FishServer/FishMeasure/measure

Fish Weight Prediction using PointNet++

This module uses PointNet++ to predict fish weight from partial point cloud data.

Overview

We provide two approaches for fish weight prediction:

Approach 1: Direct Regression (Original)

Directly predict the absolute weight from a single point cloud.

Approach 2: Comparison-Based (Recommended)

Predict the weight difference between two point clouds. For a new fish:

1. Find the closest reference fish by length (from known dataset)
2. Predict weight difference using the trained model
3. Calculate: new_weight = reference_weight + predicted_difference

Why comparison-based?

• Relative comparisons are often more accurate than absolute predictions
• Leverages known reference data
• More robust to incomplete/partial point clouds
• Better performance with small datasets (~100 samples)

Workflow

Approach 1: Direct Regression

1. Dataset Preparation (dataset.py): Prepare training data from multiple point clouds
2. Training (train_weight_regression.py): Train PointNet++ model for weight regression
3. Testing/Inference (test_weight_regression.py): Test the trained model on new point clouds

Approach 2: Comparison-Based (Recommended)

1. Dataset Preparation (dataset.py): Same as Approach 1
2. Training (train_weight_comparison.py): Train PointNet++ model to predict weight differences
3. Testing/Inference (test_weight_comparison.py): Test using reference dataset

Dataset Preparation

The dataset.py script processes point clouds from an input folder:

• Input: Folder containing multiple point cloud subfolders (e.g., output_preview/xxxx/cloud/)
• Process:
  1. For each subfolder, find all PLY files
  2. Select the point cloud with the largest length (max x - min x)
  3. Normalize the point cloud by moving it to the center of origin (centroid = 0)
  4. Save the normalized PLY file and corresponding weight label to the output folder

Usage:

python3 measure/dataset.py --input /path/to/pointclouds --labels /path/to/labels.csv --output /path/to/dataset

Label CSV Format:

subfolder_name,weight
HD1080_SN43186771_16-41-37,0.5
HD1080_SN43186771_16-41-40,0.6
...

Training

The train_weight_regression.py script trains a PointNet++ model for weight regression:

• Model: PointNet++ (SSG - Single Scale Grouping) adapted for regression
• Data Augmentation (for 150 samples):
  • Random point sampling (different number of points)
  • Random rotation around z-axis
  • Random scaling (small variations)
  • Random jitter (noise)
  • Random point dropout

Usage:

python3 measure/train_weight_regression.py \
    --data_path /path/to/dataset \
    --batch_size 16 \
    --num_point 1024 \
    --epoch 200 \
    --learning_rate 0.001

Testing/Inference

The test_weight_regression.py script performs inference on new point clouds:

Usage:

# Test on a single point cloud
python3 measure/test_weight_regression.py \
    --model /path/to/checkpoint.pth \
    --ply /path/to/pointcloud.ply

# Test on a folder of point clouds
python3 measure/test_weight_regression.py \
    --model /path/to/checkpoint.pth \
    --folder /path/to/pointclouds \
    --output results.json

Comparison-Based Approach (Recommended)

Training

Train a model to predict weight differences between point cloud pairs:

python3 measure/train_weight_comparison.py \
    --data_path /path/to/dataset \
    --reference_folder /path/to/reference/dataset \
    --batch_size 8 \
    --num_point 1024 \
    --epoch 200 \
    --learning_rate 0.001 \
    --pair_strategy random  # or 'length_based'

Pair Strategies:

• random: Random pairs (more diverse training)
• length_based: Pair based on similar lengths (more realistic comparisons)

Testing

For a new fish point cloud, find the closest reference and predict weight difference:

# Test on a single point cloud
python3 measure/test_weight_comparison.py \
    --model /path/to/checkpoint.pth \
    --reference_folder /path/to/reference/dataset \
    --ply /path/to/new_fish.ply

# Test on a folder of point clouds
python3 measure/test_weight_comparison.py \
    --model /path/to/checkpoint.pth \
    --reference_folder /path/to/reference/dataset \
    --folder /path/to/new_fishes \
    --output results.json

How it works:

1. Loads all reference point clouds (with known weights and lengths)
2. For each new fish, finds the closest reference by length
3. Predicts weight difference: predicted_diff = model(reference_pc, new_pc)
4. Calculates weight: new_weight = reference_weight + predicted_diff

File Structure

measure/
├── README.md                      # This file
├── dataset.py                     # Dataset preparation script
├── train_weight_regression.py     # Direct regression training
├── test_weight_regression.py       # Direct regression inference
├── train_weight_comparison.py      # Comparison-based training
├── test_weight_comparison.py       # Comparison-based inference
├── pointnet2_regression.py         # Direct regression model
├── pointnet2_comparison.py         # Comparison model
├── data_loader.py                  # Direct regression data loader
├── data_loader_comparison.py       # Comparison data loader
└── data/                           # Data folder (for OCR results, etc.)

Notes

• Direct Regression: Predicts absolute weight from a single point cloud
• Comparison-Based: Predicts weight difference between two point clouds (recommended for small datasets)
• Point clouds are normalized to the origin before training/inference
• Data augmentation is crucial given the small dataset size (~100-150 samples)
• The comparison model uses shared PointNet++ encoder for both point clouds, then concatenates features