CVPR 2024 Papers

Real driving-video dehazing poses a significant challenge due to the inherent difficulty in acquiring precisely aligned hazy/clear video pairs for effective model training especially in dynamic driving scenarios with unpredictable weather conditions. In this paper we propose a pioneering approach that addresses this challenge through a nonaligned regularization strategy. Our core concept involves identifying clear frames that closely match hazy frames serving as references to supervise a video dehazing network. Our approach comprises two key components: reference matching and video dehazing. Firstly we introduce a non-aligned reference frame matching module leveraging an adaptive sliding window to match high-quality reference frames from clear videos. Video dehazing incorporates flow-guided cosine attention sampler and deformable cosine attention fusion modules to enhance spatial multiframe alignment and fuse their improved information. To validate our approach we collect a GoProHazy dataset captured effortlessly with GoPro cameras in diverse rural and urban road environments. Extensive experiments demonstrate the superiority of the proposed method over current state-of-the-art methods in the challenging task of real driving-video dehazing. Project page.

In autonomous driving predicting future events in advance and evaluating the foreseeable risks empowers autonomous vehicles to plan their actions enhancing safety and efficiency on the road. To this end we propose Drive-WM the first driving world model compatible with existing end-to-end planning models. Through a joint spatial-temporal modeling facilitated by view factorization our model is the first to generate high-fidelity multiview videos. Building on its powerful generation ability we showcase the potential of applying the world model for safe driving planning for the first time. Our Drive-WM enables driving into multiple futures based on distinct driving maneuvers and determines the optimal trajectory according to the image-based rewards. Evaluation on real-world driving datasets verifies that our method could generate high-quality consistent and controllable multiview videos opening up possibilities for real-world simulations and safe planning.

Adapting driving behavior to new environments customs and laws is a long-standing problem in autonomous driving precluding the widespread deployment of autonomous vehicles (AVs). In this paper we present LLaDA a simple yet powerful tool that enables human drivers and autonomous vehicles alike to drive everywhere by adapting their tasks and motion plans to traffic rules in new locations. LLaDA achieves this by leveraging the impressive zero-shot generalizability of large language models (LLMs) in interpreting the traffic rules in the local driver handbook. Through an extensive user study we show that LLaDA's instructions are useful in disambiguating in-the-wild unexpected situations. We also demonstrate LLaDA's ability to adapt AV motion planning policies in real-world datasets; LLaDA outperforms baseline planning approaches on all our metrics. Please check our website for more details: https://boyiliee.github.io/llada.

This paper presents DriveTrack a new benchmark and data generation framework for long-range keypoint tracking in real-world videos. DriveTrack is motivated by the observation that the accuracy of state-of-the-art trackers depends strongly on visual attributes around the selected keypoints such as texture and lighting. The problem is that these artifacts are especially pronounced in real-world videos but these trackers are unable to train on such scenes due to a dearth of annotations. DriveTrack bridges this gap by building a framework to automatically annotate point tracks on autonomous driving datasets. We release a dataset consisting of 1 billion point tracks across 24 hours of video which is seven orders of magnitude greater than prior real-world benchmarks and on par with the scale of synthetic benchmarks. DriveTrack unlocks new use cases for point tracking in real-world videos. First we show that fine-tuning keypoint trackers on DriveTrack improves accuracy on real-world scenes by up to 7%. Second we analyze the sensitivity of trackers to visual artifacts in real scenes and motivate the idea of running assistive keypoint selectors alongside trackers.

Large pretrained models are increasingly crucial in modern computer vision tasks. These models are typically used in downstream tasks by end-to-end finetuning which is highly memory-intensive for tasks with high-resolution data e.g. video understanding small object detection and point cloud analysis. In this paper we propose Dynamic Reversible Dual-Residual Networks or Dr2Net a novel family of network architectures that acts as a surrogate network to finetune a pretrained model with substantially reduced memory consumption. Dr2Net contains two types of residual connections one maintaining the residual structure in the pretrained models and the other making the network reversible. Due to its reversibility intermediate activations which can be reconstructed from output are cleared from memory during training. We use two coefficients on either type of residual connections respectively and introduce a dynamic training strategy that seamlessly transitions the pretrained model to a reversible network with much higher numerical precision. We evaluate Dr2Net on various pretrained models and various tasks and show that it can reach comparable performance to conventional finetuning but with significantly less memory usage.

StyleGAN has shown remarkable performance in unconditional image generation. However its high computational cost poses a significant challenge for practical applications. Although recent efforts have been made to compress StyleGAN while preserving its performance existing compressed models still lag behind the original model particularly in terms of sample diversity. To overcome this we propose a novel channel pruning method that leverages varying sensitivities of channels to latent vectors which is a key factor in sample diversity. Specifically by assessing channel importance based on their sensitivities to latent vector perturbations our method enhances the diversity of samples in the compressed model. Since our method solely focuses on the channel pruning stage it has complementary benefits with prior training schemes without additional training cost. Extensive experiments demonstrate that our method significantly enhances sample diversity across various datasets. Moreover in terms of FID scores our method not only surpasses state-of-the-art by a large margin but also achieves comparable scores with only half training iterations.

Facial Attribute Classification (FAC) holds substantial promise in widespread applications. However FAC models trained by traditional methodologies can be unfair by exhibiting accuracy inconsistencies across varied data subpopulations. This unfairness is largely attributed to bias in data where some spurious attributes (e.g. Male) statistically correlate with the target attribute (e.g. Smiling). Most of existing fairness-aware methods rely on the labels of spurious attributes which may be unavailable in practice. This work proposes a novel generation-based two-stage framework to train a fair FAC model on biased data without additional annotation. Initially we identify the potential spurious attributes based on generative models. Notably it enhances interpretability by explicitly showing the spurious attributes in image space. Following this for each image we first edit the spurious attributes with a random degree sampled from a uniform distribution while keeping target attribute unchanged. Then we train a fair FAC model by fostering model invariance to these augmentation. Extensive experiments on three common datasets demonstrate the effectiveness of our method in promoting fairness in FAC without compromising accuracy. Codes are in https://github.com/heqianpei/DiGA.

Lifelong person re-identification (LReID) suffers from the catastrophic forgetting problem when learning from non-stationary data. Existing exemplar-based and knowledge distillation-based LReID methods encounter data privacy and limited acquisition capacity respectively. In this paper we instead introduce the prototype which is under-investigated in LReID to better balance knowledge forgetting and acquisition. Existing prototype-based works primarily focus on the classification task where the prototypes are set as discrete points or statistical distributions. However they either discard the distribution information or omit instance-level diversity which are crucial fine-grained clues for LReID. To address the above problems we propose Distribution-aware Knowledge Prototyping (DKP) where the instance-level diversity of each sample is modeled to transfer comprehensive fine-grained knowledge for prototyping and facilitating LReID learning. Specifically an Instance-level Distribution Modeling network is proposed to capture the local diversity of each instance. Then the Distribution-oriented Prototype Generation algorithm transforms the instance-level diversity into identity-level distributions as prototypes which is further explored by the designed Prototype-based Knowledge Transfer module to enhance the knowledge anti-forgetting and acquisition capacity of the LReID model. Extensive experiments verify that our method achieves superior plasticity and stability balancing and outperforms existing LReID methods by 8.1%/9.1% average mAP/R@1 improvement. The code is available at https://github.com/zhoujiahuan1991/CVPR2024-DKP

Diffusion models have achieved great success in synthesizing high-quality images. However generating high-resolution images with diffusion models is still challenging due to the enormous computational costs resulting in a prohibitive latency for interactive applications. In this paper we propose DistriFusion to tackle this problem by leveraging parallelism across multiple GPUs. Our method splits the model input into multiple patches and assigns each patch to a GPU. However naively implementing such an algorithm breaks the interaction between patches and loses fidelity while incorporating such an interaction will incur tremendous communication overhead. To overcome this dilemma we observe the high similarity between the input from adjacent diffusion steps and propose Displaced Patch Parallelism which takes advantage of the sequential nature of the diffusion process by reusing the pre-computed feature maps from the previous timestep to provide context for the current step. Therefore our method supports asynchronous communication which can be pipelined by computation. Extensive experiments show that our method can be applied to recent Stable Diffusion XL with no quality degradation and achieve up to a 6.1x speedup on eight NVIDIA A100s compared to one. Our code is publicly available at https://github.com/mit-han-lab/distrifuser.

Hyperspectral 3D imaging aims to acquire both depth and spectral information of a scene. However existing methods are either prohibitively expensive and bulky or compromise on spectral and depth accuracy. In this paper we present Dispersed Structured Light (DSL) a cost-effective and compact method for accurate hyperspectral 3D imaging. DSL modifies a traditional projector-camera system by placing a sub-millimeter thick diffraction grating film front of the projector. This configuration enables dispersing structured light based on light wavelength. To utilize the dispersed structured light we devise a model for dispersive projection image formation and a per-pixel hyperspectral 3D reconstruction method. We validate DSL by instantiating a compact experimental prototype. DSL achieves spectral accuracy of 18.8nm full-width half-maximum (FWHM) and depth error of 1mm outperforming prior work on practical hyperspectral 3D imaging. DSL promises accurate and practical hyperspectral 3D imaging for diverse application domains including computer vision and graphics cultural heritage geology and biology.

Out-of-distribution (OOD) detection is essential for deploying machine learning models in open-world environments. Activation-based methods are a key approach in OOD detection working to mitigate overconfident predictions of OOD data. These techniques rectifying anomalous activations enhancing the distinguishability between in-distribution (ID) data and OOD data. However they assume by default that every channel is necessary for OOD detection and rectify anomalous activations in each channel. Empirical evidence has shown that there is a significant difference among various channels in OOD detection and discarding some channels can greatly enhance the performance of OOD detection. Based on this insight we propose \underline D iscriminability-\underline D riven \underline C hannel \underline S election (DDCS) which leverages an adaptive channel selection by estimating the discriminative score of each channel to boost OOD detection. The discriminative score takes inter-class similarity and inter-class variance of training data into account. However the estimation of discriminative score itself is susceptible to anomalous activations. To better estimate score we pre-rectify anomalous activations for each channel mildly. The experimental results show that DDCS achieves state-of-the-art performance on CIFAR and ImageNet-1K benchmarks. Moreover DDCS can generalize to different backbones and OOD scores.

We present a simple yet effective technique to estimate lighting in a single input image. Current techniques rely heavily on HDR panorama datasets to train neural networks to regress an input with limited field-of-view to a full environment map. However these approaches often struggle with real-world uncontrolled settings due to the limited diversity and size of their datasets. To address this problem we leverage diffusion models trained on billions of standard images to render a chrome ball into the input image. Despite its simplicity this task remains challenging: the diffusion models often insert incorrect or inconsistent objects and cannot readily generate chrome balls in HDR format. Our research uncovers a surprising relationship between the appearance of chrome balls and the initial diffusion noise map which we utilize to consistently generate high-quality chrome balls. We further fine-tune an LDR diffusion model (Stable Diffusion XL) with LoRA enabling it to perform exposure bracketing for HDR light estimation. Our method produces convincing light estimates across diverse settings and demonstrates superior generalization to in-the-wild scenarios.

DiffusionAvatars synthesizes a high-fidelity 3D head avatar of a person offering intuitive control over both pose and expression. We propose a diffusion-based neural renderer that leverages generic 2D priors to produce compelling images of faces. For coarse guidance of the expression and head pose we render a neural parametric head model (NPHM) from the target viewpoint which acts as a proxy geometry of the person. Additionally to enhance the modeling of intricate facial expressions we condition DiffusionAvatars directly on the expression codes obtained from NPHM via cross-attention. Finally to synthesize consistent surface details across different viewpoints and expressions we rig learnable spatial features to the head's surface via TriPlane lookup in NPHM's canonical space. We train DiffusionAvatars on RGB videos and corresponding fitted NPHM meshes of a person and test the obtained avatars in both self-reenactment and animation scenarios. Our experiments demonstrate that DiffusionAvatars generates temporally consistent and visually appealing videos for novel poses and expressions of a person outperforming existing approaches.

Diffusion models excel at modeling complex and multimodal trajectory distributions for decision-making and control. Reward-gradient guided denoising has been recently proposed to generate trajectories that maximize both a differentiable reward function and the likelihood under the data distribution captured by a diffusion model. Reward-gradient guided denoising requires a differentiable reward function fitted to both clean and noised samples limiting its applicability as a general trajectory optimizer. In this paper we propose DiffusionES a method that combines gradient-free optimization with trajectory denoising to optimize black-box non-differentiable objectives while staying in the data manifold. Diffusion-ES samples trajectories during evolutionary search from a diffusion model and scores them using a black-box reward function. It mutates high-scoring trajectories using a truncated diffusion process that applies a small number of noising and denoising steps allowing for much more efficient exploration of the solution space. We show that DiffusionES achieves state-of-the-art performance on nuPlan an established closed-loop planning benchmark for autonomous driving. Diffusion-ES outperforms existing sampling-based planners reactive deterministic or diffusion-based policies and reward-gradient guidance. Additionally we show that unlike prior guidance methods our method can optimize non-differentiable language-shaped reward functions generated by few-shot LLM prompting. When guided by a human teacher that issues instructions to follow our method can generate novel highly complex behaviors such as aggressive lane weaving which are not present in the training data. This allows us to solve the hardest nuPlan scenarios which are beyond the capabilities of existing trajectory optimization methods and driving policies.

Diffusion handles is a novel approach to enable 3D object edits on diffusion images requiring only existing pre-trained diffusion models depth estimation without any fine-tuning or 3D object retrieval. The edited results remain plausible photo-real and preserve object identity. Diffusion handles address a critically missing facet of generative image-based creative design. Our key insight is to lift diffusion activations for a selected object to 3D using a proxy depth 3D-transform the depth and associated activations and project them back to image space. The diffusion process guided by the manipulated activations produces plausible edited images showing complex 3D occlusion and lighting effects. We evaluate diffusion handles: quantitatively on a large synthetic data benchmark; and qualitatively by a user study showing our output to be more plausible and better than prior art at both 3D editing and identity control.

We describe a method for recovering the irradiance underlying a collection of images corrupted by atmospheric turbulence. Since supervised data is often technically impossible to obtain assumptions and biases have to be imposed to solve this inverse problem and we choose to model them explicitly. Rather than initializing a latent irradiance ("template") by heuristics to estimate deformation we select one of the images as a reference and model the deformation in this image by the aggregation of the optical flow from it to other images exploiting a prior imposed by Central Limit Theorem. Then with a novel flow inversion module the model registers each image TO the template but WITHOUT the template avoiding artifacts related to poor template initialization. To illustrate the robustness of the method we simply (i) select the first frame as the reference and (ii) use the simplest optical flow to estimate the warpings yet the improvement in registration is decisive in the final reconstruction as we achieve state-of-the-art performance despite its simplicity. The method establishes a strong baseline that can be further improved by integrating it seamlessly into more sophisticated pipelines or with domain-specific methods if so desired.

Existing diffusion models for pose-guided human video generation mostly suffer from temporal inconsistency in the generated appearance and poses due to the inherent randomization nature of the generation process. In this paper we propose a novel framework DiffPerformer to synthesize high-fidelity and temporally consistent human video. Without complex architecture modification or costly training DiffPerformer finetunes a pretrained diffusion model on a single video of the target character and introduces an implicit video representation as a proxy to learn temporally consistent guidance for the diffusion model. The guidance is encoded into VAE latent space and an iterative optimization loop is constructed between the implicit video representation and the diffusion model allowing to harness the smooth property of the implicit video representation and the generative capabilities of the diffusion model in a mutually beneficial way. Moreover we propose 3D-aware human flow as a temporal constraint during the optimization to explicitly model the correspondence between driving poses and human appearance. This alleviates the misalignment between guided poses and target performer and therefore maintains the appearance coherence under various motions. Extensive experiments demonstrate that our method outperforms the state-of-the-art methods.