# Pixel-Based Maze Evaluation (Pure Vision)

Pure computer vision-based evaluation for maze-solving generation tasks. Compares generated maze solutions against ground-truth solution images using pixel-level analysis — no VLMs/LLMs involved.

| Script | Input | What it evaluates |
|--------|-------|-------------------|
| `image_gen_evaluation.py` | PNG images | Whether a generated maze-solution **image** is correct (blue path vs solution) |
| `video_gen_evaluation.py` | MP4 videos | Whether a generated maze-solution **video** is correct (green marker trajectory vs solution) |

The video script works by:
1. Extracting frames from the generated video (default: 192 frames @ 24fps)
2. Tracking the green marker position across all frames to form the generated path
3. Comparing the accumulated path with the reference solution image

## Installation

```bash
pip install opencv-python numpy pillow scipy scikit-image
```

## Usage

### Image Evaluation

```bash
# Evaluate a single image
python image_gen_evaluation.py --single "/path/to/generated_image.png"

# Evaluate an entire directory (default model: nano_banana_pro)
python image_gen_evaluation.py --model_name nano_banana_pro

# Custom directories
python image_gen_evaluation.py \
  --input_dir "/path/to/generated/images" \
  --solution_dir "/path/to/solution/images" \
  --output_dir "/path/to/output/results" \
  --model_name my_model
```

### Video Evaluation

```bash
# Evaluate a single video
python video_gen_evaluation.py --single "/path/to/generated_video.mp4"

# Evaluate an entire directory (default model: veo3)
python video_gen_evaluation.py --model_name veo3

# Custom directories
python video_gen_evaluation.py \
  --input_dir "/path/to/generated/videos" \
  --solution_dir "/path/to/solution/images" \
  --output_dir "/path/to/output/results" \
  --model_name my_model

# Specify number of frames to extract
python video_gen_evaluation.py --num_frames 192

# Loop through round directories
for dir in /path/to/video_results/veo3/dfs/easy_round*; do
    python video_gen_evaluation.py --input_dir "$dir" --model_name veo3
done
```

### Batch Evaluation (All Algorithms / Difficulties / Rounds)

To evaluate a model across all maze algorithms (`dfs`, `wilson`), difficulty levels (`easy`, `medium`, `hard`), and generation rounds, run from this directory:

```bash
BASE_DIR=/path/to/maze_solving_task   # contains image_results/, video_results/, data/solution/

# Images (e.g. gpt_image_1.5; also: nano_banana, nano_banana_pro, qwen_image)
for round in 1 2 3; do
    for algo in dfs wilson; do
        for difficulty in easy medium hard; do
            python image_gen_evaluation.py \
                --input_dir ${BASE_DIR}/image_results/gpt_image_1.5/${algo}/${difficulty}_round${round} \
                --solution_dir ${BASE_DIR}/data/solution \
                --model_name gpt_image_1.5
        done
    done
done

# Videos (e.g. wan2.2; also: veo3, sora2)
for round in 1 2 3 4 5; do
    for algo in dfs wilson; do
        for difficulty in easy medium hard; do
            python video_gen_evaluation.py \
                --input_dir ${BASE_DIR}/video_results/wan2.2/${algo}/${difficulty}_round${round} \
                --solution_dir ${BASE_DIR}/data/solution \
                --model_name wan2.2
        done
    done
done
```

Adjust the model name and round range to match what was generated.

### Default Paths

When flags are omitted, the scripts fall back to these defaults:

| Flag | Default | Relative to |
|------|---------|-------------|
| `--input_dir` | `./image_results/<model_name>` or `./video_results/<model_name>` | current working directory |
| `--solution_dir` | `./data/solution` | current working directory |
| `--output_dir` | `../evaluation_results/pixel_based_evaluation/<image\|video>_evaluation_results/<model_name>` | current working directory |

Unless you run the scripts from a directory that contains `image_results/`/`video_results/` and `data/solution/`, pass `--input_dir` and `--solution_dir` explicitly (as in the batch examples above).

**Note**: for sora2 models (`--model_name` containing `sora`), the video script automatically extracts 360 frames (12s @ 30fps) instead of the default 192, unless `--num_frames` is set to a non-default value.

## Video Path Extraction Methods

### 1. Green Marker Tracking (Default)

`--extraction_method green_marker_tracking`

- Tracks the position of the green marker in each frame
- Accumulates all green marker positions to form the generated path
- Works well when the video shows a moving green marker tracing the solution

### 2. Frame Differencing

`--extraction_method frame_differencing`

- Uses frame-to-frame differences to detect marker movement
- Detects new green pixels that appear between consecutive frames
- Alternative method for videos with different marker behaviors

## Evaluation Metrics

### 1. Wall Crossing Detection

**Purpose**: Detect if the generated path crosses black walls (invalid move)

**Method**:
- **Image**: Extract blue path and black wall pixels from the generated image; apply 3px erosion tolerance (handles anti-aliasing); flag as crossing only if ratio > 1%
- **Video**: Accumulate the path from all frames; check against the **solution's** wall structure (not video frame walls); apply significant erosion (1/4 cell size) to only detect interior crossing; use raw path (no dilation) to avoid false positives at edges; flag only if ratio > 5%

**Output**:
- `wall_crossing_detected`: Boolean
- `wall_crossing_pixels`: Number of crossing pixels
- `wall_crossing_ratio`: Fraction of path crossing walls

### 2. Layout Matching

**Purpose**: Verify maze structure and marker positions match the solution

**Method**:
- Compare black wall regions using IoU
- Compare green square (start) and red square (end) centroid positions
- **Image**: single image check, position tolerance 20 pixels
- **Video**: layout is checked for EACH frame (parallelized with ThreadPoolExecutor) and the **minimum** score across all frames is reported (worst-case detection); position tolerance 50 pixels (video resolution differences)

**Output**:
- `layout_match_score`: Combined score, 0-1 (video: minimum across frames)
- `maze_structure_iou`: Wall structure IoU (video: at worst frame)
- `green_position_match` / `red_position_match`: Boolean
- `green_centroid_distance` / `red_centroid_distance`: Distance in pixels

### 3. Path Matching (Dilate + IoU)

**Purpose**: Compare the generated path with solution blue cells

**Challenge**: The generated path is thin (a blue line in images, a marker trajectory in videos) while solutions have filled blue cells

**Method**:
- **Image**: dilate the thin generated blue line to match cell width
- **Video**: dilate the accumulated green marker path to match cell width
- Compute IoU with solution blue regions, plus precision and recall

**Output**:
- `path_match_iou`: Intersection over Union
- `path_precision`: Fraction of generated path that's correct
- `path_recall`: Fraction of solution path that's covered (pixel-level)
- `target_achievement`: Fraction of solution cells touched by generated path (cell-level, 0-1)
  - More lenient than recall: counts a cell as "achieved" if generated path touches it at all
  - Better reflects route correctness when generated path is thinner than solution cells

### 4. Reflection/Exploration Detection

**Purpose**: Detect if the model shows reasoning behavior (backtracking, exploration)

**Method**:
- Skeletonize the generated path and trace it
- Detect loops (cells visited multiple times)
- Compare path length vs solution path length
- Flag reflection if loops exist OR path is >1.3x longer

**Output**:
- `has_reflection`: Boolean
- `loop_count`: Number of detected loops
- `path_length_ratio`: Generated length / Solution length
- `exploration_score`: Combined exploration metric (0-1)

### 5. Gated Metrics (Video Only, Binary Pass/Fail)

**Purpose**: Provide strict pass/fail criteria for evaluation

**Criteria**:
| Metric | Condition |
|--------|-----------|
| `layout_match_score_gated` | 1 if `maze_structure_iou > 0.8`, else 0 |
| `target_achievement_gated` | 1 if `target_achievement > 0.95`, else 0 |
| `overall_score_gated` | 1 if ALL three conditions are met, else 0 |

**Overall Score Gated Requirements** (all must be true):
1. `layout_match_score_gated == 1` (maze structure IoU > 0.8)
2. `wall_crossing_detected == False` (no wall crossing)
3. `target_achievement_gated == 1` (target achievement > 0.95)

### Video-Specific Metrics

- `total_frames`: Total number of frames extracted from video
- `frames_with_marker`: Number of frames where green marker was detected
- `path_extraction_method`: Method used for path extraction

## Overall Score Calculation

```
overall_score = layout_score * 0.2 + path_iou * 0.5 - wall_penalty

where:
  wall_penalty = 0.3 if wall_crossing_detected else 0.0
```

## Output Files

By default, results are written to `../evaluation_results/pixel_based_evaluation/` (relative to this directory). Override with `--output_dir`.

### Image Evaluation Results

```
../evaluation_results/pixel_based_evaluation/image_evaluation_results/<model_name>/
├── evaluation_results_<timestamp>.json    # Final results
├── evaluation_results_latest.json         # Latest results (overwritten)
├── evaluation_results_incremental.json    # Progress during evaluation
└── visualizations/                        # Visualization images
    └── <image_name>_evaluation.png
```

### Video Evaluation Results

```
../evaluation_results/pixel_based_evaluation/video_evaluation_results/<model_name>/
├── evaluation_results_<round>_<timestamp>.json    # Final results (with round suffix)
├── evaluation_results_<round>_latest.json         # Latest results (overwritten)
├── evaluation_results_<round>_incremental.json    # Progress during evaluation
├── <video_name>_<round>_result.json               # Individual video result
└── visualizations/                                # Visualization images
    └── <video_name>_<round>_evaluation.png
```

**Round suffix handling**: when evaluating directories with round information (e.g. `easy_round1`), the video script automatically extracts the round suffix from the input directory path and appends it to all output filenames (e.g. `_round1`), so results from different rounds can be distinguished.

### Visualization Layout

Each visualization is a 2x2 grid (top-left is the generated image, or the path accumulated from all video frames):

```
┌─────────────────┬─────────────────┐
│  Generated /    │  Solution       │
│  Video Path     │  (reference)    │
├─────────────────┼─────────────────┤
│  Wall Crossing  │  Path Compare   │
│  Overlay        │  Overlay        │
└─────────────────┴─────────────────┘
```

**Color Legend (Path Compare)**:
- Green: Solution path only (missed by generated)
- Red: Generated path only (extra exploration)
- Yellow: Overlap (correct path)

**Color Legend (Wall Crossing)**:
- Yellow: Actual wall crossing (counted)
- Image: Orange = edge touch (tolerated, not counted)
- Video: Light blue = valid path (not crossing walls)

## File Naming Convention

| | Pattern | Example |
|---|---------|---------|
| Generated image | `{algo}_{difficulty}_{size}_n{idx}_{variant}_targeted_solution.png` | `dfs_easy_3x3_n000_var1_fixed_both_targeted_solution.png` |
| Generated video | `{algo}_{difficulty}_{size}_n{idx}_{variant}.mp4` | `dfs_easy_3x3_n000_var1_fixed_both.mp4` |
| Solution image | `{algo}_{difficulty}_{size}_n{idx}_{variant}_solution.png` | `dfs_easy_3x3_n000_var1_fixed_both_solution.png` |

## Example Output

Video evaluation result (image results contain the same fields minus the video-specific and gated ones):

```json
{
  "filename": "dfs_easy_3x3_n000_var1_fixed_both.mp4",
  "solution_file": "dfs_easy_3x3_n000_var1_fixed_both_solution.png",
  "wall_crossing_detected": false,
  "wall_crossing_pixels": 0,
  "wall_crossing_ratio": 0.0,
  "layout_match_score": 0.988,
  "maze_structure_iou": 0.85,
  "green_position_match": true,
  "red_position_match": true,
  "path_match_iou": 0.369,
  "path_precision": 0.554,
  "path_recall": 0.525,
  "target_achievement": 0.98,
  "has_reflection": true,
  "loop_count": 20,
  "path_length_ratio": 1.95,
  "exploration_score": 1.0,
  "total_frames": 192,
  "frames_with_marker": 180,
  "path_extraction_method": "green_marker_tracking",
  "overall_score": 0.382,
  "layout_match_score_gated": 1,
  "target_achievement_gated": 1,
  "overall_score_gated": 1
}
```

**Gating example breakdown**:
- `maze_structure_iou = 0.85` → `layout_match_score_gated = 1` (0.85 > 0.8)
- `wall_crossing_detected = false` → passes wall crossing check
- `target_achievement = 0.98` → `target_achievement_gated = 1` (0.98 > 0.95)
- All three conditions met → `overall_score_gated = 1`

## Summary Statistics

After evaluating a directory, each script outputs aggregated statistics (gated/video-specific blocks appear for video evaluation only):

```json
{
  "summary": {
    "wall_crossing": {
      "count": 5,
      "rate": 0.05
    },
    "path_matching": {
      "mean_iou": 0.45,
      "std_iou": 0.15,
      "mean_precision": 0.62,
      "mean_recall": 0.71,
      "mean_target_achievement": 0.92
    },
    "layout_matching": {
      "mean_score": 0.95,
      "green_match_rate": 0.98,
      "red_match_rate": 0.97
    },
    "reflection": {
      "count": 42,
      "rate": 0.42
    },
    "overall": {
      "mean_score": 0.51,
      "std_score": 0.18,
      "min_score": 0.10,
      "max_score": 0.85
    },
    "gated_metrics": {
      "layout_match_score_gated_count": 80,
      "layout_match_score_gated_rate": 0.80,
      "target_achievement_gated_count": 75,
      "target_achievement_gated_rate": 0.75,
      "overall_score_gated_count": 70,
      "overall_score_gated_rate": 0.70
    },
    "video_specific": {
      "avg_frames_with_marker": 175.5
    }
  }
}
```

## Tuning Parameters

Image evaluation (`image_gen_evaluation.py`):

| Parameter | Default | Description |
|-----------|---------|-------------|
| `tolerance_pixels` | 3 | Wall erosion for edge tolerance |
| `min_crossing_ratio` | 0.01 | Min ratio to flag wall crossing |
| `position_tolerance` | 20.0 | Max centroid distance for position match |
| `dilation_size` | auto | Size to dilate thin lines (auto-detected) |

Video evaluation (`video_gen_evaluation.py`):

| Parameter | Default | Description |
|-----------|---------|-------------|
| `num_frames` | 192 | Number of frames to extract from each video |
| `min_crossing_ratio` | 0.05 | Min ratio to flag wall crossing (5%) |
| `position_tolerance` | 50.0 | Max centroid distance for position match |
| `wall_erosion` | cell_size/4 | Erosion applied to walls before crossing check |
| `dilation_size` | auto | Size to dilate paths (auto-detected from cell size) |
| `BLACK_THRESHOLD` | 30 | Grayscale threshold for wall detection |
| `WHITE_THRESHOLD` | 200 | Grayscale threshold for walkable path detection |

## Image vs Video Evaluation Differences

| Aspect | Image Evaluation | Video Evaluation |
|--------|-----------------|------------------|
| Input | PNG image files | MP4 video files |
| Path Source | Blue path in generated image | Accumulated green marker positions |
| Frame Processing | Single image | 192 frames per video |
| Layout Check | Single image check | Minimum score across ALL frames |
| Wall Reference | Solution's walls only | Solution's walls only |
| Position Tolerance | 20 pixels | 50 pixels |
| Parallel Processing | N/A | ThreadPoolExecutor for frames |
| Gated Metrics | N/A | Binary pass/fail (see above) |

## Comparison with VLM-based Evaluation

| Aspect | These Scripts (Vision) | VLM-based (Gemini) |
|--------|------------------------|-------------------|
| Speed | Fast (~0.5s/image, ~5-10s/video) | Slow (~5s/image, ~30s/video) |
| Cost | Free | API costs |
| Consistency | Deterministic | May vary |
| Interpretability | Pixel-level metrics | Natural language |
| Edge cases | May miss semantic issues | Better reasoning |

## Logging

Evaluation logs are saved to:
```
./evaluation_logs/
├── maze_vis_evaluation_<timestamp>.log          # image evaluation
└── maze_video_vis_evaluation_<timestamp>.log    # video evaluation
```