PT-5 + PT-4: specular NEE, fight-perf protocol, ReSTIR DI (experimental)

[proggeramlug]

Summary

Closes out the path-tracing roadmap (docs/pt/pt-roadmap.md).

• Specular NEE at every path vertex: direct_light evaluates the GGX highlight (same D/F/V as sample_brdf) for the sun and the sampled point light - the shadow ray is already paid, so it rides free. Closes the documented PT-2 gap; the primary-only sun specular block is deleted.
• Progressive + combat = skip, not burn: tlas_version bumps every combat frame; the accumulation reset now also skips the dispatch (it used to trace at full res while showing raster). Measured PROG-in-fight cost: raster + 0.2 ms.
• PT-4 ReSTIR DI, experimental (BLOOM_PT_RESTIR=1): RIS over 8 candidates + temporal reservoir reuse through the shared SVGF reprojection basis (M-cap 20x, target re-evaluated at the current shading point, one shadow ray for the winner; bounce vertices keep plain NEE, progressive stays the pure-NEE oracle). Validated at parity vs plain NEE - delta inside the scene noise floor, no energy shift, no cost delta - exactly what the roadmap predicted for a 5-light arena. The payoff arrives with emissive-particle lights. Reservoirs raise the kernel to 9 storage buffers; max_storage_buffers_per_shader_stage is now requested from the adapter on both platforms.
• Fight-scene perf protocol (perf-round-3 rule) run and recorded, 760M / 4K / rs 0.75: raster ~45 fps light combat, 32-36 heavy; RT 27.5 / 20-23; PROG rides raster. Full matrix + hardware-verified fallback table in docs/pt/PT-5-integration-and-restir.md.

Shooter-side settings row: Bloom-Engine/shooter PR.

https://claude.ai/code/session_018574BdCfSjdpNK3WLgx1hP

Summary by CodeRabbit

• New Features
  • Added experimental ReSTIR direct-lighting support for realtime path tracing, improving point-light sampling and temporal reuse.
  • Enhanced path-traced lighting with GGX specular highlights from sunlight and point lights.
• Performance
  • Reduced unnecessary rendering work when path-tracing accumulation resets during scene or combat changes.
• Compatibility
  • Improved support across graphics adapters by accommodating path-tracing storage requirements and providing fallback behavior where advanced features are unavailable.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: deb657db-bba5-4b30-a40e-c09814c01458

📥 Commits

Reviewing files that changed from the base of the PR and between 1f6f090 and 5d2b9b5.

📒 Files selected for processing (6)

• docs/pt/PT-5-integration-and-restir.md
• native/shared/src/attach.rs
• native/shared/src/renderer/mod.rs
• native/shared/src/renderer/pt_pass.rs
• native/shared/src/renderer/shaders/pt.rs
• native/windows/src/lib.rs

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📝 Walkthrough

Walkthrough

Adds experimental PT-4 ReSTIR DI with reservoir buffers, reprojection, temporal reuse, and single-winner shadow testing. Unifies GGX specular NEE, skips progressive dispatch after TLAS resets, raises storage-buffer limits, and documents PT-5 integration and validation.

Changes

Path tracing integration

Layer / File(s)	Summary
GPU resource and capability contracts native/shared/src/attach.rs, native/windows/src/lib.rs, native/shared/src/renderer/mod.rs, native/shared/src/renderer/pt_pass.rs	Adds PT-4 reservoir fields, storage bindings, buffer allocation and resize invalidation, the BLOOM_PT_RESTIR flag, uniform wiring, and adapter storage-buffer limit configuration.
Direct lighting and ReSTIR shader pipeline native/shared/src/renderer/shaders/pt.rs	Adds GGX specular NEE for sun and point lights, reprojection state, RIS candidate selection, temporal reservoir reuse, and selected-light shadow testing.
Progressive dispatch and accumulation integration native/shared/src/renderer/pt_pass.rs, native/shared/src/renderer/shaders/pt.rs	Skips progressive dispatch after TLAS rebuilds, routes realtime PT-4 point lighting, and reuses reprojection state for SVGF accumulation and fallback history.
PT-5 integration record docs/pt/PT-5-integration-and-restir.md	Documents lighting integration, combat performance behavior, measurement results, settings and fallback gates, ReSTIR validation, and completed roadmap tickets.

Estimated code review effort: 4 (Complex) | ~60 minutes

Sequence Diagram(s)

sequenceDiagram
participant Renderer
participant PTKernel
participant ReSTIRReservoir
participant ShadowRay
Renderer->>PTKernel: dispatch realtime path-tracing pass
PTKernel->>PTKernel: compute reprojection state
PTKernel->>ReSTIRReservoir: read previous reservoir
PTKernel->>ReSTIRReservoir: write selected reservoir
PTKernel->>ShadowRay: test selected point light
ShadowRay-->>PTKernel: return visibility
PTKernel-->>Renderer: accumulate weighted lighting

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Possibly related PRs

• Bloom-Engine/engine#92: Modifies the same path-tracing renderer plumbing and PT megakernel areas.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/pt5-integration

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