MechVQA: Benchmarking and Enhancing Multimodal LLMs on Comprehensive Mechanical Drawing Understanding

Official code repository for the ICML 2026 paper "MechVQA: Benchmarking and Enhancing Multimodal LLMs on Comprehensive Mechanical Drawing Understanding".

If you use MechVQA, MechVL, or the released training and evaluation assets, please cite the paper. Machine-readable metadata are available in CITATION.cff.

🚧 Status: This repository is under active development. Inference code, the RL training framework, the public evaluation benchmark, the evaluation pipeline, the VQA-free data-generation pipeline, a compact SFT recipe, and a validated public VQA-only SFT train/validation release are available now. Model checkpoints and training data are released through ModelScope/HuggingFace links; additional internal training data are not included in this repository.

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📖 Introduction

Mechanical engineering drawings encode semantics through a compact, standardized graphical language — orthographic multi-view projections, dense dimensioning, section views, symbolic notations, and structured text. General Multimodal Large Language Models (MLLMs) remain brittle on them: high annotation density and weak domain priors, combined with unreliable spatial-relation reasoning under strict projection rules, make decisive cues easy to miss.

MechVQA bridges this gap with two contributions:

• 📊 MechVQA benchmark — the first comprehensive mechanical-drawing understanding dataset, built via a semi-automated construction and quality-control pipeline: 3.3K high-density drawings with 21K question–answer pairs, 10 fine-grained tasks across three capability levels — Recognition, Reasoning, and Judging.
• 🤖 MechVL model — a strong domain-specialized baseline built via a multi-stage training paradigm (SFT → two-stage self-play RL), reaching a Total score of 84.85 and outperforming the strongest closed-source MLLMs on MechVQA.

🏆 Highlights

Model	Recognition	Reasoning	Judging	Total
GPT-5	69.77	84.99	71.02	75.44
Gemini-3-Pro-Preview	76.74	87.74	77.28	77.28
GLM-4.6V (best closed-source)	88.37	86.68	78.91	78.91
MechVL-4B-SFT (Ours)	88.37	85.20	76.36	76.36
MechVL-4B-RL (Ours)	88.37	90.70	84.85	84.85

• MechVL-4B-RL achieves the best Total score (84.85), surpassing the strongest closed-source model (GLM-4.6V, 78.91) and all open-source MLLMs.
• On the hard subset, MechVL-4B-RL reaches 75%, beating the best closed-source model (Qwen3-VL-Plus, 66%) by +9 points.
• Ablations confirm DAPO > GRPO > GSPO, the value of two-stage self-play RL (81.95 → 84.85), and the necessity of all three reward terms.

See §6 of the paper for full tables and the 10 subtask definitions.

📰 Release Status

Component	Status
Inference scripts (SFT & RL, dual-mode)	✅ Ready
Self-contained example samples (10 QA + drawings)	✅ Ready
RL training framework (EasyR1/, sanitized)	✅ Ready
RL format prompt & reward functions	✅ Ready
MechVL-4B-SFT / -RL checkpoints	✅ Released (ModelScope full weights; HF mirroring in progress)
Public MechVQA evaluation benchmark (1,185 QA + drawings)	✅ Ready
Evaluation script & metrics	✅ Ready
VQA-free data-generation pipeline	✅ Ready
SFT recipe (LLaMA Factory 4B config + 20 examples)	✅ Ready
Public VQA-only SFT train/val release (13,515 QA + 3,371 images)	✅ Released (Hugging Face · ModelScope)
Additional internal training data	Not included

🗂️ Repository Structure

MechVQA/
├── ckpt/                # MechVL checkpoints (SFT & RL) — download separately, gitignored
├── scripts/
│   ├── batch_infer.py   # Inference entry: SFT/RL dual-mode (toggle MODE at top)
│   ├── modelscope_to_hf_dataset.py  # ModelScope-to-HF dataset mirror utility
│   └── README.md        # Inference usage (environment, params, outputs)
├── data/                # Built-in example samples (10 QA + 10 drawings)
├── benchmark_data/      # Public evaluation benchmark JSONL + packaged drawings
├── evaluation/          # OpenAI-compatible VQA evaluation pipeline
├── data_generation/     # Extract + VQA-free generation + QC + split scripts
├── training/            # LLaMA Factory SFT recipe, 4B config, public examples
├── prompts/
│   └── mech_r1.jinja    # RL format prompt (<think>/<answer> schema)
├── EasyR1/              # RL training framework (verl-based; GRPO/GSPO/DAPO/CISPO)
│   ├── verl/            # Core RL framework
│   ├── examples/        # mech_qwen3_vl_4b_*.sh training scripts + reward_function/ + format_prompt/
│   ├── scripts/         # Utilities (ray cluster, judge server, dataset download, model merge)
│   └── tests/ docs/
└── paper/               # Paper PDF

🔧 Environment

Inference (tested):

Dependency	Version
Python	3.10+
vLLM	0.11.0 (native qwen3_vl support)
transformers	4.57.1
torch	2.8.0+ (CUDA 12.x)
Pillow / jinja2 / tqdm	—

pip install "vllm>=0.11" "transformers>=4.57.1" pillow jinja2 tqdm

Training (EasyR1 / RL): see EasyR1/requirements.txt or use the provided EasyR1/Dockerfile.

Evaluation: see evaluation/requirements.txt.

Data generation: see data_generation/requirements.txt.

SFT recipe: see training/README.md.

🧠 Model Checkpoints

Place checkpoints under ckpt/ (gitignored due to size):

ckpt/
├── MechVQA_SFT/    # MechVL-4B-SFT  (Qwen3-VL-4B-Instruct, full-param SFT)
└── MechVQA_RL/     # MechVL-4B-RL   (DAPO two-stage self-play on top of SFT)

🤗 HuggingFace (checkpoints + paper): MechVQA Collection

🟣 ModelScope (full weights): MechVQA Collection

Download:

Model	HuggingFace	ModelScope (recommended, full weights)
MechVL-4B-SFT	XiaofengAlg/MechVL-4B-SFT	xiaofengalg/MechVL-4B-SFT
MechVL-4B-RL	XiaofengAlg/MechVL-4B-RL	xiaofengalg/MechVL-4B-RL

ModelScope repos contain the full checkpoints (all weights). HuggingFace repos currently hold configs + model card; the large weight files are being mirrored (HF mirror upload is bandwidth-limited) — use ModelScope for immediate access to the weights.

🚀 Quick Start: Inference

scripts/batch_infer.py runs vLLM inference for both SFT and RL models — toggle MODE at the top of the file:

MODE	Model	Prompt	Output
sft	ckpt/MechVQA_SFT	system prompt + image + question	free-form answer
rl	ckpt/MechVQA_RL	prompts/mech_r1.jinja rendered (no system)	<think>...</think><answer>...</answer>, <answer> extracted

From the repository root:

CUDA_VISIBLE_DEVICES=0 python scripts/batch_infer.py

• Runs on the built-in data/test_samples.jsonl (10 QA) by default — fully self-contained, no external data needed.
• Outputs outputs/{sft,rl}_infer_test.jsonl with GT vs prediction side-by-side.
• Supports resumable runs (skips already-succeeded samples), bad-image tolerance, incremental JSONL writing.
• See scripts/README.md for all configuration knobs.

📦 Public Benchmark Data

The public evaluation benchmark is packaged under benchmark_data/:

benchmark_data/
├── images/
└── vqa_benchmark/
    └── mechvqa_benchmark.jsonl

• mechvqa_benchmark.jsonl contains 1,185 QA records and 562 packaged drawing images.
• Image paths in each JSONL record are relative to benchmark_data/.
• Each record follows the public message schema:

{
  "messages": [
    {"role": "user", "content": "question text"},
    {"role": "assistant", "content": "reference answer"}
  ],
  "images": ["images/example.png"],
  "metadata": {
    "capability": "Reasoning",
    "subcategory": "Assembly Relationship",
    "difficulty": "Hard",
    "language": "中文"
  },
  "qualityscore": 1.0
}

Taxonomy labels in capability, subcategory, and difficulty use the English labels reported in the paper.

📦 Public SFT Training Data

The validated, VQA-only SFT train/validation release is hosted on both Hugging Face and ModelScope:

Platform	Dataset
Hugging Face	XiaofengAlg/MechVQA
ModelScope	xiaofengalg/MechVQA

The release contains 12,749 training records, 766 validation records, and 3,371 content-addressed images. It also includes the SHA-256 checksum manifest, release manifest, provenance records, and validation audit. The public package is scoped to VQA SFT data; additional internal training artifacts are not part of this release.

🏋️ Training (MechVL)

MechVL is trained in a multi-stage paradigm:

1. SFT stage — Initialize from Qwen3-VL-Instruct-4B, full-parameter SFT on the LLM module (vision encoder & projection frozen) over the MechVQA training split. Produces MechVL-4B-SFT (the reference policy π_ref).
2. RL stage — DAPO two-stage self-play:
   • Stage 2a (full): DAPO on the full training split.
   • Stage 2b (targeted): DAPO on a re-sampled subset with an increased proportion of underperforming subtasks.
   • Reward = Accuracy (LLM-as-a-Judge, semantic equivalence in [0,1]) + Format (binary, well-formed <think>/<answer>) + Quality (Logic / Professionalism / Conciseness, LLM-judge).

The RL pipeline is built on the included EasyR1/ (a verl-based framework). Example training scripts: EasyR1/examples/mech_qwen3_vl_4b_*.sh (covering GRPO / GSPO / DAPO / CISPO and the round-2 reward variants). Reward functions live in EasyR1/examples/reward_function/mech*.py.

The public SFT recipe is included under training/. It contains a vendored LLaMA Factory snapshot, one Qwen3-VL 4B full-parameter SFT config, and a compact 20-record example dataset for format verification:

cd training/LLaMA-Factory
pip install -e ".[torch,metrics]"
cd ../..

export MODEL_NAME_OR_PATH=/path/or/hf-id/to/qwen3-vl-4b-instruct
export DATASET_DIR=$PWD/training/LLaMA-Factory/data
export MEDIA_DIR=$PWD/training/LLaMA-Factory/data
export OUTPUT_DIR=/path/to/outputs/mechvqa_qwen3_vl_4b_full

bash training/run_sft.sh training/qwen3_vl_sft_4b_full_finetune.yaml

See training/README.md for the dataset registry and dry-run command. For the complete public VQA-only train/validation package, download XiaofengAlg/MechVQA from Hugging Face or xiaofengalg/MechVQA from ModelScope.

📊 Evaluation

MechVQA evaluates MLLMs across 10 fine-grained tasks grouped into three capability levels (Recognition / Reasoning / Judging), reported as per-level means and an overall Total score. See §3 and §6 of the paper for the task taxonomy, metrics, and full results.

The open-source evaluator is included under evaluation/. It runs target-model inference, judges responses with an OpenAI-compatible judge model, and reports aggregate and metadata-level metrics.

cd evaluation
pip install -r requirements.txt
cp configs/vqa_eval.example.json configs/vqa_eval.local.json
# Edit input_file, image_root, model names, API keys, and base URLs.
MAX_SAMPLES=5 bash scripts/run_all.sh configs/vqa_eval.local.json

See evaluation/README.md for the full two-phase workflow.

🏭 Data Generation

The public data-generation pipeline is included under data_generation/. It covers the open-source portion of the paper pipeline: drawing metadata extraction, VQA-free question generation from extracted metadata, model-based question checking, multi-answer generation with semantic voting, message-format conversion, difficulty assignment, and dataset splitting.

pip install -r data_generation/requirements.txt
python data_generation/extract_pipeline.py --help
python data_generation/generate_vqa_free_query.py --help

Internal/manual routes such as expert source curation, human metadata correction, template GT construction, 2D/3D candidate pairing, and CAD expert edits are intentionally not included.

📝 Citation

If you find MechVQA or MechVL useful in your research, please ⭐ star this repository and cite our paper:

@misc{kou2026mechvqabenchmarkingenhancingmultimodal,
      title={MechVQA: Benchmarking and Enhancing Multimodal LLMs on Comprehensive Mechanical Drawing Understanding},
      author={Qian Kou and Xiaofeng Shi and Yulin Li and Xiaosong Qiu and Xinyang Wang and Hua Zhou and Cao Dongxing},
      year={2026},
      eprint={2605.30794},
      archivePrefix={arXiv},
      primaryClass={cs.CV},
      url={https://arxiv.org/abs/2605.30794}
}

Plain-text citation

Qian Kou, Xiaofeng Shi, Yulin Li, Xiaosong Qiu, Xinyang Wang, Hua Zhou, and Cao Dongxing. 2026. MechVQA: Benchmarking and Enhancing Multimodal LLMs on Comprehensive Mechanical Drawing Understanding. arXiv:2605.30794. (Accepted to ICML 2026.)

APA 7th

Kou, Q., Shi, X., Li, Y., Qiu, X., Wang, X., Zhou, H., & Cao, D. (2026). MechVQA: Benchmarking and enhancing multimodal LLMs on comprehensive mechanical drawing understanding. arXiv. https://arxiv.org/abs/2605.30794

📄 License

This project is released under the Apache 2.0 License. The EasyR1/ RL framework retains its own license (see EasyR1/LICENSE).

🙏 Acknowledgements

MechVQA/MechVL are built on top of Qwen3-VL and the EasyR1/verl RL framework. We thank their contributors.

✉️ Contact

• Xiaofeng Shi — xfshi@baai.ac.cn
• Qian Kou — kouqian@baai.ac.cn

Beijing Academy of Artificial Intelligence (BAAI) · Institute of Information Engineering, CAS · Beijing University of Technology.

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