refactor: move BRDFs to separate file

[jiayev]

move BRDFs to a separate hlsli file to simplify PBR.hlsli and allow them to be used by other features.

Summary by CodeRabbit

• New Features

  • Introduced a comprehensive BRDF module, providing a variety of advanced diffuse and specular reflectance models for physically based rendering.

• Refactor

  • Updated shader code to use the new BRDF module for all BRDF-related calculations, improving modularity and maintainability.

[coderabbitai]

Walkthrough

A new HLSL header file, BRDF.hlsli, is introduced to encapsulate various BRDF-related functions and models for physically based rendering. The PBR shader code is refactored to remove local BRDF implementations, instead delegating all BRDF calculations to the new BRDF.hlsli module via function calls, streamlining code organization.

Changes

File(s)	Change Summary
package/Shaders/Common/BRDF.hlsli	New file defining the BRDF namespace with multiple BRDF, Fresnel, NDF, and visibility functions.
package/Shaders/Common/PBR.hlsli	Refactored: Removed local BRDF function implementations; now includes and calls BRDF.hlsli equivalents.

Sequence Diagram(s)

sequenceDiagram
    participant Shader as PBR.hlsli
    participant BRDF as BRDF.hlsli

    Shader->>BRDF: Include BRDF.hlsli
    Shader->>BRDF: Call BRDF::Diffuse_Lambert(...)
    Shader->>BRDF: Call BRDF::F_Schlick(...)
    Shader->>BRDF: Call BRDF::D_GGX(...)
    Shader->>BRDF: Call BRDF::Vis_SmithJointApprox(...)
    Shader->>BRDF: Call BRDF::EnvBRDFApproxLazarov(...)
    BRDF-->>Shader: Return computed BRDF values

Loading

Poem

In the shaders' glade, where photons play,
A clever rabbit hops today—
Gathering BRDFs in one safe den,
Tidying code with a whisker and pen.
Now PBR shines, both neat and bright,
Thanks to modular magic and code done right!
🐇✨

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📥 Commits

Reviewing files that changed from the base of the PR and between cddb51f and de5392c.

📒 Files selected for processing (1)

• package/Shaders/Common/BRDF.hlsli (1 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• package/Shaders/Common/BRDF.hlsli

⏰ Context from checks skipped due to timeout of 90000ms (3)

• GitHub Check: Build plugin and addons
• GitHub Check: Validate shader compilation (Flatrim, .github/configs/shader-validation.yaml)
• GitHub Check: Validate shader compilation (VR, .github/configs/shader-validation-vr.yaml)

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[Copilot]

Pull Request Overview

This PR refactors the BRDF-related functions by moving them from PBR.hlsli into a new, centralized BRDF.hlsli file to simplify the PBR header and enable cross-feature reuse.

• Removed inline BRDF functions from PBR.hlsli and replaced them with calls to the BRDF namespace functions.
• Introduced a new BRDF.hlsli file containing all the refactored BRDF functions with associated documentation and source citations.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
package/Shaders/Common/PBR.hlsli	Switched from inline BRDF implementations to BRDF namespace calls and added an include for BRDF.hlsli.
package/Shaders/Common/BRDF.hlsli	New file containing all the BRDF functions with detailed documentation and source references.

[github-actions]

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