Fix issue 399 in AiDotNet

[ooples]

…399)

This commit implements Phase 3 of the AiDotNet roadmap, adding comprehensive 3D AI capabilities including point cloud processing and neural radiance fields.

Point Cloud Processing

Models Implemented

• PointNet: Pioneering architecture for direct point cloud processing

  • Permutation invariant design
  • Spatial transformer networks (T-Net) for alignment
  • Global and local feature extraction
  • Classification and segmentation support

• PointNet++: Hierarchical feature learning extension

  • Multi-scale set abstraction layers
  • Improved handling of non-uniform point density
  • Better performance on complex shapes
  • Hierarchical sampling with local grouping

• DGCNN: Dynamic Graph CNN with edge convolutions

  • Dynamic k-NN graph construction
  • Edge convolution for local geometry
  • Adaptive neighborhood structure
  • State-of-the-art classification performance

Components

• Point cloud interfaces and data structures
• Specialized layers (PointConvolution, MaxPooling, T-Net)
• Task implementations (classification, segmentation)
• Comprehensive documentation with examples

Neural Radiance Fields

Models Implemented

• NeRF: Original neural radiance fields

  • Continuous 5D scene representation
  • Positional encoding for high-frequency details
  • Volume rendering pipeline
  • Hierarchical sampling

• Instant-NGP: Fast NeRF with hash encoding

  • 100× faster training (minutes vs hours)
  • 1000× faster rendering (milliseconds vs seconds)
  • Multiresolution hash encoding
  • Tiny MLP architecture
  • Occupancy grids for efficient sampling

• 3D Gaussian Splatting: Real-time rendering

  • 100+ FPS rendering performance
  • Explicit 3D Gaussian representation
  • Adaptive densification
  • Photorealistic quality
  • Easy scene editing

Components

• Radiance field interfaces
• Ray data structures
• Volume rendering implementations
• Comprehensive documentation

Testing

• Unit tests for PointNet and point cloud data structures
• Unit tests for NeRF and radiance field models
• Integration with existing test framework

Documentation

• Complete 3D AI features documentation
• Usage examples for all models
• Performance comparisons
• Application scenarios
• References to original papers

Architecture Patterns

• Follows existing AiDotNet patterns
• Interface-based design
• Generic type support
• Comprehensive XML documentation
• Educational comments for beginners

This implementation addresses Issue #399 and provides critical 3D AI capabilities for autonomous driving, robotics, AR/VR, 3D reconstruction, and novel view synthesis applications.

Resolves #399

User Story / Context

• Reference: [US-XXX] (if applicable)
• Base branch: merge-dev2-to-master

Summary

• What changed and why (scoped strictly to the user story / PR intent)

Verification

• [ ] Builds succeed (scoped to changed projects)
• [ ] Unit tests pass locally
• [ ] Code coverage >= 90% for touched code
• [ ] Codecov upload succeeded (if token configured)
• [ ] TFM verification (net46, net6.0, net8.0) passes (if packaging)
• [ ] No unresolved Copilot comments on HEAD

Copilot Review Loop (Outcome-Based)

Record counts before/after your last push:

• Comments on HEAD BEFORE: [N]
• Comments on HEAD AFTER (60s): [M]
• Final HEAD SHA: [sha]

Files Modified

• [ ] List files changed (must align with scope)

Notes

• Any follow-ups, caveats, or migration details

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📥 Commits

Reviewing files that changed from the base of the PR and between f99b0d2cc5304fcd1d2d0645a1c925a171c2ad99 and cf66984de7a09d97822a65fa3312c74af695ccf3.

📒 Files selected for processing (18)

• docs/3D_AI_Features.md (1 hunks)
• src/NeuralRadianceFields/Data/Ray.cs (1 hunks)
• src/NeuralRadianceFields/Interfaces/IRadianceField.cs (1 hunks)
• src/NeuralRadianceFields/Models/GaussianSplatting.cs (1 hunks)
• src/NeuralRadianceFields/Models/InstantNGP.cs (1 hunks)
• src/NeuralRadianceFields/Models/NeRF.cs (1 hunks)
• src/PointCloud/Data/PointCloudData.cs (1 hunks)
• src/PointCloud/Interfaces/IPointCloudClassification.cs (1 hunks)
• src/PointCloud/Interfaces/IPointCloudModel.cs (1 hunks)
• src/PointCloud/Interfaces/IPointCloudSegmentation.cs (1 hunks)
• src/PointCloud/Layers/MaxPoolingLayer.cs (1 hunks)
• src/PointCloud/Layers/PointConvolutionLayer.cs (1 hunks)
• src/PointCloud/Layers/TNetLayer.cs (1 hunks)
• src/PointCloud/Models/DGCNN.cs (1 hunks)
• src/PointCloud/Models/PointNet.cs (1 hunks)
• src/PointCloud/Models/PointNetPlusPlus.cs (1 hunks)
• tests/AiDotNet.Tests/UnitTests/NeuralRadianceFields/NeRFTests.cs (1 hunks)
• tests/AiDotNet.Tests/UnitTests/PointCloud/PointNetTests.cs (1 hunks)

✨ Finishing touches

• [ ] 📝 Generate docstrings

🧪 Generate unit tests (beta)

• [ ] Create PR with unit tests
• [ ] Post copyable unit tests in a comment
• [ ] Commit unit tests in branch claude/fix-issue-399-011CUvzeNZ7hDC8g9id684qZ

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