CVPR 2024 Papers

Precipitation nowcasting is an important spatio-temporal prediction task to predict the radar echoes sequences based on current observations which can serve both meteorological science and smart city applications. Due to the chaotic evolution nature of the precipitation systems it is a very challenging problem. Previous studies address the problem either from the perspectives of deterministic modeling or probabilistic modeling. However their predictions suffer from the blurry high-value echoes fading away and position inaccurate issues. The root reason of these issues is that the chaotic evolutionary precipitation systems are not appropriately modeled. Inspired by the nature of the systems we propose to decompose and model them from the perspective of global deterministic motion and local stochastic variations with residual mechanism. A unified and flexible framework that can equip any type of spatio-temporal models is proposed based on residual diffusion which effectively tackles the shortcomings of previous methods. Extensive experimental results on four publicly available radar datasets demonstrate the effectiveness and superiority of the proposed framework compared to state-of-the-art techniques. Our code is publicly available at https://github.com/DeminYu98/DiffCast.

In image question answering due to the abundant and sometimes redundant information precisely matching and integrating the information from both text and images is a challenge. In this paper we propose the Decomposition-Integration Enhancing Multimodal Insight (DIEM) which initially decomposes the given question and image into multiple subquestions and several sub-images aiming to isolate specific elements for more focused analysis. We then integrate these sub-elements by matching each subquestion with its relevant sub-images while also retaining the original image to construct a comprehensive answer to the original question without losing sight of the overall context. This strategy mirrors the human cognitive process of simplifying complex problems into smaller components for individual analysis followed by an integration of these insights. We implement DIEM on the LLaVA-v1.5 model and evaluate its performance on ScienceQA and MM-Vet. Experimental results indicate that our method boosts accuracy in most question classes of the ScienceQA (+2.03% in average) especially in the image modality (+3.40%). On MM-Vet our method achieves an improvement in MM-Vet scores increasing from 31.1 to 32.4. These findings highlight DIEM's effectiveness in harmonizing the complexities of multimodal data demonstrating its ability to enhance accuracy and depth in image question answering through its decomposition-integration process.

Existing super-resolution (SR) models primarily focus on restoring local texture details often neglecting the global semantic information within the scene. This oversight can lead to the omission of crucial semantic details or the introduction of inaccurate textures during the recovery process. In our work we introduce the Cognitive Super-Resolution (CoSeR) framework empowering SR models with the capacity to comprehend low-resolution images. We achieve this by marrying image appearance and language understanding to generate a cognitive embedding which not only activates prior information from large text-to-image diffusion models but also facilitates the generation of high-quality reference images to optimize the SR process. To further improve image fidelity we propose a novel condition injection scheme called "All-in-Attention" consolidating all conditional information into a single module. Consequently our method successfully restores semantically correct and photorealistic details demonstrating state-of-the-art performance across multiple benchmarks. Project page: https://coser-main.github.io/

Stable Diffusion has established itself as a foundation model in generative AI artistic applications receiving widespread research and application. Some recent fine-tuning methods have made it feasible for individuals to implant personalized concepts onto the basic Stable Diffusion model with minimal computational costs on small datasets. However these innovations have also given rise to issues like facial privacy forgery and artistic copyright infringement. In recent studies researchers have explored the addition of imperceptible adversarial perturbations to images to prevent potential unauthorized exploitation and infringements when personal data is used for fine-tuning Stable Diffusion. Although these studies have demonstrated the ability to protect images it is essential to consider that these methods may not be entirely applicable in real-world scenarios. In this paper we systematically evaluate the use of perturbations to protect images within a practical threat model. The results suggest that these approaches may not be sufficient to safeguard image privacy and copyright effectively. Furthermore we introduce a purification method capable of removing protected perturbations while preserving the original image structure to the greatest extent possible. Experiments reveal that Stable Diffusion can effectively learn from purified images over all protective methods.

Accurately predicting the 3D human posture and the pressure exerted on the body for people resting in bed visualized as a body mesh (3D pose & shape) with a 3D pressure map holds significant promise for healthcare applications particularly in the prevention of pressure ulcers. Current methods focus on singular facets of the problem---predicting only 2D/3D poses generating 2D pressure images predicting pressure only for certain body regions instead of the full body or forming indirect approximations to the 3D pressure map. In contrast we introduce BodyMAP which jointly predicts the human body mesh and 3D applied pressure map across the entire human body. Our network leverages multiple visual modalities incorporating both a depth image of a person in bed and its corresponding 2D pressure image acquired from a pressure-sensing mattress. The 3D pressure map is represented as a pressure value at each mesh vertex and thus allows for precise localization of high-pressure regions on the body. Additionally we present BodyMAP-WS a new formulation of pressure prediction in which we implicitly learn pressure in 3D by aligning sensed 2D pressure images with a differentiable 2D projection of the predicted 3D pressure maps. In evaluations with real-world human data our method outperforms the current state-of-the-art technique by 25% on both body mesh and 3D applied pressure map prediction tasks for people in bed.

Data mixing methods play a crucial role in semi-supervised learning (SSL) but their application is unexplored in long-tailed semi-supervised learning (LTSSL). The primary reason is that the in-batch mixing manner fails to address class imbalance. Furthermore existing LTSSL methods mainly focus on re-balancing data quantity but ignore class-wise uncertainty which is also vital for class balance. For instance some classes with sufficient samples might still exhibit high uncertainty due to indistinguishable features. To this end this paper introduces the Balanced and Entropy-based Mix (BEM) a pioneering mixing approach to re-balance the class distribution of both data quantity and uncertainty. Specifically we first propose a class balanced mix bank to store data of each class for mixing. This bank samples data based on the estimated quantity distribution thus re-balancing data quantity. Then we present an entropy-based learning approach to re-balance class-wise uncertainty including entropy-based sampling strategy entropy-based selection module and entropy-based class balanced loss. Our BEM first leverages data mixing for improving LTSSL and it can also serve as a complement to the existing re-balancing methods. Experimental results show that BEM significantly enhances various LTSSL frameworks and achieves state-of-the-art performances across multiple benchmarks.

We present the subspace-constrained Tyler's estimator (STE) designed for recovering a low-dimensional subspace within a dataset that may be highly corrupted with outliers. STE is a fusion of the Tyler's M-estimator (TME) and a variant of the fast median subspace. Our theoretical analysis suggests that under a common inlier-outlier model STE can effectively recover the underlying subspace even when it contains a smaller fraction of inliers relative to other methods in the field of robust subspace recovery. We apply STE in the context of Structure from Motion (SfM) in two ways: for robust estimation of the fundamental matrix and for the removal of outlying cameras enhancing the robustness of the SfM pipeline. Numerical experiments confirm the state-of-the-art performance of our method in these applications. This research makes significant contributions to the field of robust subspace recovery particularly in the context of computer vision and 3D reconstruction.

Visual content creation has aroused a surge of interest given its applications in mobile photography and AR/VR. Portrait style transfer and 3D recovery from monocular images as two representative tasks have so far evolved independently. In this paper we make a connection between the two and tackle the challenging task of 3D portrait stylization - modeling high-fidelity 3D stylized avatars from captured 2D portrait images. However naively combining the techniques from the two isolated areas may suffer from either inadequate stylization or absence of 3D assets. To this end we propose 3DToonify a new framework that introduces a progressive training scheme to achieve 3D style adaption on spatial neural representation (SNR). SNR is constructed with implicit fields and they are dynamically optimized by the progressive training scheme which consists of three stages: guided prior learning deformable geometry adaption and explicit texture adaption. In this way stylized geometry and texture are learned in SNR in an explicit and structured way with only a single stylized exemplar needed. Moreover our method obtains style-adaptive underlying structures (i.e. deformable geometry and exaggerated texture) and view-consistent stylized avatar rendering from arbitrary novel viewpoints. Both qualitative and quantitative experiments have been conducted to demonstrate the effectiveness and superiority of our method for automatically generating exemplar-guided 3D stylized avatars.