New ideas for LiDAR simulation | LidarDM: Helps generate 4D world, simulation killer~

Original title: LidarDM: Generative LiDAR Simulation in a Generated World

Paper link: https://arxiv.org/pdf/2404.02903.pdf

Code link: https ://github.com/vzyrianov/lidardm

Author affiliation: University of Illinois, Massachusetts Institute of Technology

Thesis idea:

This article introduces LidarDM, a novel lidar generation model capable of producing realistic, layout-aware, physically believable, and temporally coherent lidar videos. LidarDM has two unprecedented capabilities in lidar generation modeling: (1) lidar generation guided by driving scenarios, providing significant incentives for autonomous driving simulations; (2) 4D lidar point cloud generation, enabling the creation of realistic and Temporally coherent lidar sequences are possible. The core of our model is a novel comprehensive 4D world generation framework. Specifically, this paper uses latent diffusion models to generate 3D scenes, combines them with dynamic actors to form the underlying 4D world, and then generates realistic laser perception data in this virtual environment. . Our experiments show that our method outperforms competing algorithms in terms of fidelity, temporal coherence, and layout consistency. This paper also demonstrates that LidarDM can be used as a generative world simulator for training and testing perception models.

Network Design:

The developed generative models have attracted increasing attention in handling data distribution and content creation, such as image and video generation [ 10, 33, 52-55], 3D object generation [10, 19, 38, 52], compression [5, 29, 68] and editing [37, 47] and other fields. Generative models also show excellent potential for simulation [6, 11, 18, 34, 46, 60, 64, 66, 76, 82], enabling the creation of realistic scenarios and their associated sensory data for training and evaluation of safety Critical intelligence capabilities, such as robots and self-driving vehicles, eliminate the need for costly manual modeling of the real world. These capabilities are critical for applications that rely on extensive environmental training or scenario testing.

Progress in conditional image and video generation has been remarkable, but the specific task of generating realistic lidar point cloud sequences for functionally specific scenarios for autonomous driving applications remains underexplored. Current lidar generation methods fall into two main categories, each of which faces specific challenges.

1. Current lidar generation modeling methods [8, 72, 79, 83] are limited to single-frame generation and do not provide means for semantic controllability and temporal consistency.
2. LiDAR resimulation [14, 17, 46, 65, 67, 74] relies heavily on user-created or real-world collected assets. This adds high operating costs, limits diversity, and limits wider applicability.

To address these challenges, this paper proposes LidarDM (Lidar Diffusion Model), which can create realistic, layout-aware, physically believable, and temporally coherent lidar videos. . This paper explores two novel capabilities that have not been addressed before: (i) lidar synthesis guided by driving scenarios, which has great potential for autonomous driving simulation, and (ii) aiming to produce realistic, annotated lidar point clouds Sequential 4D lidar point cloud synthesis. The key insight in achieving these goals in this paper lies in first generating and combining the underlying 4D world and then creating realistic perceptual observations within this virtual environment. To achieve this, this paper integrates existing 3D object generation methods to create dynamic actors and develops a new method for large-scale 3D scene generation based on latent diffusion models. This approach is capable of producing realistically diverse 3D driving scenes from the semantic layout of particles, and to the best of the knowledge of this paper, it is the first attempt. This article applies trajectories to generate a 3D world and performs stochastic raycasting simulation to generate the final 4D lidar sequence. As shown in Figure 1, the results generated in this paper are diverse, aligned with the layout conditions, and are both realistic and temporally coherent.

The experimental results of this paper show that single-frame images generated by LidarDM exhibit realism and diversity, and their performance is comparable to the state-of-the-art stripe-free single-frame laser point cloud generation technology. Furthermore, this paper demonstrates that LidarDM is capable of producing temporally coherent laser point cloud videos, beyond the robust diffusion sensor generation baseline. To the best of our knowledge, this is the first laser point cloud generation method with this capability. This paper further demonstrates the item generation capabilities of LidarDM by demonstrating good agreement between the generated laser point cloud and the real laser point cloud under matching map items. Finally, this paper demonstrates that data generated using LidarDM exhibit minimal domain gaps when tested with perception modules trained on real data, and can also be used to extend the training data, significantly improving the performance of 3D detectors. This provides a prerequisite for using the generated laser point cloud model to create a realistic and controllable simulation environment for training and testing driving models.

Figure 1: This paper demonstrates LidarDM, a novel 4D lidar generative model. The lidar video generated in this article has the advantages of realism, layout conditionality, physical credibility, diversity and temporal coherence at the same time.

Figure 2: Application of LidarDM: (a) Generating lidar closely aligned with the map without 3D capture or modeling (colored box highlights lidar consistency with maps); (b) provide sensor data to an existing traffic simulator (Waymax [20]), enabling it to evaluate safety-critical scenarios from pure sensor data only; (c) generate traffic with controllable obstacles Large amounts of lidar data of object locations (considered as freely available ground truth labels) to improve perception models through pre-training without expensive data capture and annotation.

Figure 3: LidarDM Overview: Given the traffic layout input at time t = 0, LidarDM first generates traffic participants (actors) and static scenes. Then, this article generates the movements of traffic participants (actors) and self-vehicles, and builds the underlying 4D world. Finally, use generative and physics-based simulation to create realistic 4D sensor data.

Figure 4: The 3D scene generation process of this article. First, the accumulated point cloud is used to reconstruct each real mesh sample. Next, a variational autoencoder (VAE) is trained to compress the grid into an implicit encoding. Finally, a diffusion model conditioned on the map is trained to sample within the latent space of the VAE to generate new samples.

Figure 5: Random raydrop network for perceptual noise simulation, further enhancing realism. This article highlights raydropped points in red in the masked distance map and masked lidar image above.

Experimental results:

Figure 6: Real KITTI-360 samples compared to unconditioned samples from competing methods. UltraLiDAR sample visualizations are taken directly from their paper. Compared to previous methods, LidarDM generates samples with a greater number of more detailed salient objects (e.g., cars, pedestrians), clearer 3D structures (e.g., straight walls), and a more realistic road layout.

Figure 7: Qualitative results of map-conditioned sequence generation on 2 Waymax [20] map sequences. This paper also shows the corresponding cumulative point cloud to highlight the temporal consistency of LidarDM.

Summary:

This paper proposes LidarDM, which is a novel layout-based Conditional latent diffusion models for generating realistic lidar point clouds. Our approach frames the problem as a joint 4D world creation and perception data generation task, and develops a novel latent diffusion model to create 3D scenes. The resulting point cloud video is realistic, coherent, and layout-aware.

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