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Offroad Semantic Scene Segmentation

PyTorch · DINOv2 · OpenCV · Albumentations
Hackathon project — Duality AI Offroad Challenge (Team ORCA)


Model Architecture

Overview

Hybrid Transformer–CNN semantic segmentation model for off-road desert environments, trained on synthetic data from Duality AI's Falcon platform. Segments 10 terrain classes including rocks, vegetation, and navigable ground across challenging low-contrast scenes.


Architecture

Fused multi-depth DINOv2 (ViT) features with a manually constructed CNN feature pyramid neck to recover the spatial hierarchy that transformers lack natively.

  • Features extracted from early, mid, and final transformer blocks — capturing texture, object structure, and global semantics respectively
  • Pyramid levels at 9×9 → 72×72 built from the 36×36 token grid
  • Per-scale segmentation heads with deep supervision improve rare-class gradient flow and boundary sharpness

This bypasses the need for a conventional decoder by constructing spatial inductive bias explicitly from transformer patch tokens.


Loss & Training

Compound loss — CrossEntropy + Dice + Focal — to handle severe class imbalance across sparse terrain features (e.g., logs, flowers, rocks vs. dominant sky/landscape).

Hyperparameter Value
Input size 512×512
Optimizer AdamW
Learning rate 1e-4
Batch size 8

Augmentation pipeline (Albumentations): random crop, horizontal flip, brightness/contrast jitter, ImageNet normalization.


Results

Metric Value
Mean IoU (mIoU) ~0.70
Pixel Accuracy ~0.85
Inference Latency ~4 ms/image
Throughput ~200 FPS

Engineering

  • End-to-end training, evaluation, and checkpointing pipeline
  • Visualization tooling: segmentation overlays, per-class IoU plots, confusion matrices, input/GT/prediction comparisons
  • Latency benchmarking for deployment-readiness assessment
python train.py          # Training
python test.py           # Evaluation
python visualize_segmentation.py  # Qualitative results

Semantic Classes

ID Class
100 Trees
200 Lush Bushes
300 Dry Grass
500 Dry Bushes
550 Ground Clutter (walkable path — highlighted)
600 Flowers
700 Logs
800 Rocks
7100 Landscape
10000 Sky

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