# How To

Quick reference for common tasks.

---

## Building

### Workspace Selection
```bash
# Main demo (default)
cmake -S . -B build -DDEMO_WORKSPACE=main
cmake --build build -j4
./build/demo64k

# Test demo
cmake -S . -B build_test -DDEMO_WORKSPACE=test
cmake --build build_test -j4
./build_test/test_demo
```

### Debug Build
```bash
cmake -S . -B build
cmake --build build -j4
./build/demo64k
```
Options: `--fullscreen`, `--resolution WxH`, `--seek TIME`, `--hot-reload`

### Production Builds
```bash
# Size-optimized (development)
cmake -B build -DDEMO_SIZE_OPT=ON && cmake --build build -j4

# 64k target (full checks, no debug)
cmake -B build -DDEMO_STRIP_ALL=ON && cmake --build build -j4

# Final release (no checks, absolute minimum)
./scripts/build_final.sh
```

### Developer Build
```bash
cmake -B build -DDEMO_BUILD_TESTS=ON -DDEMO_BUILD_TOOLS=ON
cmake --build build -j4
```

### Headless Testing
```bash
cmake -B build_headless -DDEMO_HEADLESS=ON && cmake --build build_headless -j4
./build_headless/demo64k --headless --duration 30
```
See `doc/HEADLESS_MODE.md`.

### Size Measurement
```bash
./scripts/measure_size.sh
```
Measures demo vs external library size. See `doc/SIZE_MEASUREMENT.md`.

---

## Testing

### Run All Tests
```bash
cmake -B build -DDEMO_BUILD_TESTS=ON
cmake --build build -j4
cd build && ctest
# OR: make run_all_tests
```

### Run Subsystem Tests
```bash
make run_audio_tests    # Audio system tests
make run_gpu_tests      # GPU/shader tests
make run_3d_tests       # 3D rendering tests
make run_assets_tests   # Asset system tests
make run_util_tests     # Utility tests
```

### Run Specific Test
```bash
./build/test_synth
```

---

## Training

### Patch-Based (Recommended)
Extracts patches at salient points, preserves natural pixel scale:
```bash
# Train with 32×32 patches at detected corners/edges
./training/train_cnn.py \
  --input training/input/ --target training/output/ \
  --patch-size 32 --patches-per-image 64 --detector harris \
  --layers 3 --kernel_sizes 3,5,3 --epochs 5000 --batch_size 16 \
  --checkpoint-every 1000
```

**Detectors:** `harris` (default), `fast`, `shi-tomasi`, `gradient`

### Full-Image (Legacy)
Resizes to 256×256 (distorts scale):
```bash
./training/train_cnn.py \
  --input training/input/ --target training/output/ \
  --layers 3 --kernel_sizes 3,5,3 --epochs 10000 --batch_size 8 \
  --checkpoint-every 1000
```

### Export & Validation
```bash
# Generate shaders from checkpoint
./training/train_cnn.py --export-only checkpoints/checkpoint_epoch_5000.pth

# Generate ground truth for comparison
./training/train_cnn.py --infer input.png \
  --export-only checkpoints/checkpoint_epoch_5000.pth \
  --output ground_truth.png
```

**Kernel sizes:** 3×3 (36 weights), 5×5 (100 weights), 7×7 (196 weights)

---

## Timeline

Edit `workspaces/main/timeline.seq`:
```text
SEQUENCE 0.0 0
  EFFECT + HeptagonEffect 0.0 60.0 0
```
Rebuild to apply. See `doc/SEQUENCE.md`.

---

## Audio

```cpp
#include "audio/audio_engine.h"

audio_init();
static AudioEngine g_audio_engine;
g_audio_engine.init();
g_audio_engine.update(music_time);
g_audio_engine.shutdown();
audio_shutdown();
```
See `doc/TRACKER.md` for music system.

---

## Assets

Edit `workspaces/main/assets.txt`, then rebuild:
```bash
cmake --build build -j4
```
See `doc/ASSET_SYSTEM.md` and `doc/WORKSPACE_SYSTEM.md`.

---

## CNN Testing

### Offline Shader Validation

**Note:** Tool builds and runs but produces incorrect output. Use CNNEffect visual validation in demo. See `doc/CNN_TEST_TOOL.md`.

```bash
# Test trained CNN on PNG input
./build/cnn_test input.png output.png

# Adjust blend amount (0.0 = original, 1.0 = full CNN)
./build/cnn_test input.png output.png --blend 0.5

# PPM output format
./build/cnn_test input.png output.ppm --format ppm
```

### Ground Truth Comparison
```bash
# Generate Python ground truth
./training/train_cnn.py --infer input.png \
  --export-only checkpoints/checkpoint_epoch_1000.pth \
  --output ground_truth.png

# Run tool
./build/cnn_test input.png tool_output.png

# Compare (Python required)
python3 -c "
import numpy as np
from PIL import Image
gt = np.array(Image.open('ground_truth.png').convert('RGB'))
out = np.array(Image.open('tool_output.png').convert('RGB'))
mse = np.mean((gt.astype(float) - out.astype(float)) ** 2)
print(f'MSE: {mse:.4f} (target: < 10.0)')
"
```

See `doc/CNN_TEST_TOOL.md` for full documentation.

---

## Modifying Build System

- **Add build option:** Edit `cmake/DemoOptions.cmake`
- **Add source files:** Edit `cmake/DemoSourceLists.cmake`
- **Add test:** Edit `cmake/DemoTests.cmake`
- **Add tool:** Edit `cmake/DemoTools.cmake`
- **Add library:** Edit `cmake/DemoLibraries.cmake`

See `doc/CMAKE_MODULES.md` for full architecture and shared macros.

---

## Additional Documentation

- **Build System:** `doc/BUILD.md` - Multi-platform, size optimization
- **CMake Modules:** `doc/CMAKE_MODULES.md` - Module architecture, shared macros
- **Tools:** `doc/TOOLS_REFERENCE.md` - spectool, coverage, Windows cross-compile
- **Shaders:** `doc/SEQUENCE.md` - Timeline format, shader parameters
- **3D:** `doc/3D.md` - Hybrid rendering, scene format
- **Hot Reload:** `doc/HOT_RELOAD.md` - Debug file watching