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Meng-Li Shih, Wei-Chiu Ma, Lorenzo Boyice, Aleksander Holynski, Forrester Cole, Brian Curless, Janne Kontkanen

We propose ExtraNeRF a novel method for extrapolating the range of views handled by a Neural Radiance Field (NeRF). Our main idea is to leverage NeRFs to model scene-specific fine-grained details while capitalizing on diffusion models to extrapolate beyond our observed data. A key ingredient is to track visibility to determine what portions of the scene have not been observed and focus on reconstructing those regions consistently with diffusion models. Our primary contributions include a visibility-aware diffusion-based inpainting module that is fine-tuned on the input imagery yielding an initial NeRF with moderate quality (often blurry) inpainted regions followed by a second diffusion model trained on the input imagery to consistently enhance notably sharpen the inpainted imagery from the first pass. We demonstrate high-quality results extrapolating beyond a small number of (typically six or fewer) input views effectively outpainting the NeRF as well as inpainting newly disoccluded regions inside the original viewing volume. We compare with related work both quantitatively and qualitatively and show significant gains over prior art.

Tianyu Huang, Liangzu Peng, Rene Vidal, Yun-Hui Liu

Given an input set of 3D point pairs the goal of outlier-robust 3D registration is to compute some rotation and translation that align as many point pairs as possible. This is an important problem in computer vision for which many highly accurate approaches have been recently proposed. Despite their impressive performance these approaches lack scalability often overflowing the 16GB of memory of a standard laptop to handle roughly 30000 point pairs. In this paper we propose a 3D registration approach that can process more than ten million (10^7) point pairs with over 99% random outliers. Moreover our method is efficient entails low memory costs and maintains high accuracy at the same time. We call our method TEAR as it involves minimizing an outlier-robust loss that computes Truncated Entry-wise Absolute Residuals. To minimize this loss we decompose the original 6-dimensional problem into two subproblems of dimensions 3 and 2 respectively solved in succession to global optimality via a customized branch-and-bound method. While branch-and-bound is often slow and unscalable this does not apply to TEAR as we propose novel bounding functions that are tight and computationally efficient. Experiments on various datasets are conducted to validate the scalability and efficiency of our method.

Gabriele Trivigno, Carlo Masone, Barbara Caputo, Torsten Sattler

Pose refinement is an interesting and practically relevant research direction. Pose refinement can be used to (1) obtain a more accurate pose estimate from an initial prior (e.g. from retrieval) (2) as pre-processing i.e. to provide a better starting point to a more expensive pose estimator (3) as post-processing of a more accurate localizer. Existing approaches focus on learning features / scene representations for the pose refinement task. This involves training an implicit scene representation or learning features while optimizing a camera pose-based loss. A natural question is whether training specific features / representations is truly necessary or whether similar results can be already achieved with more generic features. In this work we present a simple approach that combines pre-trained features with a particle filter and a renderable representation of the scene. Despite its simplicity it achieves state-of-the-art results demonstrating that one can easily build a pose refiner without the need for specific training. The code will be released upon acceptance.

Hao Jiang, Bingfeng Zhou, Yadong Mu

Halftoning is a time-honored printing technique that simulates continuous tones using ink dots (halftone dots). The resurgence of deep learning has catalyzed the emergence of innovative technologies in the printing industry fostering the advancement of data-driven halftoning methods. Nevertheless current deep learning-based approaches produce halftones through image-to-image black box transformations lacking direct control over the movement of individual halftone dots. In this paper we propose an innovative halftoning method termed "neural dot-controllable halftoning". This method allows dot-level image dithering by providing direct control over the motion of each ink dot. We conceptualize halftoning as the process of sprinkling dots on a canvas. Initially a specific quantity of dots are randomly dispersed on the canvas and subsequently adjusted based on the surrounding grayscale and gradient. To establish differentiable transformations between discrete ink dot positions and halftone matrices we devise a lightweight dot encoding network to spread dense gradients to sparse dots. Dot control offers several advantages to our approach including the capability to regulate the quantity of halftone dots and enhance specific areas with artifacts in the generated halftones by adjusting the placement of the dots. Our proposed method exhibits superior performance than previous approaches in extensive quantitative and qualitative experiments.

Guangyu Wang, Jinzhi Zhang, Fan Wang, Ruqi Huang, Lu Fang

We propose XScale-NVS for high-fidelity cross-scale novel view synthesis of real-world large-scale scenes. Existing representations based on explicit surface suffer from discretization resolution or UV distortion while implicit volumetric representations lack scalability for large scenes due to the dispersed weight distribution and surface ambiguity. In light of the above challenges we introduce hash featurized manifold a novel hash-based featurization coupled with a deferred neural rendering framework. This approach fully unlocks the expressivity of the representation by explicitly concentrating the hash entries on the 2D manifold thus effectively representing highly detailed contents independent of the discretization resolution. We also introduce a novel dataset namely GigaNVS to benchmark cross-scale high-resolution novel view synthesis of real-world large-scale scenes. Our method significantly outperforms competing baselines on various real-world scenes yielding an average LPIPS that is ?40% lower than prior state-of-the-art on the challenging GigaNVS benchmark. Please see our project page at: xscalenvs.github.io.

Aysim Toker, Marvin Eisenberger, Daniel Cremers, Laura Leal-Taixé

In recent years semantic segmentation has become a pivotal tool in processing and interpreting satellite imagery. Yet a prevalent limitation of supervised learning techniques remains the need for extensive manual annotations by experts. In this work we explore the potential of generative image diffusion to address the scarcity of annotated data in earth observation tasks. The main idea is to learn the joint data manifold of images and labels leveraging recent advancements in denoising diffusion probabilistic models. To the best of our knowledge we are the first to generate both images and corresponding masks for satellite segmentation. We find that the obtained pairs not only display high quality in fine-scale features but also ensure a wide sampling diversity. Both aspects are crucial for earth observation data where semantic classes can vary severely in scale and occurrence frequency. We employ the novel data instances for downstream segmentation as a form of data augmentation. In our experiments we provide comparisons to prior works based on discriminative diffusion models or GANs. We demonstrate that integrating generated samples yields significant quantitative improvements for satellite semantic segmentation -- both compared to baselines and when training only on the original data.

Lei Fan, Mingfu Liang, Yunxuan Li, Gang Hua, Ying Wu

Active recognition enables robots to intelligently explore novel observations thereby acquiring more information while circumventing undesired viewing conditions. Recent approaches favor learning policies from simulated or collected data wherein appropriate actions are more frequently selected when the recognition is accurate. However most recognition modules are developed under the closed-world assumption which makes them ill-equipped to handle unexpected inputs such as the absence of the target object in the current observation. To address this issue we propose treating active recognition as a sequential evidence-gathering process providing by-step uncertainty quantification and reliable prediction under the evidence combination theory. Additionally the reward function developed in this paper effectively characterizes the merit of actions when operating in open-world environments. To evaluate the performance we collect a dataset from an indoor simulator encompassing various recognition challenges such as distance occlusion levels and visibility. Through a series of experiments on recognition and robustness analysis we demonstrate the necessity of introducing uncertainties to active recognition and the superior performance of the proposed method.

Yake Wei, Ruoxuan Feng, Zihe Wang, Di Hu

One primary topic of multimodal learning is to jointly incorporate heterogeneous information from different modalities. However most models often suffer from unsatisfactory multimodal cooperation which cannot jointly utilize all modalities well. Some methods are proposed to identify and enhance the worse learnt modality but they are often hard to provide the fine-grained observation of multimodal cooperation at sample-level with theoretical support. Hence it is essential to reasonably observe and improve the fine-grained cooperation between modalities especially when facing realistic scenarios where the modality discrepancy could vary across different samples. To this end we introduce a sample-level modality valuation metric to evaluate the contribution of each modality for each sample. Via modality valuation we observe that modality discrepancy indeed could be different at sample-level beyond the global contribution discrepancy at dataset-level. We further analyze this issue and improve cooperation between modalities at sample-level by enhancing the discriminative ability of low-contributing modalities in a targeted manner. Overall our methods reasonably observe the fine-grained uni-modal contribution and achieve considerable improvement. The source code and dataset are available at https://github.com/GeWu-Lab/Valuate-and-Enhance-Multimodal-Cooperation.

Minghui Hu, Jianbin Zheng, Chuanxia Zheng, Chaoyue Wang, Dacheng Tao, Tat-Jen Cham

It is well known that many open-released foundational diffusion models have difficulty in generating images that substantially depart from average brightness despite such images being present in the training data. This is due to an inconsistency: while denoising starts from pure Gaussian noise during inference the training noise schedule retains residual data even in the final timestep distribution due to difficulties in numerical conditioning in mainstream formulation leading to unintended bias during inference. To mitigate this issue certain eps-prediction models are combined with an ad-hoc offset-noise methodology. In parallel some contemporary models have adopted zero-terminal SNR noise schedules together with v-prediction which necessitate major alterations to pre-trained models. However such changes risk destabilizing a large multitude of community-driven applications anchored on these pre-trained models. In light of this our investigation revisits the fundamental causes leading to our proposal of an innovative and principled remedy called One More Step (OMS). By integrating a compact network and incorporating an additional simple yet effective step during inference OMS elevates image fidelity and harmonizes the dichotomy between training and inference while preserving original model parameters. Once trained various pre-trained diffusion models with the same latent domain can share the same OMS module.

Siteng Huang, Biao Gong, Yutong Feng, Min Zhang, Yiliang Lv, Donglin Wang

Recent compositional zero-shot learning (CZSL) methods adapt pre-trained vision-language models (VLMs) by constructing trainable prompts only for composed state-object pairs. Relying on learning the joint representation of seen compositions these methods ignore the explicit modeling of the state and object thus limiting the exploitation of pre-trained knowledge and generalization to unseen compositions. With a particular focus on the universality of the solution in this work we propose a novel paradigm for CZSL models that establishes three identification branches (i.e. Multi-Path) to jointly model the state object and composition. The presented Troika is an outstanding implementation that aligns the branch-specific prompt representations with decomposed visual features. To calibrate the bias between semantically similar multi-modal representations we further devise a Cross-Modal Traction module into Troika that shifts the prompt representation towards the current visual content. We conduct extensive experiments on three popular benchmarks where our method significantly outperforms existing methods in both closed-world and open-world settings. The code will be available at https://github.com/bighuang624/Troika.

Paul Roetzer, Florian Bernard

Finding shortest paths on product spaces is a popular approach to tackle numerous variants of matching problems including the dynamic time warping method for matching signals the matching of curves or the matching of a curve to a 3D shape. While these approaches admit the computation of globally optimal solutions in polynomial time their natural generalisation to 3D shape matching is widely known to be intractable. In this work we address this issue by proposing a novel path-based formalism for 3D shape matching. More specifically we consider an alternative shape discretisation in which one of the 3D shapes (the source shape) is represented as a SpiderCurve i.e. a long self-intersecting curve that traces the 3D shape surface. We then tackle the 3D shape matching problem as finding a shortest path in the product graph of the SpiderCurve and the target 3D shape. Our approach introduces a set of novel constraints that ensure a globally geometrically consistent matching. Overall our formalism leads to an integer linear programming problem for which we experimentally show that it can efficiently be solved to global optimality. We demonstrate that our approach is competitive with recent state-of-the-art shape matching methods while in addition guaranteeing geometric consistency.

Shuofeng Sun, Yongming Rao, Jiwen Lu, Haibin Yan

Numerous prior studies predominantly emphasize constructing relation vectors for individual neighborhood points and generating dynamic kernels for each vector and embedding these into high-dimensional spaces to capture implicit local structures. However we contend that such implicit high-dimensional structure modeling approch inadequately represents the local geometric structure of point clouds due to the absence of explicit structural information. Hence we introduce X-3D an explicit 3D structure modeling approach. X-3D functions by capturing the explicit local structural information within the input 3D space and employing it to produce dynamic kernels with shared weights for all neighborhood points within the current local region. This modeling approach introduces effective geometric prior and significantly diminishes the disparity between the local structure of the embedding space and the original input point cloud thereby improving the extraction of local features. Experiments show that our method can be used on a variety of methods and achieves state-of-the-art performance on segmentation classification detection tasks with lower extra computational cost. Such as 90.7% on ScanObjectNN for classification 79.2% on S3DIS 6 fold and 74.3% on S3DIS Area 5 for segmentation 76.3% on ScanNetV2 for segmentation and 64.5% mAP_ 25 46.9% mAP_ 50 on SUN RGB-D and 69.0% mAP_ 25 51.1% mAP_ 50 on ScanNetV2 . Our code is available at \href https://github.com/sunshuofeng/X-3D https://github.com/sunshuofeng/X-3D .

Samar Fares, Karthik Nandakumar

Poisoning (trojan/backdoor) attacks enable an adversary to train and deploy a corrupted machine learning (ML) model which typically works well and achieves good accuracy on clean input samples but behaves maliciously on poisoned samples containing specific trigger patterns. Using such poisoned ML models as the foundation to build real-world systems can compromise application safety. Hence there is a critical need for algorithms that detect whether a given target model has been poisoned. This work proposes a novel approach for detecting poisoned models called Attack To Defend (A2D) which is based on the observation that poisoned models are more sensitive to adversarial perturbations compared to benign models. We propose a metric called sensitivity to adversarial perturbations (SAP) to measure the sensitivity of a ML model to adversarial attacks at a specific perturbation bound. We then generate strong adversarial attacks against an unrelated reference model and estimate the SAP value of the target model by transferring the generated attacks. The target model is deemed to be a trojan if its SAP value exceeds a decision threshold. The A2D framework requires only black-box access to the target model and a small clean set while being computationally efficient. The A2D approach has been evaluated on four standard image datasets and its effectiveness under various types of poisoning attacks has been demonstrated

Woo-Jin Ahn, Geun-Yeong Yang, Hyun-Duck Choi, Myo-Taeg Lim

Deep learning models for semantic segmentation often experience performance degradation when deployed to unseen target domains unidentified during the training phase. This is mainly due to variations in image texture (i.e. style) from different data sources. To tackle this challenge existing domain generalized semantic segmentation (DGSS) methods attempt to remove style variations from the feature. However these approaches struggle with the entanglement of style and content which may lead to the unintentional removal of crucial content information causing performance degradation. This study addresses this limitation by proposing BlindNet a novel DGSS approach that blinds the style without external modules or datasets. The main idea behind our proposed approach is to alleviate the effect of style in the encoder whilst facilitating robust segmentation in the decoder. To achieve this BlindNet comprises two key components: covariance alignment and semantic consistency contrastive learning. Specifically the covariance alignment trains the encoder to uniformly recognize various styles and preserve the content information of the feature rather than removing the style-sensitive factor. Meanwhile semantic consistency contrastive learning enables the decoder to construct discriminative class embedding space and disentangles features that are vulnerable to misclassification. Through extensive experiments our approach outperforms existing DGSS methods exhibiting robustness and superior performance for semantic segmentation on unseen target domains.

Mingdeng Cao, Sidi Yang, Yujiu Yang, Yinqiang Zheng

This paper proposes to correct the rolling shutter (RS) distorted images by estimating the distortion flow from the global shutter (GS) to RS directly. Existing methods usually perform correction using the undistortion flow from the RS to GS. They initially predict the flow from consecutive RS frames subsequently rescaling it as the displacement fields from the RS frame to the underlying GS image using time-dependent scaling factors. Following this RS-aware forward warping is employed to convert the RS image into its GS counterpart. Nevertheless this strategy is prone to two shortcomings. First the undistortion flow estimation is rendered inaccurate by merely linear scaling the flow due to the complex non-linear motion nature. Second RS-aware forward warping often results in unavoidable artifacts. To address these limitations we introduce a new framework that directly estimates the distortion flow and rectifies the RS image with the backward warping operation. More specifically we first propose a global correlation-based flow attention mechanism to estimate the initial distortion flow and GS feature jointly which are then refined by the following coarse-to-fine decoder layers. Additionally a multi-distortion flow prediction strategy is integrated to mitigate the issue of inaccurate flow estimation further. Experimental results validate the effectiveness of the proposed method which outperforms state-of-the-art approaches on various benchmarks while maintaining high efficiency. The project is available at https://github.com/ljzycmd/DFRSC.

Daniel Rebain, Soroosh Yazdani, Kwang Moo Yi, Andrea Tagliasacchi

Neural fields have emerged as a powerful and broadly applicable method for representing signals. However in contrast to classical discrete digital signal processing the portfolio of tools to process such representations is still severely limited and restricted to Euclidean domains. In this paper we address this problem by showing how a probabilistic re-interpretation of neural fields can enable their training and inference processes to become "filter-aware". The formulation we propose not only merges training and filtering in an efficient way but also generalizes beyond the familiar Euclidean coordinate spaces to the more general set of smooth manifolds and convolutions induced by the actions of Lie groups. We demonstrate how this framework can enable novel integrations of signal processing techniques for neural field applications on both Euclidean domains such as images and audio as well as non-Euclidean domains such as rotations and rays. A noteworthy benefit of our method is its applicability. Our method can be summarized as primarily a modification of the loss function and in most cases does not require changes to the network architecture or the inference process.

Zixiong Huang, Qi Chen, Libo Sun, Yifan Yang, Naizhou Wang, Qi Wu, Mingkui Tan

Novel view synthesis aims to generate new view images of a given view image collection. Recent attempts address this problem relying on 3D geometry priors (e.g. shapes sizes and positions) learned from multi-view images. However such methods encounter the following limitations: 1) they require a set of multi-view images as training data for a specific scene (e.g. face car or chair) which is often unavailable in many real-world scenarios; 2) they fail to extract the geometry priors from single-view images due to the lack of multi-view supervision. In this paper we propose a Geometry-enhanced NeRF (G-NeRF) which seeks to enhance the geometry priors by a geometry-guided multi-view synthesis approach followed by a depth-aware training. In the synthesis process inspired that existing 3D GAN models can unconditionally synthesize high-fidelity multi-view images we seek to adopt off-the-shelf 3D GAN models such as EG3D as a free source to provide geometry priors through synthesizing multi-view data. Simultaneously to further improve the geometry quality of the synthetic data we introduce a truncation method to effectively sample latent codes within 3D GAN models. To tackle the absence of multi-view supervision for single-view images we design the depth-aware training approach incorporating a depth-aware discriminator to guide geometry priors through depth maps. Experiments demonstrate the effectiveness of our method in terms of both qualitative and quantitative results.

Jianjian Cao, Peng Ye, Shengze Li, Chong Yu, Yansong Tang, Jiwen Lu, Tao Chen

Vision-Language Transformers (VLTs) have shown great success recently but are meanwhile accompanied by heavy computation costs where a major reason can be attributed to the large number of visual and language tokens. Existing token pruning research for compressing VLTs mainly follows a single-modality-based scheme yet ignores the critical role of aligning different modalities for guiding the token pruning process causing the important tokens for one modality to be falsely pruned in another modality branch. Meanwhile existing VLT pruning works also lack the flexibility to dynamically compress each layer based on different input samples. To this end we propose a novel framework named Multimodal Alignment-Guided Dynamic Token Pruning (MADTP) for accelerating various VLTs. Specifically we first introduce a well-designed Multi-modality Alignment Guidance (MAG) module that can align features of the same semantic concept from different modalities to ensure the pruned tokens are less important for all modalities. We further design a novel Dynamic Token Pruning (DTP) module which can adaptively adjust the token compression ratio in each layer based on different input instances. Extensive experiments on various benchmarks demonstrate that MADTP significantly reduces the computational complexity of kinds of multimodal models while preserving competitive performance. Notably when applied to the BLIP model in the NLVR2 dataset MADTP can reduce the GFLOPs by 80% with less than 4% performance degradation.

Yancong Lin, Holger Caesar

Scene flow characterizes the 3D motion between two LiDAR scans captured by an autonomous vehicle at nearby timesteps. Prevalent methods consider scene flow as point-wise unconstrained flow vectors that can be learned by either large-scale training beforehand or time-consuming optimization at inference. However these methods do not take into account that objects in autonomous driving often move rigidly. We incorporate this rigid-motion assumption into our design where the goal is to associate objects over scans and then estimate the locally rigid transformations. We propose ICP-Flow a learning-free flow estimator. The core of our design is the conventional Iterative Closest Point (ICP) algorithm which aligns the objects over time and outputs the corresponding rigid transformations. Crucially to aid ICP we propose a histogram-based initialization that discovers the most likely translation thus providing a good starting point for ICP. The complete scene flow is then recovered from the rigid transformations. We outperform state-of-the-art baselines including supervised models on the Waymo dataset and perform competitively on Argoverse-v2 and nuScenes. Further we train a feedforward neural network supervised by the pseudo labels from our model and achieve top performance among all models capable of real-time inference. We validate the advantage of our model on scene flow estimation with longer temporal gaps up to 0.4 seconds where other models fail to deliver meaningful results.

Abhisek Ray, Gaurav Kumar, Maheshkumar H. Kolekar

Transformer-based models have revolutionized the field of image super-resolution (SR) by harnessing their inherent ability to capture complex contextual features. The overlapping rectangular shifted window technique used in transformer architecture nowadays is a common practice in super-resolution models to improve the quality and robustness of image upscaling. However it suffers from distortion at the boundaries and has limited unique shifting modes. To overcome these weaknesses we propose a non-overlapping triangular window technique that synchronously works with the rectangular one to mitigate boundary-level distortion and allows the model to access more unique sifting modes. In this paper we propose a Composite Fusion Attention Transformer (CFAT) that incorporates triangular-rectangular window-based local attention with a channel-based global attention technique in image super-resolution. As a result CFAT enables attention mechanisms to be activated on more image pixels and captures long-range multi-scale features to improve SR performance. The extensive experimental results and ablation study demonstrate the effectiveness of CFAT in the SR domain. Our proposed model shows a significant 0.7 dB performance improvement over other state-of-the-art SR architectures.