tinyusdz/ENHANCEMENT_SUMMARY.txt

TINYUSDZ CRATE WRITER - ENHANCEMENT OPPORTUNITIES SUMMARY
=========================================================

ANALYSIS DATE: November 19, 2025
CURRENT TEST STATUS: 74 tests passing
REPOSITORY: crate-writer-2025 branch

=== QUICK STATUS ===

Shader Types Fully Supported (4):
  ✓ UsdPreviewSurface (with timesampled inputs)
  ✓ UsdUVTexture (with timesampled inputs)
  ✓ UsdTransform2d (with timesampled inputs)
  ✓ UsdPrimvarReader_* (all 10 variants)

Shader Types Partially/Not Supported (4):
  ⚠ NodeGraph (declared but empty - needs full implementation)
  ✗ UsdRamp, UsdColorSpace (not in codebase)
  ✗ Math nodes: UsdAdd, UsdMultiply, UsdMix, etc.

Light Types Fully Supported (6):
  ✓ SphereLight
  ✓ RectLight
  ✓ DiskLight
  ✓ CylinderLight
  ✓ DistantLight
  ✓ DomeLight

Light Types Partially Supported (3):
  ⚠ GeometryLight (has geometry rel, missing light API properties)
  ⚠ PortalLight (empty struct)
  ⚠ PluginLight (empty struct)

Geometry Types: 95% Complete
  All major types supported: Mesh, Curves, Points, Shapes, Camera, Subsets
  Recent additions: BasisCurves, NurbsCurves, PointInstancer enhancements

Composition Arcs: 60% Complete
  ✓ References, Payloads, Inherits, Over, SubLayers
  ⚠ Specializes (not yet implemented)
  ⚠ VariantSets composition (partial - variant processing exists)

Animation/TimeSamples:
  ✓ Attribute TimeSamples (with shader input support)
  ✓ Visibility TimeSamples
  ⚠ Relationship TimeSamples (not supported)
  ⚠ Indexed Primvar TimeSamples (known limitation)

Material/Shader Features:
  ✓ Surface/Displacement/Volume outputs
  ✓ Shader input connections
  ✓ Material binding (direct and collection-based)
  ⚠ Light filters (not yet supported - TODO comment at line 60, 116)
  ⚠ SDR metadata (not yet supported - TODO comment at line 25-28)
  ⚠ interfaceOnly connections (not yet supported - TODO comment at line 26)
  ⚠ Material fallback value serialization (needs verification)

=== TOP 3 HIGHEST PRIORITY ENHANCEMENTS ===

1. LIGHT FILTER SUPPORT (HIGH PRIORITY)
   Impact: HIGH - Required for professional lighting setups
   Effort: MEDIUM (2-3 days)
   Files: usdLux.hh
   Details: Add rel light:filters relationship type, light linking support
   Blocker: None - can be done immediately

2. NODEGRAPH FULL IMPLEMENTATION (HIGH PRIORITY)
   Impact: HIGH - Enables complex shader networks beyond chains
   Effort: MEDIUM-HIGH (3-4 days)
   Files: usdShade.hh, usdc-writer.cc
   Details: Add properties container, connectivity validation
   Blocker: None - can be done immediately

3. COMPOSITION ARC ENHANCEMENTS - SPECIALIZES (HIGH PRIORITY)
   Impact: MEDIUM-HIGH - Advanced scene organization
   Effort: MEDIUM (2-3 days)
   Files: composition.hh, stage.hh
   Details: Add specializes arc processing, variant composition
   Blocker: None - can be done immediately

=== SECONDARY PRIORITIES ===

4. ADDITIONAL SHADER NETWORK NODES (MEDIUM)
   - UsdAdd, UsdMultiply, UsdMix, UsdSeparateXYZ, UsdCombineXYZ, UsdRamp
   - Effort: 3-5 days
   - Impact: Expands shader network expressiveness

5. GEOMETRY LIGHT COMPLETION (MEDIUM)
   - Add Light API properties to GeometryLight struct
   - Effort: 1 day
   - Impact: Enables procedural lighting

6. SDR METADATA SUPPORT (MEDIUM)
   - Shader documentation and tool integration
   - Effort: 2 days
   - Impact: Improves developer experience

=== KNOWN LIMITATIONS ===

Low Priority Issues:
- Indexed primvar animation (rare use case, high effort)
- PortalLight and PluginLight (specialized cases)
- Active metadata (rarely used)
- Relationship TimeSamples (very rare)

=== RECOMMENDED IMPLEMENTATION ORDER ===

RELEASE N:
  - Light Filter Relationships (HIGH impact, medium effort)
  - GeometryLight Full Properties (QUICK win)

RELEASE N+1:
  - NodeGraph Implementation (HIGH impact, medium effort)
  - Specialize Composition Arc (HIGH impact)

RELEASE N+2:
  - Additional Shader Nodes (MEDIUM impact, variable effort)
  - Variant Composition Integration (completion of existing work)

=== FILE LOCATIONS SUMMARY ===

Core Schema Files:
  - /src/usdShade.hh       (lines 44-348)   - Shader definitions
  - /src/usdLux.hh          (lines 30-244)   - Light definitions
  - /src/usdGeom.hh         (lines 34-1100+) - Geometry definitions
  - /src/composition.hh     (lines 30-150)   - Composition arcs

Writer Files:
  - /src/usdc-writer.cc     - Main USDC writer
  - /src/crate-writer.cc/hh - Experimental crate writer framework

=== RECENT IMPROVEMENTS ===

Last 5 commits addressing enhancements:
1. Add comprehensive validation system (commit 3af0af81)
2. Add timesampled shader input support (commits c1a7b078, c0ca8bd7)
3. Add enhanced PointInstancer properties (commit 8f76cadd)
4. Add comprehensive enhancements (commit d445ef64)
   - Variant support
   - Light types (6 types)
   - Error context stack
   - Memory limits

=== TEST COVERAGE ===

Current: 74 tests passing
Recommended additions for enhancements:
  Test 75-76: Light filters and GeometryLight
  Test 77-78: NodeGraph implementations
  Test 79: Specialize arc composition
  Test 80-87: Additional shader nodes
  Test 88-90: Other enhancements

=== HOW TO USE THIS ANALYSIS ===

1. Read CRATE_WRITER_ANALYSIS.md for full detailed analysis
2. Refer to section 7 for high-priority opportunities
3. Check section 8 for recommended implementation sequence
4. Use file locations from section 10 to navigate codebase
5. Review test recommendations in section 9

=== CONCLUSION ===

The crate writer is approximately 80-85% complete for core USD features.
Remaining work focuses on:
  - Professional-grade features (light filters, advanced shaders)
  - Complex material hierarchies (NodeGraph)
  - Advanced composition patterns (Specialize, VariantSets)
  - Specialized geometry and lighting features

All recommended enhancements can be implemented without breaking changes.
The codebase has good architecture for adding these features incrementally.

For questions about specific features, refer to the detailed analysis document.