Story 2.3: Multi-Primitive Scene Management

[nurusanwe]

Summary

Implements comprehensive multi-primitive scene management system for educational ray tracing with:

• Scene Management: Complete Scene class with efficient std::vector-based primitive and material containers
• Enhanced Sphere Class: Material indexing, comprehensive validation, and detailed mathematical documentation
• Robust Intersection Algorithm: Closest-hit logic with proper depth testing and self-intersection avoidance
• Data-Driven Configuration: SceneLoader with simple text format parsing and graceful error handling
• Educational Performance Monitoring: Detailed timing and statistics for understanding algorithm complexity

Key Features

• Multi-sphere intersection testing with O(n) complexity and educational transparency
• Material-aware primitive management with bounds checking and validation
• Scene file loading from simple text format with comprehensive error handling
• Performance statistics tracking for intersection count, hit rate, and timing analysis
• Backward compatibility maintained with existing single-sphere rendering pipeline
• Integration with Story 2.2 camera system for complete multi-primitive rendering

Test Coverage

• Mathematical correctness validation for multi-sphere intersection algorithms
• Edge case testing including tangent rays, self-intersection avoidance, and numerical stability
• Scene loading validation with malformed input handling and material assignment verification
• Performance monitoring accuracy testing with expected intersection count validation
• Integration testing with existing camera system and rendering pipeline

QA Results

✅ Approved by Senior Developer QA (Quinn)

• All acceptance criteria fully satisfied
• Exceptional code quality with comprehensive educational value
• No security concerns or performance issues identified
• Build system integration successful with all tests passing

Files Changed

New Files:

• src/core/scene.hpp - Scene class with multi-primitive management
• src/core/scene_loader.hpp - SceneLoader for parsing scene files
• assets/simple_scene.scene - Example multi-sphere scene file
• docs/stories/2.3.multi-primitive-scene-management.md - Complete story documentation

Modified Files:

• src/core/sphere.hpp - Enhanced with material indexing and validation
• src/main.cpp - Integrated scene loading and multi-primitive testing
• tests/test_math_correctness.cpp - Added comprehensive multi-primitive validation tests

Ready for merge into main branch.