CVPR 2024 Papers

Recent works have shown that generative models leave traces of their underlying generative process on the generated samples broadly referred to as fingerprints of a generative model and have studied their utility in detecting synthetic images from real ones. However the extend to which these fingerprints can distinguish between various types of synthetic image and help identify the underlying generative process remain under-explored. In particular the very definition of a fingerprint remains unclear to our knowledge. To that end in this work we formalize the definition of artifact and fingerprint in generative models propose an algorithm for computing them in practice and finally study its effectiveness in distinguishing a large array of different generative models. We find that using our proposed definition can significantly improve the performance on the task of identifying the underlying generative process from samples (model attribution) compared to existing methods. Additionally we study the structure of the fingerprints and observe that it is very predictive of the effect of different design choices on the generative process.

The task of online mapping is to predict a local map using current sensor observations e.g. from lidar and camera without relying on a pre-built map. State-of-the-art methods are based on supervised learning and are trained predominantly using two datasets: nuScenes and Argoverse 2. However these datasets revisit the same geographic locations across training validation and test sets. Specifically over 80% of nuScenes and 40% of Argoverse 2 validation and test samples are less than 5 m from a training sample. At test time the methods are thus evaluated more on how well they localize within a memorized implicit map built from the training data than on extrapolating to unseen locations. Naturally this data leakage causes inflated performance numbers and we propose geographically disjoint data splits to reveal the true performance in unseen environments. Experimental results show that methods perform considerably worse some dropping more than 45 mAP when trained and evaluated on proper data splits. Additionally a reassessment of prior design choices reveals diverging conclusions from those based on the original split. Notably the impact of lifting methods and the support from auxiliary tasks (e.g. depth supervision) on performance appears less substantial or follows a different trajectory than previously perceived.

Federated learning is a decentralized learning paradigm introduced to preserve privacy of client data. Despite this prior work has shown that an attacker at the server can still reconstruct the private training data using only the client updates. These attacks are known as data reconstruction attacks and fall into two major categories: gradient inversion (GI) and linear layer leakage attacks (LLL). However despite demonstrating the effectiveness of these attacks in breaching privacy prior work has not investigated the usefulness of the reconstructed data for downstream tasks. In this work we explore data reconstruction attacks through the lens of training and improving models with leaked data. We demonstrate the effectiveness of both GI and LLL attacks in maliciously training models using the leaked data more accurately than a benign federated learning strategy. Counter-intuitively this bump in training quality can occur despite limited reconstruction quality or a small total number of leaked images. Finally we show the limitations of these attacks for downstream training individually for GI attacks and for LLL attacks.

Human-object contact serves as a strong cue to understand how humans physically interact with objects. Nevertheless it is not widely explored to utilize human-object contact information for the joint reconstruction of 3D human and object from a single image. In this work we present a novel joint 3D human-object reconstruction method (CONTHO) that effectively exploits contact information between humans and objects. There are two core designs in our system: 1) 3D-guided contact estimation and 2) contact-based 3D human and object refinement. First for accurate human-object contact estimation CONTHO initially reconstructs 3D humans and objects and utilizes them as explicit 3D guidance for contact estimation. Second to refine the initial reconstructions of 3D human and object we propose a novel contact-based refinement Transformer that effectively aggregates human features and object features based on the estimated human-object contact. The proposed contact-based refinement prevents the learning of erroneous correlation between human and object which enables accurate 3D reconstruction. As a result our CONTHO achieves state-of-the-art performance in both human-object contact estimation and joint reconstruction of 3D human and object. The codes are available in https://github.com/dqj5182/CONTHO_RELEASE.

Understanding human social behaviour is crucial in computer vision and robotics. Micro-level observations like individual actions fall short necessitating a comprehensive approach that considers individual behaviour intra-group dynamics and social group levels for a thorough understanding. To address dataset limitations this paper introduces JRDB-Social an extension of JRDB. Designed to fill gaps in human understanding across diverse indoor and outdoor social contexts JRDB-Social provides annotations at three levels: individual attributes intra-group interactions and social group context. This dataset aims to enhance our grasp of human social dynamics for robotic applications. Utilizing the recent cutting-edge multi-modal large language models we evaluated our benchmark to explore their capacity to decipher social human behaviour.

Inverse rendering aims at recovering both geometry and materials of objects. It provides a more compatible reconstruction for conventional rendering engines compared with the neural radiance fields (NeRFs). On the other hand existing NeRF-based inverse rendering methods cannot handle glossy objects with local light interactions well as they typically oversimplify the illumination as a 2D environmental map which assumes infinite lights only. Observing the superiority of NeRFs in recovering radiance fields we propose a novel 5D Neural Plenoptic Function (NeP) based on NeRFs and ray tracing such that more accurate lighting-object interactions can be formulated via the rendering equation. We also design a material-aware cone sampling strategy to efficiently integrate lights inside the BRDF lobes with the help of pre-filtered radiance fields. Our method has two stages: the geometry of the target object and the pre-filtered environmental radiance fields are reconstructed in the first stage and materials of the target object are estimated in the second stage with the proposed NeP and material-aware cone sampling strategy. Extensive experiments on the proposed real-world and synthetic datasets demonstrate that our method can reconstruct high-fidelity geometry/materials of challenging glossy objects with complex lighting interactions from nearby objects. Project webpage: https://whyy.site/paper/nep

Quantifying the degree of similarity between images is a key copyright issue for image-based machine learning. In legal doctrine however determining the degree of similarity between works requires subjective analysis and fact-finders (judges and juries) can demonstrate considerable variability in these subjective judgement calls. Images that are structurally similar can be deemed dissimilar whereas images of completely different scenes can be deemed similar enough to support a claim of copying. We seek to define and compute a notion of "conceptual similarity" among images that captures high-level relations even among images that do not share repeated elements or visually similar components. The idea is to use a base multi-modal model to generate "explanations" (captions) of visual data at increasing levels of complexity. Then similarity can be measured by the length of the caption needed to discriminate between the two images: Two highly dissimilar images can be discriminated early in their description whereas conceptually dissimilar ones will need more detail to be distinguished. We operationalize this definition and show that it correlates with subjective (averaged human evaluation) assessment and beats existing baselines on both image-to-image and text-to-text similarity benchmarks. Beyond just providing a number our method also offers interpretability by pointing to the specific level of granularity of the description where the source data is differentiated.

Recently infrared small target detection (IRSTD) has been dominated by deep-learning-based methods. However these methods mainly focus on the design of complex model structures to extract discriminative features leaving the loss functions for IRSTD under-explored. For example the widely used Intersection over Union (IoU) and Dice losses lack sensitivity to the scales and locations of targets limiting the detection performance of detectors. In this paper we focus on boosting detection performance with a more effective loss but a simpler model structure. Specifically we first propose a novel Scale and Location Sensitive (SLS) loss to handle the limitations of existing losses: 1) for scale sensitivity we compute a weight for the IoU loss based on target scales to help the detector distinguish targets with different scales: 2) for location sensitivity we introduce a penalty term based on the center points of targets to help the detector localize targets more precisely. Then we design a simple Multi-Scale Head to the plain U-Net (MSHNet). By applying SLS loss to each scale of the predictions our MSHNet outperforms existing state-of-the-art methods by a large margin. In addition the detection performance of existing detectors can be further improved when trained with our SLS loss demonstrating the effectiveness and generalization of our SLS loss. The code is available at https://github.com/ying-fu/MSHNet.

Neural Radiance Fields (NeRF) exhibit remarkable performance for Novel View Synthesis (NVS) given a set of 2D images. However NeRF training requires accurate camera pose for each input view typically obtained by Structure-from-Motion (SfM) pipelines. Recent works have attempted to relax this constraint but they still often rely on decent initial poses which they can refine. Here we aim at removing the requirement for pose initialization. We present Incremental CONfidence (ICON) an optimization procedure for training NeRFs from 2D video frames. ICON only assumes smooth camera motion to estimate initial guess for poses. Further ICON introduces "confidence": an adaptive measure of model quality used to dynamically reweight gradients. ICON relies on high-confidence poses to learn NeRF and high-confidence 3D structure (as encoded by NeRF) to learn poses. We show that ICON without prior pose initialization achieves superior performance in both CO3D and HO3D versus methods which use SfM pose.

Mesh denoising (MD) is a critical task in geometry processing as meshes from scanning or AIGC techniques are susceptible to noise contamination. The challenge of MD lies in the diverse nature of mesh facets in terms of geometric characteristics and noise distributions. Despite recent advancements in deep learning-based MD methods existing MD networks typically neglect the consideration of geometric characteristics and noise distributions. In this paper we propose Hyper-MD a hyper-network-based approach that addresses this limitation by dynamically customizing denoising parameters for each facet based on its noise intensity and geometric characteristics. Specifically Hyper-MD is composed of a hyper-network and an MD network. For each noisy facet the hyper-network takes two angles as input to customize parameters for the MD network. These two angles are specially defined to reveal the noise intensity and geometric characteristics of the current facet respectively. The MD network receives a facet patch as input and outputs the denoised normal using the customized parameters. Experimental results on synthetic and real-scanned meshes demonstrate that Hyper-MD outperforms state-of-the-art mesh denoising methods.

Adversarial attack methods based on point manipulation for 3D point cloud classification have revealed the fragility of 3D models yet the adversarial examples they produce are easily perceived or defended against. The trade-off between the imperceptibility and adversarial strength leads most point attack methods to inevitably introduce easily detectable outlier points upon a successful attack. Another promising strategy shape-based attack can effectively eliminate outliers but existing methods often suffer significant reductions in imperceptibility due to irrational deformations. We find that concealing deformation perturbations in areas insensitive to human eyes can achieve a better trade-off between imperceptibility and adversarial strength specifically in parts of the object surface that are complex and exhibit drastic curvature changes. Therefore we propose a novel shape-based adversarial attack method HiT-ADV which initially conducts a two-stage search for attack regions based on saliency and imperceptibility scores and then adds deformation perturbations in each attack region using Gaussian kernel functions. Additionally HiT-ADV is extendable to physical attack. We propose that by employing benign resampling and benign rigid transformations we can further enhance physical adversarial strength with little sacrifice to imperceptibility. Extensive experiments have validated the superiority of our method in terms of adversarial and imperceptible properties in both digital and physical spaces.

Recent progress in single-image 3D generation highlights the importance of multi-view coherency leveraging 3D priors from large-scale diffusion models pretrained on Internet-scale images. However the aspect of novel-view diversity remains underexplored within the research landscape due to the ambiguity in converting a 2D image into 3D content where numerous potential shapes can emerge. Here we aim to address this research gap by simultaneously addressing both consistency and diversity. Yet striking a balance between these two aspects poses a considerable challenge due to their inherent trade-offs. This work introduces HarmonyView a simple yet effective diffusion sampling technique adept at decomposing two intricate aspects in single-image 3D generation: consistency and diversity. This approach paves the way for a more nuanced exploration of the two critical dimensions within the sampling process. Moreover we propose a new evaluation metric based on CLIP image and text encoders to comprehensively assess the diversity of the generated views which closely aligns with human evaluators' judgments. In experiments HarmonyView achieves a harmonious balance demonstrating a win-win scenario in both consistency and diversity.

Humans naturally interact with both others and the surrounding multiple objects engaging in various social activities. However recent advances in modeling human-object interactions mostly focus on perceiving isolated individuals and objects due to fundamental data scarcity. In this paper we introduce HOI-M^3 a novel large-scale dataset for modeling the interactions of Multiple huMans and Multiple objects. Notably it provides accurate 3D tracking for both humans and objects from dense RGB and object-mounted IMU inputs covering 199 sequences and 181M frames of diverse humans and objects under rich activities. With the unique HOI-M^3 dataset we introduce two novel data-driven tasks with companion strong baselines: monocular capture and unstructured generation of multiple human-object interactions. Extensive experiments demonstrate that our dataset is challenging and worthy of further research about multiple human-object interactions and behavior analysis. Our HOI-M^3 dataset corresponding codes and pre-trained models will be disseminated to the community for future research.

Social interaction is a fundamental aspect of human behavior and communication. The way individuals position themselves in relation to others also known as proxemics conveys social cues and affects the dynamics of social interaction. Reconstructing such interaction from images presents challenges because of mutual occlusion and the limited availability of large training datasets. To address this we present a novel approach that learns a prior over the 3D proxemics two people in close social interaction and demonstrate its use for single-view 3D reconstruction. We start by creating 3D training data of interacting people using image datasets with contact annotations. We then model the proxemics using a novel denoising diffusion model called BUDDI that learns the joint distribution over the poses of two people in close social interaction. Sampling from our generative proxemics model produces realistic 3D human interactions which we validate through a perceptual study. We use BUDDI in reconstructing two people in close proximity from an image without any contact annotation via an optimization approach that uses the diffusion model as a prior. Our approach recovers accurate 3D social interactions from noisy initial estimates outperforming state-of-the-art methods. Our code data and model are available at: muelea.github.io/buddi.

The lightweight "local-match-global" matching introduced by SRe2L successfully creates a distilled dataset with comprehensive information on the full 224x224 ImageNet-1k. However this one-sided approach is limited to a particular backbone layer and statistics which limits the improvement of the generalization of a distilled dataset. We suggest that sufficient and various "local-match-global" matching are more precise and effective than a single one and has the ability to create a distilled dataset with richer information and better generalization. We call this perspective "generalized matching" and propose Generalized Various Backbone and Statistical Matching (G-VBSM) in this work which aims to create a synthetic dataset with densities ensuring consistency with the complete dataset across various backbones layers and statistics. As experimentally demonstrated G-VBSM is the first algorithm to obtain strong performance across both small-scale and large-scale datasets. Specifically G-VBSM achieves a performance of 38.7% on CIFAR-100 with 128-width ConvNet 47.6% on Tiny-ImageNet with ResNet18 and 31.4% on the full 224x224 ImageNet-1k with ResNet18 under images per class (IPC) 10 50 and 10 respectively. These results surpass all SOTA methods by margins of 3.9% 6.5% and 10.1% respectively.

The pre-training architectures of large language models encompass various types including autoencoding models autoregressive models and encoder-decoder models. We posit that any modality can potentially benefit from a large language model as long as it undergoes vector quantization to become discrete tokens. Inspired by the General Language Model we propose a General Point Model (GPM) that seamlessly integrates autoencoding and autoregressive tasks in a point cloud transformer. This model is versatile allowing fine-tuning for downstream point cloud representation tasks as well as unconditional and conditional generation tasks. GPM enhances masked prediction in autoencoding through various forms of mask padding tasks leading to improved performance in point cloud understanding. Additionally GPM demonstrates highly competitive results in unconditional point cloud generation tasks even exhibiting the potential for conditional generation tasks by modifying the input's conditional information. Compared to models like Point-BERT MaskPoint and PointMAE our GPM achieves superior performance in point cloud understanding tasks. Furthermore the integration of autoregressive and autoencoding within the same transformer underscores its versatility across different downstream tasks.

We introduce Gaussian Articulated Template Model (GART) an explicit efficient and expressive representation for non-rigid articulated subject capturing and rendering from monocular videos. GART utilizes a mixture of moving 3D Gaussians to explicitly approximate a deformable subject's geometry and appearance. It takes advantage of a categorical template model prior (SMPL SMAL etc.) with learnable forward skinning while further generalizing to more complex non-rigid deformations with novel latent bones. GART can be reconstructed via differentiable rendering from monocular videos in seconds or minutes and rendered in novel poses faster than 150fps.