[WIP] Implement advanced rendering features: skin SSS, eye shader, and hair shader with SDK/demo controls

[Copilot]

Implements PR #4 advanced rendering MVP for skin, eye, and hair shading in pure WebGL 2.0, and wires user-facing controls through the SDK and demo.

What’s implemented

Skin SSS

• Added src/renderer/SSSPass.js with a Jorge Jimenez-style separable screen-space blur (horizontal + vertical).
• Includes edge-stopping using G-buffer normals and a skin mask derived from albedo.
• Integrated into DeferredRenderer between lighting and tonemapping.
• Exposed runtime controls:
  • enable/disable
  • strength
  • width
  • RGB SSS color

Eye shading

• Added src/renderer/EyeRenderer.js with a physically-inspired eye model:
  • cornea Fresnel/specular
  • iris depth/parallax effect
  • sclera wrap-lighting contribution
• Wired demo controls for eye toggle and iris size.

Hair shading

• Added src/renderer/HairRenderer.js with Kajiya-Kay anisotropic highlights and a secondary shifted lobe.
• Added procedural card-based hair geometry helper (buildHairCards) for demo use.
• Wired demo controls for hair toggle and anisotropy/specular shaping.

SDK / API updates

• Updated src/sdk/OpenHuman.js with renderer API entry points for SSS controls:
  • setSSSEnabled
  • setSSSStrength
  • setSSSWidth
  • setSSSColor
• Added eye/hair parameter entry points for future embedding:
  • setEyeParams
  • setHairParams
• Re-exported advanced renderer modules for SDK consumers.

Demo updates

• Updated demo/index.html with advanced shading controls (toggles/sliders) and visible scene elements for skin/eye/hair improvements.
• Updated path label/HUD to reflect active advanced shading features.

Validation

• ✅ Build passes: npm run build
• ✅ Security scan: codeql_checker reported 0 alerts
• ✅ Manual visual verification completed in browser

Screenshot

• https://github.com/user-attachments/assets/6ec629af-7251-46ec-b75b-256af67b0f10

Original prompt

Create PR #4 for openhuman-ai/realistic-render-engine implementing advanced rendering features: skin screen-space subsurface scattering (SSS), eye shader with cornea/iris effects, and hair shader (Kajiya-Kay and/or card-based anisotropy).

Scope:

1. SSS: Implement Jorge Jimenez-style separable, curvature/depth-masked SSS blur for skin materials. Wire controls for SSS strength, width, and color (RGB).
2. Eye: Physically-based eye shader (cornea refraction, iris depth/parallax, sclera SSS contribution) integrated with deferred and/or forward path.
3. Hair: Card-based and/or multi-layer strand (Kajiya-Kay or Marschner-inspired, but within MVP constraints) with anisotropic highlight and shadow.
4. Update SDK API for SSS/eye/hair params per OpenHuman demo spec.
5. Update demo to show visibly improved skin softness, eye effects, and hair specularity/anisotropy, with toggles/slider controls.

Constraints:

• Pure WebGL 2.0 (GLSL 300 es, no runtime dependencies)
• Performance-aware SSS pass (scissoring, skin mask, mobile fallback)
• All code modular/per-file under src/ as per repo plan
• All features have API entry points for later SDK embedding

Detailed implementation guidance

• Implement/extend src/shaders/skin.frag.glsl, sss.frag.glsl, eye.frag.glsl, hair.frag.glsl; update/ensure JS<->GLSL uniform coupling.
• Integrate SSS as post-process after lighting, supporting strength/mask.
• For eye/hair, update geometry path and scene/Character plumbing as needed.
• Demo scene includes at least one eye, hair, and visible skin surface tested across toggles.

Acceptance:

• Skin SSS, eye, and hair shading is visibly functional in demo.
• SDK+demo API exposes relevant controls for SSS/eye/hair tuning.
• No runtime dependency is introduced.
• Code matches file structure and style established in earlier PRs.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: @copilot Accepted Confirmation: Confirm agent session

Assistant: Started — PR #2 is now in progress.

You can track it here:

data:
    - title: '[WIP] Add GPU dual-quaternion skinning and animation system'
      repository: openhuman-ai/realistic-render-engine
      url: https://github.com/copilot/tasks/pull/PR_kwDORtjZVs7MepKM?session_id=d4c94486-eb95-41da-8621-07ae3854237f
      state: queued

User: Continue with third Pull request:

PR #3: deferred + G-buffer + PBR/IBL + shadows + ACES

Assistant: Great — I’m ready to start PR #3: deferred + G-buffer + PBR/IBL + shadows + ACES on openhuman-ai/realistic-render-engine targeting main.

Please confirm and accept the GitHub confirmation prompt for the new agent session, and I’ll open PR #3 immediately with that scope.

User: Yes, I confirm.

Assistant: Perfect — proceeding with PR #3 on main.

Please accept the GitHub confirmation prompt (@Copilot Accepted Confirmation: Confirm agent session) for this new PR run, and I’ll start implementation right away.

User: @copilot Accepted Confirmation: Confirm agent session

Assistant: I’m waiting for your confirmation response in the GitHub dialog to continue with PR #3.

User: @copilot Accepted Confirmation: Confirm agent session

Assistant: Started — PR #3 is now in progress.

You can track it here:

data:
    - title: '[WIP] Implement deferred rendering pipeline with G-buffer and PBR lighting'
      repository: openhuman-ai/realistic-render-engine
      url: https://github.com/copilot/tasks/pull/PR_kwDORtjZVs7Mez_d?session_id=b777be20-170b-456d-b503-7e8c23fe7631
      state: queued

User: Let continue to fix PR #3.

Assistant: Done — I’ve sent the continuation/fix request for PR #3 and resumed work on the deferred pipeline issues (G-buffer, PBR/IBL, shadows, ACES, and demo stability) on openhuman-ai/realistic-render-engine (main).

User: @copilot Accepted Confirmation: Confirm agent session

Assistant: Great — I’ve continued the PR #3 fix pass and queued focused fixes.

Track progress here:

data:
    - title: '[WIP] Fix deferred rendering pipeline issues in PR #3'
      repository: openhuman-ai/realistic-render-engine
      url: https://github.com/copilot/tasks/pull/PR_kwDORtjZVs7Me_WY?session_id=d822f307-fb70-4128-bc0e-f6bd191efd12
      state: queued

User: #PR3 still not work, Let continue to fix by following list guide, [x] is already complete, [ ] is not complete yet. Let complete all unfinish task following:

• Explore existing codebase (ForwardRenderer, RenderTarget, Shader, StateCache, SDK, demo)
• Update src/core/RenderTarget.js — add depth-texture support (for shadow maps)
• Implement src/renderer/ShadowMap.js — depth FBO, orthographic light matrix, shadow pass, PCF
• Implement src/renderer/PostProcessStack.js — fullscreen quad, ACES tonemapping shader, pass chain
• Implement src/renderer/DeferredRenderer.js — G-buffer MRT, geometry pass (static+skinned), PBR lighting pass, IBL (BRDF LUT + ...

This pull request was created from Copilot chat.

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[hmthanh]

@copilot let continue

[Copilot]

@copilot let continue

Continued and pushed in 27a2b3f.

Implemented and wired: deferred SSS integration (including SDK controls), advanced shading demo controls/toggles, and demo scene updates for SSS/eye/hair visibility.

Screenshot: https://github.com/user-attachments/assets/6ec629af-7251-46ec-b75b-256af67b0f10