Author: Denis Avetisyan
New research demonstrates how vision-language models can enable robots to accurately estimate the 3D position of objects using only standard RGB images.

This work presents a method for monocular 3D object position estimation leveraging vision-language models, achieving a median absolute error of 13mm and exploring open-set detection with low-rank adaptation.
Accurate 3D perception remains a key challenge for intuitive human-robot interaction, particularly when relying on limited visual input. This paper, ‘Monocular 3D Object Position Estimation with VLMs for Human-Robot Interaction’, investigates leveraging pre-trained Vision-Language Models (VLMs) to estimate the 3D position of objects from single RGB images, combined with natural language instructions and robot state information. By finetuning a VLM with a custom regression head and conditional routing, we achieve a median absolute error of 13mm on a novel, heterogeneous dataset of over 100,000 images-a five-fold improvement over non-finetuned baselines. Will this approach enable robots to more effectively understand and interact with their environments based on natural human guidance?
Decoding Spatial Relationships: The Challenge of 3D Perception
Effective robotic manipulation hinges on a robot’s ability to precisely locate objects in three-dimensional space, a task deceptively complex despite advancements in computer vision. While humans effortlessly perceive depth and distance, robots often struggle, particularly when relying on limited visual data – a single camera view, for instance. This challenge stems from the inherent ambiguity of translating a two-dimensional image into a three-dimensional understanding of the world; multiple objects can project onto the same retinal space, and cues for depth are often incomplete or obscured. Consequently, even simple tasks like grasping an object require sophisticated algorithms to infer spatial relationships and accurately determine an object’s position, orientation, and distance – capabilities that remain a central focus of robotics research.
Determining an object’s distance and location using a single camera – monocular vision – presents a fundamental challenge for robotics due to the loss of depth information. Unlike human vision, which integrates cues from two eyes, a single image inherently lacks the parallax needed to directly calculate depth. Consequently, robotic systems are increasingly reliant on sophisticated vision-language models that leverage contextual understanding and learned associations to infer three-dimensional positioning. These models analyze visual features in conjunction with linguistic data, essentially ‘reasoning’ about the likely depth and spatial relationships based on prior knowledge and scene understanding. The success of this approach hinges on the model’s ability to resolve ambiguities and accurately estimate object positions, even with partial or obscured views – a task demanding both computational power and robust training datasets.
Despite advancements in computer vision, pinpointing the precise 3D location of objects remains a bottleneck for real-time robotic systems. Existing models, while demonstrating impressive accuracy in controlled settings, often struggle with the computational demands of processing visual data quickly enough for dynamic environments. This limitation stems from the intensive calculations required to translate 2D images into a comprehensive 3D understanding, hindering a robot’s ability to react and manipulate objects with the necessary speed and dexterity. Consequently, researchers are actively exploring innovative approaches – including more efficient neural network architectures and sensor fusion techniques – to enhance both the precision and processing speed of 3D object position estimation, ultimately bridging the gap between theoretical capability and practical robotic implementation.
Bridging the Semantic Gap: Vision-Language Models as Spatial Interpreters
Vision-Language Models (VLMs) address limitations in traditional 3D perception systems by integrating natural language processing with computer vision. Conventional methods often struggle with ambiguity and require precise object definitions, whereas VLMs leverage the contextual understanding inherent in language to interpret visual data. This allows for more flexible and robust 3D scene understanding; a VLM can, for example, identify and locate an object described as “the red mug to the left of the keyboard” even with partial occlusion or varying lighting conditions. By grounding language in visual features, these models effectively bridge the semantic gap between human instruction and robotic perception, enabling more intuitive and adaptable 3D object localization and scene interpretation.
This research evaluates the efficacy of current Vision-Language Models (VLMs) in estimating 3D object positions. Specifically, we benchmarked LLaVA-v1.5, Mistral LLaVA-NeXT, and LLaVA-Onevision, selected for their established performance in vision-language tasks. Performance was measured by assessing the models’ ability to accurately determine the x, y, and z coordinates of objects within a given visual scene, based on textual prompts or queries. The evaluation methodology focuses on quantifying the error between the model’s predicted 3D positions and the ground truth data, providing a comparative analysis of each VLM’s spatial reasoning capabilities.
Data acquisition for model evaluation was conducted using a Doosan A0509 Robot Arm and a Logitech Brio Webcam to simulate a realistic robotic perception environment. The Doosan A0509, a six-axis industrial robot, provided controlled movements and viewpoints for capturing visual data. The Logitech Brio Webcam, selected for its high resolution and frame rate, served as the primary sensor for image capture. This hardware configuration enabled the collection of a dataset representative of the challenges encountered in robotic applications, specifically focusing on 3D object localization and perception tasks. Data was gathered under varying lighting conditions and object orientations to ensure robustness testing of the evaluated Vision-Language Models.
Parameter Efficiency and Computational Acceleration
Low-Rank Adaptation (LoRA) is implemented as a parameter-efficient fine-tuning technique for Visual Language Models (VLMs). Rather than updating all model parameters during training, LoRA introduces trainable low-rank decomposition matrices to the existing weights. This reduces the number of trainable parameters significantly, decreasing computational cost and memory requirements while maintaining performance. Specifically, LoRA approximates weight updates with a low-rank matrix factorization, allowing adaptation with a smaller parameter footprint compared to full fine-tuning. This approach facilitates faster experimentation and enables the effective adaptation of large VLMs on limited hardware resources.
Model training leverages the computational resources of NVIDIA Tesla A100 GPUs orchestrated via the Slurm Cluster workload manager. This distributed training infrastructure enables parallel processing of training data, significantly reducing the time required for experimentation and model convergence. The Slurm Cluster facilitates efficient resource allocation and job scheduling across multiple GPUs, allowing for scalable training runs and faster iteration on model architectures and hyperparameters. This approach is critical for handling the large datasets and complex models associated with visual language understanding tasks.
Model evaluation employs Huber Loss as the loss function, a combination of Mean Squared Error and Mean Absolute Error, to reduce sensitivity to outliers. Accuracy is quantified using Mean Absolute Error (MAE), reporting a median absolute error of 13mm for 3D object position estimation. Additionally, the Cumulative Distribution Function (CDF) is used to analyze the distribution of errors, providing a more comprehensive understanding of model performance beyond simple averages. The median Euclidean distance error, another metric for 3D position accuracy, is reported as 27mm.

From Validation to Dynamic Environments: Charting a Course for Intelligent Robotics
Rigorous testing of these visual language models (VLMs) involved integration with a Doosan A0509 Robot Arm, a platform chosen to simulate the complexities of real-world robotic environments. This setup allowed researchers to evaluate the system’s ability to accurately estimate the 3D position of objects amidst typical workspace clutter and varying lighting conditions. The results confirm the feasibility of deploying VLMs for robotic applications, demonstrating a capacity for reliable object localization crucial for tasks like pick-and-place operations, automated assembly, and dynamic environment mapping. This validation signifies a move towards more adaptable and intelligent robotic systems capable of operating effectively in unstructured settings.
A key innovation within this system lies in its Conditional Routing Mechanism, designed to intelligently distribute prompts between specialized, adapted models and a foundational base model. This dynamic allocation optimizes performance by leveraging the strengths of each model – the adapted versions excel at specific object categories, while the base model provides robust generalization. Evaluations demonstrate this approach significantly surpasses previous methods, achieving a five-fold improvement in accuracy. Notably, the system now successfully estimates object positions within a 10mm margin of error for 25% of tested samples, representing a substantial leap towards reliable 3D perception in complex robotic environments.
Continued development seeks to move beyond static estimation, integrating these visual localization models directly into the closed loop of real-time robotic control systems for dynamic environments. Researchers are particularly interested in leveraging the efficiency of Locally Encoded Radiance Fields (LERF) – a compact representation of 3D scenes – to accelerate processing and reduce computational demands on robotic platforms. This includes investigating compatibility with the RT-X family of processors and exploring advanced models like VFMM3D and MonoDETR, which offer promising capabilities in visual feature matching and monocular depth estimation, ultimately striving for more robust and efficient robotic perception and manipulation.
The presented research meticulously dissects the challenge of 3D object localization from monocular images, mirroring a core tenet of computational vision: extracting meaningful structure from raw sensory input. This process, akin to deciphering patterns within complex data, relies heavily on the interplay between visual perception and linguistic understanding, as embodied by the Vision-Language Models. As David Marr stated, “Vision is not about seeing what is there, but about constructing a representation of what is there.” This resonates with the study’s focus on building a robust, interpretable system capable of translating 2D images into a 3D understanding of the environment. If a pattern cannot be reproduced or explained, it doesn’t exist.
Beyond the Horizon
The presented work, while achieving promising results in monocular 3D object position estimation, highlights a persistent tension inherent in translating visual data into spatial understanding. A 13mm median absolute error, though seemingly precise, masks the inevitable accumulation of uncertainty when inferring depth from a single perspective. Future investigations must rigorously examine the characteristics of these errors – are they systematic biases related to object size, texture, or scene complexity? Or do they represent the fundamental limit of information obtainable from impoverished visual input?
The application of Vision-Language Models offers a novel, yet presently underexplored, avenue for incorporating contextual reasoning. However, the reliance on pre-trained models introduces an external dependency – the ‘knowledge’ embedded within these models may not generalize to all robotic interaction scenarios. A critical next step involves developing methods for adapting and refining these models with task-specific data, or exploring alternative approaches that prioritize efficient learning from limited examples.
Ultimately, the true measure of success lies not simply in minimizing error metrics, but in demonstrating robust performance in dynamic, real-world environments. Open-set detection represents a crucial component of this challenge, but it demands a more nuanced understanding of how to quantify and mitigate the risks associated with encountering unforeseen objects or situations. The cycle of observation, hypothesis, and experiment continues, perpetually revealing the limitations of current understanding and guiding the pursuit of more robust and adaptable systems.
Original article: https://arxiv.org/pdf/2603.01224.pdf
Contact the author: https://www.linkedin.com/in/avetisyan/
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2026-03-04 05:25