharpening = false; // sharpness is 0, skip RCAS
+        dispatchParameters.sharpness = 0.0f;

If you plan to expose sharpness dynamically later, gate it instead:

const float sharpness = 0.0f; // from settings
dispatchParameters.enableSharpening = sharpness > 0.0f;
dispatchParameters.sharpness = sharpness;

Please confirm whether the current FSR3 SDK already bypasses RCAS when sharpness == 0; if it does, keeping enableSharpening = true is fine.

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• src/Features/Upscaling/FidelityFX.cpp (1 hunks)

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[github-actions]

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