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PGT: Procedurally Generated Tasks for improving visual grounding in MLLMs
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Proposes PGT, procedurally generated geometric-overlay QA tasks added to existing training images, which improve spatial, counting and 3D/depth understanding in MLLMs without degrading general perception.
Problem
MLLMs struggle with fine-grained spatial relational, quantitative and depth understanding, often relying on linguistic priors and dataset shortcuts rather than grounded visual geometry.
Approach
Overlay unambiguous geometric primitives (colored bounding boxes, semi-transparent circles, labeled points) on existing training images and procedurally generate QA pairs about them, so that the model must ground in visual geometry without language shortcuts; the overlay augments existing samples without increasing dataset size, and the skills transfer to real-world relational and 3D/depth benchma
Key results
- Instruction tuning Llama-3-8B with PGT raises What's Up from 77.8 to 97.4 (+19.6) and CV-Bench-2D from 58.5 to 71.8 (+13.3), with CV-Bench-3D up +9.7.
- Finetuning LLaVA-Next-7B with 5k PGT samples gives +8.3 on CV-Bench-2D, +6.2 on VSR and +14.9 on TallyQA.
- Finetuning Qwen2.5-VL-3B with PGT yields +7.8 on CV-3D-related depth gains, comparable to a +8.4 gain from a real-data Specialized Mix of the same size.
Surprising findings
- Skills learned from abstract 2D geometric overlays transfer to 3D/relative depth estimation on real images, with removing the distance task dropping 3D/Depth score from 70.9 to 61.7.
- Overlaying PGT on existing real images performs nearly as well as training on separate synthetic data while keeping the sample count unchanged.
Limitations
- Task suite is a proof-of-concept; authors acknowledge it is not exhaustive and extensions (3D primitives, temporal, multi-step) are left to appendix.
- Injecting more than two PGT tasks per image degrades 3D/depth performance and risks visual clutter.
- Gains on some general benchmarks are mixed (e.g., GQA and POPE slight declines for some backbones).
Experimental setup
Datasets: LLaVA-v1.5-Instruct Cambrian-7M TallyQA VSR Spatial-Ladder-26k
Benchmarks: What's Up CV-Bench-2D VSR CV-Bench-3D TallyQA MMVP RealWorldQA BLINK MMSTAR GQA POPE SEED
Metrics: accuracy
Baselines: LLaVA-Next-7B InternVL3-8B Qwen2.5-VL-3B Qwen2.5-VL-7B ViGoRL-3B Spatial-Ladder-3B ThinkLite-VL Specialized Mix
Builds on: LLaVA-v1.5 Prismatic training framework LoRA
Closest papers by meaning
- DiG: Differential Grounding for Enhancing Fine-Grained Perception in Multimodal Large Language Models (CVPR 2026 · similarity 0.91)
- GroundingME: Exposing the Visual Grounding Gap in MLLMs through Multi-Dimensional Evaluation (CVPR 2026 · similarity 0.90)
- Perception Tokens Enhance Visual Reasoning in Multimodal Language Models (CVPR 2025 · similarity 0.90)
- Learning to See Before Seeing: Demystifying LLM Visual Priors from Language Pre-training (ICLR 2026 · similarity 0.90)
- SIFThinker: Spatially-Aware Image Focus for Visual Reasoning (AAAI 2026 · similarity 0.90)
- Visual Jigsaw Post-Training Improves MLLMs (ICLR 2026 · similarity 0.90)
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