OpenDlign: Enhancing Open-World 3D Learning with Depth-Aligned Images

Recent advances in Vision and Language Models (VLMs) have improved open-world 3D representation, facilitating 3D zero-shot capability in unseen categories. Existing open-world methods pre-train an extra 3D encoder to align features from 3D data (e.g., depth maps or point clouds) with CAD-rendered images and corresponding texts. However, the limited color and texture variations in CAD images can compromise the alignment robustness. Furthermore, the volume discrepancy between pre-training datasets of the 3D encoder and VLM leads to sub-optimal 2D to 3D knowledge transfer. To overcome these issues, we propose OpenDlign, a novel framework for learning open-world 3D representations, that leverages depth-aligned images generated from point cloud-projected depth maps. Unlike CAD-rendered images, our generated images provide rich, realistic color and texture diversity while preserving geometric and semantic consistency with the depth maps. OpenDlign also optimizes depth map projection and integrates depth-specific text prompts, improving 2D VLM knowledge adaptation for 3D learning efficient fine-tuning. Experimental results show that OpenDlign significantly outperforms existing benchmarks in zero-shot and few-shot 3D tasks, exceeding prior scores by 8.0% on ModelNet40 and 16.4% on OmniObject3D with just 6 million tuned parameters. Moreover, integrating generated depth-aligned images into existing 3D learning pipelines consistently improves their performance.