fix: use Smith GGX visibility approximation

[PenguinDOOM]

Summary

• replace the shared PBR/Hybrid direct GGX visibility path with the linearized Smith joint GGX approximation using academic roughness p^2
• keep the GGX distribution's p^4 ownership, add normal/Switch denominator handling, and retain direct-specular arithmetic in float through NdotL
• add analytical, source-contract, and GPU coverage plus schema v4 direct-light evidence that isolates ForwardBase as one-light minus zero-light and ForwardAdd as two-lights minus one-light
• document provenance, formula behavior, evidence limits, and final v4 capture metadata in English and Japanese

Validation

• focused source, analytical, GPU visibility, PBR/Hybrid roughness, and brightness controls: 11 passed
• v4 legacy and fast GPU evidence captures: 1/1 passed each; 69 matched image pairs with byte-identical inputs
• manual v4 visual review: approved; fixed-fixture comparison recorded 0 differing pixels/channels and maximum absolute channel delta 0
• pwsh -NoProfile -File "D:\VRChatProjects\Pure-Base\Packages\jp.penguin.purebase\Tests\Run-PureBaseRegression.ps1" -Mode Daily: 99 passed, 0 failed, 0 skipped
• canonical BIRP baseline, Shader-Core ProjectSettings, and tracked package tree were unchanged by the final Daily run

Limitations

• SHADER_API_SWITCH has source/formula coverage but no Switch runtime execution.
• Local Release validation is intentionally deferred to the parent Issue PBRとHybridの明るさ・品質・性能を改善する #1 workflow.

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 114 complexity · 6 duplication

Metric	Results
Complexity	114
Duplication	6

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[Copilot]

Pull request overview

Updates Pure-Base’s shared PBR/Hybrid direct-light GGX visibility term to use a linearized Smith joint GGX approximation (using academic roughness a = p^2), and adds focused source/analytical/GPU-contract evidence plus documentation updates to support the behavior change.

Changes:

• Replace the direct GGX visibility calculation in PureBasePbrEvaluateDirect with a new shared helper implementing the linearized Smith joint GGX visibility approximation (Switch-aware denominator handling included).
• Extend Daily EditMode tests with analytical/source-layout contracts and optional external evidence export to validate finiteness, degeneracies, and pass isolation behavior.
• Update technical documentation and NOTICE with provenance, formula details, and evidence metadata.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Tests/Daily/Editor/PureBaseToonLightingContractTests.PbrRoughnessRuntime.cs	Adds runtime capture support for full-frame visibility observations and evidence artifact writing.
Tests/Daily/Editor/PureBaseToonLightingContractTests.PbrRoughness.cs	Adds visibility reference-case tests plus opt-in external evidence export flow and JSON manifest building.
Tests/Daily/Editor/PureBasePbrVisibilityApproximationTests.cs.meta	Adds Unity .meta for the new test file.
Tests/Daily/Editor/PureBasePbrVisibilityApproximationTests.cs	Adds analytical characterization and source-layout contracts ensuring the intended fast visibility helper is used and shaped correctly.
Shaders/Common/pbr_brdf.hlsl	Introduces PureBasePbrEvaluateSmithJointGgxVisibility and updates direct BRDF evaluation to use it with widened float arithmetic.
NOTICE	Adds visibility-term provenance and Unity behavior-reference clarification.
Docs/technical-information.md	Documents the new direct GGX visibility helper, formula, and evidence scope/limits (English).
Docs/technical-information.ja.md	Documents the new direct GGX visibility helper, formula, and evidence scope/limits (Japanese).
Docs/pure-base-shader-contract.md	Updates shader contract documentation to reflect the new direct GGX visibility behavior and evidence summary.

Files not reviewed (1)

• Tests/Daily/Editor/PureBasePbrVisibilityApproximationTests.cs.meta: Generated file

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