Jim RB

@jbohnslav.bsky.social

computer vision + machine learning. Perception at Zoox. Prev: Cobot, PhD. Arxiv every day.

ZEBRA-CoT Dataset for vision-language reasoning where the model *generates images during the CoT*. Example: for geometry problems, it's helpful to draw lines in image space. 182K CoT labels: math, visual search, robot planning, and more. Only downside: cc-by-nc license :(

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Franca Fully open vision encoder. Masks image, encodes patches, then trains student to match teacher's clusters. Key advance: Matryoshka clustering. Each slice of the embedding gets its own projection head and clustering objective. Fewer features == fewer clusters to match.

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VRU-Accident New benchmark of 1K videos, 1K captions, and 6K MCQs from accidents involving VRUs. Example: "why did the accident happen?" "(B): pedestrian moves or stays on the road." Current VLMs get ~50-65% accuracy, much worse than humans (95%).

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BlindSight AMD paper: they find attention heads often have stereotyped sparsity patterns (e.g. only attending within an image, not across). They generate sparse attention variants for each prompt. Theoretically saves ~35% FLOPs for 1-2% worse on benches.

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Long-RL Nvidia paper scaling RL to long videos. First trains with SFT on a synthetic long CoT dataset, then does GRPO with up to 512 video frames. Uses cached image embeddings + sequence parallelism, speeding up rollouts >2X. Bonus: code is already up!

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Skywork-R1V3: new reasoning VLM with 76% MMMU. InternViT-6B stitched with QwQ-32B. SFT warmup, GRPO on math, then a small SFT fine-tune at the end. Good benches, actual ablations, and interesting discussion. Details: 🧵

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MGPO: multi-turn grounding-based policy optimization. I've been waiting for a paper like this! Trains the LLM to iteratively crop regions of interest to answer a question, and the only reward is the final answer. Details in thread 👇

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DriveMRP: interesting method to get a VLM to understand BEV maps + driving scenarios They synthesize high-risk scenes derived from NuPlan. They render it as both a bird's eye view image and a front camera view. 👇

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SeqGrowGraph Instead of segment + postprocess, generate lane graphs autoregressively. Node == vertex in BEV space, edge == control point for Bezier curves. At each step, a vertex is added and the adjacency matrix adds one row + column. They formulate this process as next token prediction. Neat!

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GLM-4.1V-Thinking: new reasoning VLM with heavy emphasis on RL. Tons of hints but few ablations 😞 eg they upweight difficult-but-learnable samples every iteration, but don't show how it compares to baseline. 9B variant beats Qwen2.5-VL-7B on many standard benchmarks. Details in thread 👇

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DenseWorld-1M: insanely detailed + grounded caption dataset. Synthetic data only: SAM, APE for segmentation. Each crop is captioned and verified. VLMs stitch object captions into huge image captions. Beats Sa2VA on referring expression segmentation. Dataset improves Qwen2.5-VL on VQA benchmarks

DenseWorld-1M: Towards Detailed Dense Grounded Caption in the Real World

Multimodal Large Language Models (MLLMs) demonstrate a complex understanding of scenes, benefiting from large-scale and high-quality datasets. Most existing caption datasets lack the ground locations ...

arxiv.org

SAM4D: promptable 4D seg Data engine uses Grounding-Dino + SAM2 for segmentation + tracking in images. Lidar -> voxels -> ray casting to match to pixels. Clustering to stitch visual masklets into 3D instances. Model is like SAM2 but with a lidar encoder + motion-aware cross attention.

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MiCo: multi-image contrast Simple idea: Input is multiple augmented images, either from video or image edits. Prompt: "are these images the same or different?" Train with GRPO. Large bump in multi-image benchmarks, minor bump in general VQA / hallucination benches.

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SpatialReasoner-R1 Generates long CoT data with Multi-Model Monte Carlo Tree Search -- multiple candidate models for each step, evaluated by multiple LLM judges. DPO with separate losses on the "descriptive" caption and reasoning. Huge improvements on spatial datasets, good performance on VQA.

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ScaleCap: synthetic image captioning pipeline. 2542 characters per cap. Given a caption, generates followup questions and answers with a VLM. Compute P(sentence | image,prompt) - P(sentence|prompt). Sentences with low scores are only using their text prior, so filter them out.

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UniVLA: VQA, world modeling, and robotic controls all-in-one transformer VQ-quantize images, DCT robotic actions, standard text tokens. Train the whole interleaved sequence with NTP. This type of approach would benefit from serious scaling. Anyone have a few thousand H100s laying around?

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ST-Kit: new dataset + benchmark for kinematic understanding for VLMs. Examples: estimate the total distance covered by <object> in the video? In what direction does <object> move in BEV coordinates? Open source and closed source models do poorly but their fine-tune does well.

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Vision-R1: another RLVR for VLMs, this time for detection. Rewards: formatting, precision, recall. Adds +9mAP to Qwen-2.5-VL on COCO + ODINW 🤯. They change the threshold in a curriculum (easy -> hard) which adds ~2 points. Repo has training code based on R1-V and TRL 👍

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CAR-1000 Move over Stanford Cars, new dataset with 1000 hierarchical classes and 140,312 samples! Scraped from a Chinese car enthusiast forum, there's a wide variety of cars from around the world.

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NuPlanQA: uses nuPlan annotations + GPT4o to 1 million QA pairs for training and an 8K multiple-choice benchmark. BEV-LLM: baseline model. Multi-view video -> BEVFusion -> cross-attend with image features -> projector -> LLaMA3.2. Some helpful ablations on # views and frames.

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Hydra-NeXt: strong E2E closed-loop driving performance with only open-loop training Images -> encoder -> 4096 discrete trajectory vocab -> transformer -> bicycle model -> denoising diffusion refinement -> best trajectory selection. Much better closed-loop perf than UniAD, VAD

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Nice methods paper (/ advertisement) from Nvidia on training video models with NeMo. Nuts and bolts: use Ray + NVDEC for curation, S3 + WebDataset for dataloading, FSDP + TP + Context Parallelism + PP for video DiT training. 48.2% MFU

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ChatBEV: new dataset + benchmark for VQA on BEV maps for autonomous driving. Data from nuPlan. 116K train, 21K test. Render a BEV map + generate VQA with LLMs(?) Applications: VQA, use the model to condition a scene generator.

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TrajHF: diffusion-based planner fine-tuned with RLHF. Simple idea: humans have preferences for candidate trajectories. Collect human feedback on key frames from 4.5K clips mined for aggressive maneuvers. Improves these aggressive scenarios but worsens some open-loop metrics.

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DriveLMM-o1: new dataset + benchmark for autonomy VQA. Dataset is 18k QA pairs, each with step-by-step reasoning. Generated with GPT4o and human verified. Model is a fine-tuned InternVL2.5-8b. Nit: don't call your model o1 if you don't use RLVR!

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SimLingo: Wayve paper on VLAs for self driving Front camera + prompts -> InternVL2-0.5B. They add GPS targets with an MLP. Output language, and decode queries for waypoints + speed. Very strong CARLA performance, but CARLA-only training data.

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DeCapBench: new benchmark on super-detailed captioning. DCScore: new evaluation method for captioning, great correlation with human ratings. FeedQuill: VLM trained using PPO with a DScore-trained reward model. Great captioning specialist.

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DriveTransformer: E2E driving with a single (complex) transformer, not modular like UniAD. Beats UniAD, VAD in open-loop but by much more in closed-loop in CARLA. It's also more robust to camera perturbations.

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CLIPGrader: fine-tune CLIP to evaluate detection labels. Draw a magenta bbox on an image. Artificially perturb the box and make the caption "the magenta bounding box is a bad bounding box of a..." 91% accuracy in quality classification. Examples show lots of promise.

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AlphaDrive: Trains a reasoning VLM to output multiple discrete action plans (accelerate, turn left) for autonomous driving. Much better than zero-shot or SFT on MetaAD, a new dataset of 110K 3s clips. In ablations, SFT < RL < SFT + RL. Looks like the days of pure SFT are over!

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