Update README to reflect fully functional ImGui viewer

The viewer now has all core features operational:
- Volume loading with dimension inputs
- OSG 3D slice visualization
- CPU occlusion generation
- Transfer function controls
- Real-time status monitoring

Updated usage instructions to include dimension inputs.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: MPanknin

README.md

@@ -173,15 +173,19 @@ cmake --build . --config Release
 
 **Current Status:**
 - ✅ The ImGui viewer provides a fully functional modern, cross-platform UI
-- ✅ Volume loading operational with VolumeManager integration
+- ✅ Volume loading operational with dimension inputs (Width x Height x Depth)
+- ✅ OSG 3D rendering active - displays middle slice of loaded volume
 - ✅ CPU-based occlusion generation working (CUDA integration for Linux in progress)
 - ✅ Transfer function controls with presets functional
 - ✅ Real-time status panel showing volume info and operation state
-- 🔄 Full OSG 3D volume rendering viewport integration in progress
+- 🔄 Render-to-texture integration (OSG renders to separate window currently)
 
 **Usage:**
-1. **Load a volume:** Enter path in Volume Loading panel and click "Load RAW Volume"
+1. **Load a volume:** Enter path and dimensions in Volume Loading panel
+   - Example: `data/samples/cornell_128x128x128.raw` with Width=128, Height=128, Depth=128
+   - Click "Load RAW Volume"
    - Status panel will show volume dimensions and voxel count
+   - OSG will create a 3D visualization window showing the middle slice
 2. **Generate occlusion:** Set radius (1-20) and click "Generate Occlusion Map"
    - CPU computation works on all platforms (macOS, Linux, Windows)
    - Status panel will confirm when generation is complete