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INSID3: Training-Free In-Context Segmentation with DINOv3

<p align="center"> <a href="https://arxiv.org/abs/2603.28480"><img src="https://img.shields.io/badge/Paper-arXiv-red?style=flat-square&labelColor=444444" alt="Paper arXiv"></a> <a href=https://visinf.github.io/INSID3/><img src="https://img.shields.io/badge/Project-Page-1f6feb?style=flat-square&labelColor=444444" alt="Project Page"></a> </p>

Claudia Cuttano^1,2 · Gabriele Trivigno¹ · Christoph Reich^2,3,5,6 · Daniel Cremers^3,5,6 · Carlo Masone¹ · Stefan Roth^2,4,5

¹ Politecnico di Torino    ² TU Darmstadt    ³ TU Munich    ⁴ hessian.AI    ⁵ ELIZA    ⁶ MCML

✨ CVPR 2026 ✨

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INSID3 solves in-context segmentation entirely within a single frozen DINOv3 backbone:

🚀 Training-free: no fine-tuning, no segmentation decoder, no auxiliary models
🔍 Insight: we uncover and fix a positional bias in DINOv3 features, improving their reliability beyond segmentation
📈 State-of-the-art, smaller & faster: outperforms both training-free and specialized methods while using a single backbone
🌍 Generalizes broadly: from object-level to part-level and personalized segmentation, across natural, medical, underwater, and aerial domains

<p align="center"> <img src="assets/teaser.png"> </p>

⚙️ Environment Setup

INSID3 can be set up either with Conda or with uv. Choose one of the following options.

Option 1: Conda

To get started, create a Conda environment and install the required dependencies. The experiments in the paper were run with PyTorch 2.7.1 (CUDA 12.6), which we provide as a reference configuration.

To set up the environment using Conda, run:

conda create --name insid3 python=3.10 -y
conda activate insid3
pip install -r requirements.txt

Optional: If you want to use CRF-based mask refinement, also install:

git clone https://github.com/netw0rkf10w/CRF.git
cd CRF
python setup.py install
cd ..

Option 2: uv

As an alternative to Conda, you can use uv, a fast Python package and environment manager. In this setup, the optional CRF dependency is already included.

On macOS and Linux:

curl -LsSf https://astral.sh/uv/install.sh | sh

Then run:

# Ensure CUDA 12.6 is loaded beforehand
# This will automatically create a virtual environment (.venv) and install dependencies from pyproject.toml
uv sync
source .venv/bin/activate

🧱 DINOv3 Weights

INSID3 relies on a frozen DINOv3 backbone. Please download the pretrained weights from the official repository: 👉 https://github.com/facebookresearch/dinov3

Create the pretrain directory:

mkdir -p pretrain

Place the weights of the backbone you want to use in the pretrain/ folder:

pretrain/dinov3_vitl16_pretrain_lvd1689m-8aa4cbdd.pth
pretrain/dinov3_vitb16_pretrain_lvd1689m-73cec8be.pth
pretrain/dinov3_vits16_pretrain_lvd1689m-08c60483.pth

By default, we use the Large model (dinov3_vitl16_pretrain_lvd1689m-8aa4cbdd.pth).

📍 Minimal Usage

Here is a minimal example to segment a target image given a reference image and its mask:

from models import build_insid3

# Build model
model = build_insid3()

# Set reference and target
model.set_reference("path/to/ref_image.png", "path/to/ref_mask.png")
model.set_target("path/to/tgt_image.png")

# Predict
pred_mask = model.segment()  # (1024, 1024) bool

📦 Data

Please refer to docs/data.md for dataset preparation instructions.

🚀 Inference

Evaluate INSID3:

python inference.py --dataset coco --exp-name insid3-coco

Main arguments:

• --dataset: supported [coco, lvis, pascal_part, paco_part, isaid, isic, lung, suim, permis]

• --model_size: DINOv3 backbone size (small, base, large, default: large)

• --shots: number of reference images per episode (e.g., 1-shot, 5-shot, default: 1)

• Other args: hyperparameters (e.g., --tau, --merge-thresh, --svd-comps) have default values as in the paper; pass them to override the defaults. See opts.py.

Note: By default, the predicted mask is upsampled to the original image resolution using bilinear interpolation. For additional refinement, enable CRF-based refinement with --crf-mask-refinement.

💡 Why INSID3 Works

INSID3 builds on two key observations about DINOv3 features.

(i) Dense DINOv3 features naturally induce a structured decomposition of the scene. By clustering them, we obtain coherent object- and part-level regions without supervision.

<p align="center"> <img src="assets/clustering.png" alt="Dense DINOv3 features" width="80%"> </p>

(ii) Besides semantic matches, DINOv3 also responds to absolute image position. Given a patch on the bird’s tail in the reference image, the DINOv3 similarity map activates on (i) the tail in the target image, but also (ii) over the left portion of the image.

<p align="center"> <img src="assets/similarity_maps.png" alt="Dense DINOv3 features" width="55%"> </p>

PCA on low-semantic-content images reveals that this effect lives in a stable low-dimensional subspace. INSID3 removes it in a training-free way: we identify the positional component of DINOv3 features and project onto its orthogonal complement. This suppresses coordinate-driven responses while preserving semantics.

<p align="center"> <img src="assets/positional_subspace.png" alt="Dense DINOv3 features" width="80%"> </p>

Citation

If you find this work useful in your research, please cite:

@inproceedings{cuttano2026insid3,
  title     = {{INSID3}: Training-Free In-Context Segmentation with {DINOv3}},
  author    = {Claudia Cuttano and Gabriele Trivigno and Christoph Reich and Daniel Cremers and Carlo Masone and Stefan Roth},
  booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
  year      = {2026}
}

Acknowledgements

We gratefully acknowledge the contributions of the following open-source projects:

• DINOv3
• Matcher