DPA: Dual Prototypes Alignment for Unsupervised Adaptation of Vision-Language Models

Vision-language models (VLMs), e.g., CLIP, have shown remarkable potential in zero-shot image classification. However, adapting these models to new domains remains challenging, especially in unsupervised settings where labelled data is unavailable. Recent research has proposed pseudo-labelling approaches to adapt CLIP in an unsupervised manner using unlabelled target data. Nonetheless, these methods struggle due to noisy pseudo-labels resulting from the misalignment between CLIP's visual and textual representations. This study introduces DPA, an unsupervised domain adaptation method for VLMs. DPA introduces the concept of dual prototypes, acting as distinct classifiers, along with the convex combination of their outputs, thereby leading to accurate pseudo-label construction. Next, it ranks pseudo-labels to facilitate robust self-training, particularly during early training. Finally, it addresses visual-textual misalignment by aligning textual prototypes with image prototypes to further improve the adaptation performance. Experiments on 13 downstream vision tasks demonstrate that DPA significantly outperforms zero-shot CLIP and the state-of-the-art unsupervised adaptation baselines.

S2TPVFormer: Spatio-Temporal Tri-Perspective View for temporally coherent 3D Semantic Occupancy Prediction

Holistic understanding and reasoning in 3D scenes play a vital role in the success of autonomous driving systems. The evolution of 3D semantic occupancy prediction as a pretraining task for autonomous driving and robotic downstream tasks captures finer 3D details compared to methods like 3D detection. Existing approaches predominantly focus on spatial cues, often overlooking temporal cues. Query-based methods tend to converge on computationally intensive Voxel representation for encoding 3D scene information. This study introduces S2TPVFormer, an extension of TPVFormer, utilizing a spatiotemporal transformer architecture for coherent 3D semantic occupancy prediction. Emphasizing the importance of spatiotemporal cues in 3D scene perception, particularly in 3D semantic occupancy prediction, our work explores the less-explored realm of temporal cues. Leveraging Tri-Perspective View (TPV) representation, our spatiotemporal encoder generates temporally rich embeddings, improving prediction coherence while maintaining computational efficiency. To achieve this, we propose a novel Temporal Cross-View Hybrid Attention (TCVHA) mechanism, facilitating effective spatiotemporal information exchange across TPV views. Experimental evaluations on the nuScenes dataset demonstrate a substantial 3.1% improvement in mean Intersection over Union (mIoU) for 3D Semantic Occupancy compared to TPVFormer, confirming the effectiveness of the proposed S2TPVFormer in enhancing 3D scene perception.