自回归模型已被证明在NLP文本生成任务中非常强大，并且最近也获得了图像生成的普及。然而，到目前为止，它们已经有限地用于合成3D形状。这主要是由于在描述复杂形状时缺乏线性化3D数据的直接方法以及缩放所得序列的长度的问题。在这项工作中，我们解决了这两个问题。我们使用Octrees作为紧凑的层级表示，可以通过遍历排序顺序顺序。此外，我们引入了一种自适应压缩方案，显着降低了序列长度，从而使其具有变压器的有效发电，同时仍然允许完全自回归采样和并行训练。我们通过与现有形状的形式进行比较来展示我们模型的性能。

We advocate the use of implicit fields for learning generative models of shapes and introduce an implicit field decoder, called IM-NET, for shape generation, aimed at improving the visual quality of the generated shapes. An implicit field assigns a value to each point in 3D space, so that a shape can be extracted as an iso-surface. IM-NET is trained to perform this assignment by means of a binary classifier. Specifically, it takes a point coordinate, along with a feature vector encoding a shape, and outputs a value which indicates whether the point is outside the shape or not. By replacing conventional decoders by our implicit decoder for representation learning (via IM-AE) and shape generation (via IM-GAN), we demonstrate superior results for tasks such as generative shape modeling, interpolation, and single-view 3D reconstruction, particularly in terms of visual quality. Code and supplementary material are available at https://github.com/czq142857/implicit-decoder.

Designed to learn long-range interactions on sequential data, transformers continue to show state-of-the-art results on a wide variety of tasks. In contrast to CNNs, they contain no inductive bias that prioritizes local interactions. This makes them expressive, but also computationally infeasible for long sequences, such as high-resolution images. We demonstrate how combining the effectiveness of the inductive bias of CNNs with the expressivity of transformers enables them to model and thereby synthesize high-resolution images. We show how to (i) use CNNs to learn a contextrich vocabulary of image constituents, and in turn (ii) utilize transformers to efficiently model their composition within high-resolution images. Our approach is readily applied to conditional synthesis tasks, where both non-spatial information, such as object classes, and spatial information, such as segmentations, can control the generated image. In particular, we present the first results on semanticallyguided synthesis of megapixel images with transformers and obtain the state of the art among autoregressive models on class-conditional ImageNet. Code and pretrained models can be found at https://git.io/JnyvK.

生成建模研究的持续趋势是将样本分辨率推高更高，同时减少培训和采样的计算要求。我们的目标是通过技术的组合进一步推动这一趋势 - 每个组件代表当前效率在各自领域的顶峰。其中包括载体定量的GAN（VQ-GAN），该模型具有高水平的损耗 - 但感知上微不足道的压缩模型；沙漏变形金刚，一个高度可扩展的自我注意力模型；和逐步未胶片的denoising自动编码器（Sundae），一种非自动化（NAR）文本生成模型。出乎意料的是，当应用于多维数据时，我们的方法突出了沙漏变压器的原始公式中的弱点。鉴于此，我们建议对重采样机制进行修改，该机制适用于将分层变压器应用于多维数据的任何任务。此外，我们证明了圣代表到长序列长度的可伸缩性 - 比先前的工作长四倍。我们提出的框架秤达到高分辨率（$ 1024 \ times 1024 $），并迅速火车（2-4天）。至关重要的是，训练有素的模型在消费级GPU（GTX 1080TI）上大约2秒内生产多样化和现实的百像样品。通常，该框架是灵活的：支持任意数量的采样步骤，示例自动插入，自我纠正功能，有条件的生成和NAR公式，以允许任意介绍掩护。我们在FFHQ256上获得10.56的FID得分 - 仅在100个采样步骤中以不到一半的采样步骤接近原始VQ -GAN，而FFHQ1024的FFHQ1024和21.85。

We present a deep convolutional decoder architecture that can generate volumetric 3D outputs in a compute-and memory-efficient manner by using an octree representation. The network learns to predict both the structure of the octree, and the occupancy values of individual cells. This makes it a particularly valuable technique for generating 3D shapes. In contrast to standard decoders acting on regular voxel grids, the architecture does not have cubic complexity. This allows representing much higher resolution outputs with a limited memory budget. We demonstrate this in several application domains, including 3D convolutional autoencoders, generation of objects and whole scenes from high-level representations, and shape from a single image.

We present OctNet, a representation for deep learning with sparse 3D data. In contrast to existing models, our representation enables 3D convolutional networks which are both deep and high resolution. Towards this goal, we exploit the sparsity in the input data to hierarchically partition the space using a set of unbalanced octrees where each leaf node stores a pooled feature representation. This allows to focus memory allocation and computation to the relevant dense regions and enables deeper networks without compromising resolution. We demonstrate the utility of our OctNet representation by analyzing the impact of resolution on several 3D tasks including 3D object classification, orientation estimation and point cloud labeling.

Generative models, as an important family of statistical modeling, target learning the observed data distribution via generating new instances. Along with the rise of neural networks, deep generative models, such as variational autoencoders (VAEs) and generative adversarial network (GANs), have made tremendous progress in 2D image synthesis. Recently, researchers switch their attentions from the 2D space to the 3D space considering that 3D data better aligns with our physical world and hence enjoys great potential in practice. However, unlike a 2D image, which owns an efficient representation (i.e., pixel grid) by nature, representing 3D data could face far more challenges. Concretely, we would expect an ideal 3D representation to be capable enough to model shapes and appearances in details, and to be highly efficient so as to model high-resolution data with fast speed and low memory cost. However, existing 3D representations, such as point clouds, meshes, and recent neural fields, usually fail to meet the above requirements simultaneously. In this survey, we make a thorough review of the development of 3D generation, including 3D shape generation and 3D-aware image synthesis, from the perspectives of both algorithms and more importantly representations. We hope that our discussion could help the community track the evolution of this field and further spark some innovative ideas to advance this challenging task.

通常在特定对象类别的大型3D数据集上对3D形状的现有生成模型进行培训。在本文中，我们研究了仅从单个参考3D形状学习的深层生成模型。具体而言，我们提出了一个基于GAN的多尺度模型，旨在捕获一系列空间尺度的输入形状的几何特征。为了避免在3D卷上操作引起的大量内存和计算成本，我们在三平面混合表示上构建了我们的发电机，这仅需要2D卷积。我们在参考形状的体素金字塔上训练我们的生成模型，而无需任何外部监督或手动注释。一旦受过训练，我们的模型就可以产生不同尺寸和宽高比的多样化和高质量的3D形状。所得的形状会跨不同的尺度呈现变化，同时保留了参考形状的全局结构。通过广泛的评估，无论是定性还是定量，我们都证明了我们的模型可以生成各种类型的3D形状。

我们提出了一种新颖的生成方法，用于创建城市规模的路线。虽然最近方法的输出在覆盖区域的大小和多样性的尺寸上都受到限制，但我们的框架可产生大量的高质量遍历图，这些图形由顶点和边缘组成，这些边缘和边缘代表了覆盖400平方公里或更多的完整街道网络。尽管我们的框架可以处理一般的2D嵌入式图，但由于培训数据的广泛可用性，我们专注于街道网络。我们的生成框架由一个变压器解码器组成，该解码器以滑动窗口方式用于预测索引字段，每个索引编码本地邻域的表示形式。每个索引的语义由上下文向量的字典确定。然后将索引字段输入到解码器以计算街道图。使用OpenStreetMap的数据，我们在整个城市甚至在美国等大国中训练我们的系统，并最终将其与最新技术进行比较。

最近对变形金刚的爆炸利益提出了他们成为计算机视觉任务的强大“通用”模型的潜力，例如分类，检测和分割。虽然这些尝试主要研究歧视模型，但我们探索变压器，更加臭名昭着的难以愿景任务，例如生成的对抗网络（GANS）。我们的目标是通过仅使用纯的变压器的架构，开展一项完全没有卷曲的GAN的试点研究。我们的Vanilla GaN架构被称为Cransgan，包括一个基于内存友好的变换器的发电机，逐渐增加了特征分辨率，并且相应地是多尺度鉴别器来捕获同时语义上下文和低级纹理。在他们之上，我们介绍了新的网格自我关注模块，以便进一步缓解记忆瓶颈，以便扩展到高分辨率的发电。我们还开发了一个独特的培训配方，包括一系列技术，可以减轻转发的培训不稳定问题，例如数据增强，修改的归一化和相对位置编码。与使用卷积骨架的当前最先进的GAN相比，我们最好的建筑达到了竞争力的表现。具体而言，转发在STL-10上设置10.43和18.28的最新的最新成立得分为18.28，表现优于样式。当涉及更高分辨率（例如256 x 256）的生成任务时，例如Celeba-HQ和Lsun-Church，Rancorgan继续生产具有高保真度和令人印象深刻的纹理细节的不同视觉示例。此外，我们通过可视化培训动力学，深入了解基于变压器的生成模型，了解他们的行为如何与卷积的行为。代码可在https://github.com/vita-group/transgan中获得。

Compact and accurate representations of 3D shapes are central to many perception and robotics tasks. State-of-the-art learning-based methods can reconstruct single objects but scale poorly to large datasets. We present a novel recursive implicit representation to efficiently and accurately encode large datasets of complex 3D shapes by recursively traversing an implicit octree in latent space. Our implicit Recursive Octree Auto-Decoder (ROAD) learns a hierarchically structured latent space enabling state-of-the-art reconstruction results at a compression ratio above 99%. We also propose an efficient curriculum learning scheme that naturally exploits the coarse-to-fine properties of the underlying octree spatial representation. We explore the scaling law relating latent space dimension, dataset size, and reconstruction accuracy, showing that increasing the latent space dimension is enough to scale to large shape datasets. Finally, we show that our learned latent space encodes a coarse-to-fine hierarchical structure yielding reusable latents across different levels of details, and we provide qualitative evidence of generalization to novel shapes outside the training set.

现实世界中的数据是高维的：即使在压缩后，书籍，图像或音乐表演也很容易包含数十万个元素。但是，最常用的自回归模型，变压器非常昂贵，以缩放捕获这种远程结构所需的输入和层数。我们开发了感知者AR，这是一种自回归的模态 - 不合骨架构，它使用交叉注意力将远程输入映射到少数潜在的潜在，同时还可以维护端到端的因果关系掩盖。感知器AR可以直接进行十万个令牌，从而实现了实用的长篇小写密度估计，而无需手工制作的稀疏模式或记忆机制。当对图像或音乐进行培训时，感知器AR会生成具有清晰长期连贯性和结构的输出。我们的架构还获得了长期基准测试的最新可能性，包括64 x 64个Imagenet图像和PG-19书籍。

Point cloud completion is a generation and estimation issue derived from the partial point clouds, which plays a vital role in the applications in 3D computer vision. The progress of deep learning (DL) has impressively improved the capability and robustness of point cloud completion. However, the quality of completed point clouds is still needed to be further enhanced to meet the practical utilization. Therefore, this work aims to conduct a comprehensive survey on various methods, including point-based, convolution-based, graph-based, and generative model-based approaches, etc. And this survey summarizes the comparisons among these methods to provoke further research insights. Besides, this review sums up the commonly used datasets and illustrates the applications of point cloud completion. Eventually, we also discussed possible research trends in this promptly expanding field.

大多数现代深度学习的多视图3D重建技术都使用RNN或融合模块在独立编码之后将来自多个图像的信息组合在一起。这两个单独的步骤具有松散的连接，不允许在视图之间简化信息共享。我们提出了LegoFormer，这是一种基于体素的3D重建的变压器模型，该模型使用注意力层在所有计算阶段中共享视图之间的信息。此外，我们建议使用一系列低级分解因子来参数输出，而不是独立预测每个体素。该重新制定允许对象作为一组独立的常规结构进行预测，然后汇总以获得最终的重建。在Shapenet上进行的实验证明了我们模型在最新技术方面的竞争性能，同时由于自我发挥层而具有可解释性。我们还显示了对真实数据的有希望的概括结果。

我们提出了ShapeCrafter，这是一个用于递归文本条件3D形状生成的神经网络。生成文本条件的3D形状的现有方法会消耗整个文本提示，以在一个步骤中生成3D形状。但是，人类倾向于递归描述形状，我们可能以初始描述开始，并根据中间结果逐步添加细节。为了捕获此递归过程，我们引入了一种生成以初始短语为条件的3D形状分布的方法，该方法随着添加更多短语而逐渐发展。由于现有的数据集不足以训练这种方法，因此我们提出了Text2Shape ++，这是一个支持递归形状生成的369K形状文本对的大数据集。为了捕获通常用于完善形状描述的本地细节，我们建立在矢量定量的深层隐式函数的基础上，从而产生高质量形状的分布。结果表明，我们的方法可以生成与文本描述一致的形状，并且随着添加更多短语，形状逐渐发展。我们的方法支持形状编辑，外推，并可以在人机合作中为创意设计提供新的应用程序。

Three-dimensional geometric data offer an excellent domain for studying representation learning and generative modeling. In this paper, we look at geometric data represented as point clouds. We introduce a deep AutoEncoder (AE) network with state-of-the-art reconstruction quality and generalization ability. The learned representations outperform existing methods on 3D recognition tasks and enable shape editing via simple algebraic manipulations, such as semantic part editing, shape analogies and shape interpolation, as well as shape completion. We perform a thorough study of different generative models including GANs operating on the raw point clouds, significantly improved GANs trained in the fixed latent space of our AEs, and Gaussian Mixture Models (GMMs). To quantitatively evaluate generative models we introduce measures of sample fidelity and diversity based on matchings between sets of point clouds. Interestingly, our evaluation of generalization, fidelity and diversity reveals that GMMs trained in the latent space of our AEs yield the best results overall.

尽管神经场景表示的潜力能够在高重建质量下有效压缩3D标量场，但使用场景表示网络的训练和数据重建步骤的计算复杂性限制了它们在实际应用中的使用。在本文中，我们分析了是否可以修改场景表示网络以减少这些限制以及这些架构是否也可以用于时间重建任务。我们提出了一种使用GPU Tensor核心的场景表示网络设计，将重建无缝化为片上芯片的横梁内核。此外，我们调查使用图像引导网络培训作为典型数据驱动方法的替代方案，我们探索了这种替代品质量和速度的潜在优势和缺点。作为时变字段的空间超分辨率方法的替代方案，我们提出了一种在潜在空间插值上建立的解决方案，以使任意粒度的随机访问重建。我们以评估科学可视化任务和概述未来研究方向的现场代表网络的优势和局限性的形式总结了我们的调查结果。

本研究通过基于稀疏的张量处理（STP）的Voxelized PCG的多尺度表示，通过稀疏的张解器处理（STP）进行了一种统一点云几何形状（PCG）压缩方法。应用STP显着降低了复杂性，因为它只执行以最可能的积极占用体素（MP-POV）为中心的卷曲。并且多尺度代表有助于我们逐步压缩规模明智的MP-POV。总压缩效率高度取决于每个MP-POV的占用概率的近似精度。因此，我们设计基于稀疏的卷积的神经网络（Sparsecnn），包括稀疏卷曲和体素重新采样以广泛利用前沿。然后，我们开发基于SPARSECNN的占用概率近似（SOPA）模型，以估计在单阶段的方式中仅在逐步使用自回归邻居之前或以多阶段使用的横级或以多级的方式估计占用概率。此外，我们还建议基于SPARSECNN的本地邻居嵌入（SLNE），以表征当地空间变化作为改进SOPA的特征属性。我们的统一方法显示了在与MPEG G-PCC相比的各种数据集中，包括致密PCG（8iVFB，OWLII）和稀疏LIDAR PCG（KITTI，FORD）的各种数据集中的无损压缩模式中的最先进的性能和其他基于学习的压缩方案。此外，所提出的方法由于跨越所有尺度的模型共享而引起的轻量级复杂性，并且由于模型共享。我们使所有材料可在HTTPS://github.com/njuvision/sparsepcgc上公开访问可重复的研究。

虽然扩散概率模型可以产生高质量的图像内容，但仍然存在高分辨率图像的关键限制及其相关的高计算要求。最近的矢量量化图像模型已经克服了图像分辨率的这种限制，而是通过从之前的元素 - 明智的自回归采样生成令牌时，这是对图像分辨率的速度和单向的。相比之下，在本文中，我们提出了一种新的离散扩散概率模型，其通过使用无约束的变压器架构作为骨干来支持矢量量化令牌的并行预测。在培训期间，令牌以订单不可知的方式随机掩盖，变压器学会预测原始令牌。这种矢量量化令牌预测的并行性反过来促进了在计算费用的一小部分下的全球一致的高分辨率和多样性图像的无条件生成。以这种方式，我们可以产生超过原始训练集样本的图像分辨率，而另外提供每个图像似然估计（从生成的对抗方法的差点）。我们的方法在密度方面实现了最先进的结果（Lsun卧室：1.51; Lsun Churches：1.12; FFHQ：1.20）和覆盖范围（Lsun卧室：0.83; Lsun Churches：0.73; FFHQ：0.80），并执行竞争对手（LSUN卧室：3.64; LSUN教堂：4.07; FFHQ：6.11）在计算和减少训练套件要求方面提供优势。