Syoyo Fujita 69e5426ac6 Add OpenUSD Crate format analysis and C++ examples ...

Comprehensive documentation and working C++ examples for OpenUSD's
Crate (USDC binary) format implementation.

Documentation (crate-impl.md, 1249 lines):
- Complete binary format specification with diagrams
- File layout: Bootstrap, Value Data, Structural Sections, TOC
- Key data structures: ValueRep (8 bytes), Spec, Field, TimeSamples
- Type system: All 60 supported types documented
- Reading implementation: 3 ByteStream backends (mmap/pread/asset)
- Writing implementation: Packing, deduplication, async I/O
- Compression: Integer/float/LZ4 algorithms detailed
- Deduplication: 3-level system (structural/per-type/time arrays)
- Version history: 13 versions (0.0.1 to 0.13.0)
- Optimizations: Zero-copy arrays, parallel construction, etc.
- Performance: Read/write speeds, memory usage, file sizes
- Security: Bounds checking, recursion protection, validation

C++ Examples (aousd/crate/):
Three working programs demonstrating OpenUSD C++ API:

1. crate_reader (157 KB)
   - Read .usdc/.usda files
   - Traverse prim hierarchy
   - Display attributes and TimeSamples
   - Works with any USD file

2. crate_writer (329 KB)
   - Create animated USD scenes
   - Write TimeSamples for animation
   - Animated transforms and colors
   - Simple and complex scene modes

3. crate_internal_api (169 KB)
   - Inspect binary format (magic, version, TOC)
   - Analyze TimeSamples (uniform/non-uniform sampling)
   - Compare format sizes (ASCII vs binary)
   - Low-level format introspection

Build Systems:
- Makefile: Simple, fast Unix builds
- CMake: Cross-platform, IDE integration
- build.sh: Convenience wrapper script
- Both monolithic and standard USD linking
- Links against no-python OpenUSD builds

Documentation:
- README.md: Complete build/usage instructions
- EXAMPLES_OUTPUT.md: Actual program outputs
- Full API usage examples
- Troubleshooting guide

Verified Working:
- Compiles with C++17
- Links against libusd_ms.so (monolithic)
- Creates/reads .usdc files successfully
- Binary format inspection working
- TimeSamples encoding/decoding functional

File sizes: ~660 KB total (all 3 programs)
Binary compression: 50-60% smaller than ASCII

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

2025-11-01 06:37:26 +09:00

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