Neural Radiance Fields (NeRF) have demonstrated superior novel view synthesis performance but are slow at rendering. To speed up the volume rendering process, many acceleration methods have been proposed at the cost of large memory consumption. To push the frontier of the efficiency-memory trade-off, we explore a new perspective to accelerate NeRF rendering, leveraging a key fact that the viewpoint change is usually smooth and continuous in interactive viewpoint control. This allows us to leverage the information of preceding viewpoints to reduce the number of rendered pixels as well as the number of sampled points along the ray of the remaining pixels. In our pipeline, a low-resolution feature map is rendered first by volume rendering, then a lightweight 2D neural renderer is applied to generate the output image at target resolution leveraging the features of preceding and current frames. We show that the proposed method can achieve competitive rendering quality while reducing the rendering time with little memory overhead, enabling 30FPS at 1080P image resolution with a low memory footprint.

本文旨在减少透明辐射场的渲染时间。一些最近的作品用图像编码器配备了神经辐射字段，能够跨越场景概括，这避免了每场景优化。但是，它们的渲染过程通常很慢。主要因素是，在推断辐射场时，它们在空间中的大量点。在本文中，我们介绍了一个混合场景表示，它结合了最佳的隐式辐射场和显式深度映射，以便有效渲染。具体地，我们首先构建级联成本量，以有效地预测场景的粗糙几何形状。粗糙几何允许我们在场景表面附近的几个点来样，并显着提高渲染速度。该过程是完全可疑的，使我们能够仅从RGB图像共同学习深度预测和辐射现场网络。实验表明，该方法在DTU，真正的前瞻性和NERF合成数据集上展示了最先进的性能，而不是比以前的最可推广的辐射现场方法快至少50倍。我们还展示了我们的方法实时综合动态人类执行者的自由观点视频。代码将在https://zju3dv.github.io/enerf/处提供。

我们提出了HRF-NET，这是一种基于整体辐射场的新型视图合成方法，该方法使用一组稀疏输入来呈现新视图。最近的概括视图合成方法还利用了光辉场，但渲染速度不是实时的。现有的方法可以有效地训练和呈现新颖的观点，但它们无法概括地看不到场景。我们的方法解决了用于概括视图合成的实时渲染问题，并由两个主要阶段组成：整体辐射场预测指标和基于卷积的神经渲染器。该架构不仅基于隐式神经场的一致场景几何形状，而且还可以使用单个GPU有效地呈现新视图。我们首先在DTU数据集的多个3D场景上训练HRF-NET，并且网络只能仅使用光度损耗就看不见的真实和合成数据产生合理的新视图。此外，我们的方法可以利用单个场景的密集参考图像集来产生准确的新颖视图，而无需依赖其他明确表示，并且仍然保持了预训练模型的高速渲染。实验结果表明，HRF-NET优于各种合成和真实数据集的最先进的神经渲染方法。

我们呈现NERF-SR，一种用于高分辨率（HR）新型视图合成的解决方案，主要是低分辨率（LR）输入。我们的方法是基于神经辐射场（NERF）的内置，其预测每点密度和颜色，具有多层的射击。在在任意尺度上产生图像时，NERF与超越观察图像的分辨率努力。我们的关键识别是NERF具有本地之前的，这意味着可以在附近区域传播3D点的预测，并且保持准确。我们首先通过超级采样策略来利用它，该策略在每个图像像素处射击多个光线，这在子像素级别强制了多视图约束。然后，我们表明，NERF-SR可以通过改进网络进一步提高超级采样的性能，该细化网络利用估计的深度来实现HR参考图像上的相关补丁的幻觉。实验结果表明，NERF-SR在合成和现实世界数据集的HR上为新型视图合成产生高质量结果。

Recent efforts in Neural Rendering Fields (NeRF) have shown impressive results on novel view synthesis by utilizing implicit neural representation to represent 3D scenes. Due to the process of volumetric rendering, the inference speed for NeRF is extremely slow, limiting the application scenarios of utilizing NeRF on resource-constrained hardware, such as mobile devices. Many works have been conducted to reduce the latency of running NeRF models. However, most of them still require high-end GPU for acceleration or extra storage memory, which is all unavailable on mobile devices. Another emerging direction utilizes the neural light field (NeLF) for speedup, as only one forward pass is performed on a ray to predict the pixel color. Nevertheless, to reach a similar rendering quality as NeRF, the network in NeLF is designed with intensive computation, which is not mobile-friendly. In this work, we propose an efficient network that runs in real-time on mobile devices for neural rendering. We follow the setting of NeLF to train our network. Unlike existing works, we introduce a novel network architecture that runs efficiently on mobile devices with low latency and small size, i.e., saving $15\times \sim 24\times$ storage compared with MobileNeRF. Our model achieves high-resolution generation while maintaining real-time inference for both synthetic and real-world scenes on mobile devices, e.g., $18.04$ms (iPhone 13) for rendering one $1008\times756$ image of real 3D scenes. Additionally, we achieve similar image quality as NeRF and better quality than MobileNeRF (PSNR $26.15$ vs. $25.91$ on the real-world forward-facing dataset).

In this paper, we present a novel and effective framework, named 4K-NeRF, to pursue high fidelity view synthesis on the challenging scenarios of ultra high resolutions, building on the methodology of neural radiance fields (NeRF). The rendering procedure of NeRF-based methods typically relies on a pixel wise manner in which rays (or pixels) are treated independently on both training and inference phases, limiting its representational ability on describing subtle details especially when lifting to a extremely high resolution. We address the issue by better exploring ray correlation for enhancing high-frequency details benefiting from the use of geometry-aware local context. Particularly, we use the view-consistent encoder to model geometric information effectively in a lower resolution space and recover fine details through the view-consistent decoder, conditioned on ray features and depths estimated by the encoder. Joint training with patch-based sampling further facilitates our method incorporating the supervision from perception oriented regularization beyond pixel wise loss. Quantitative and qualitative comparisons with modern NeRF methods demonstrate that our method can significantly boost rendering quality for retaining high-frequency details, achieving the state-of-the-art visual quality on 4K ultra-high-resolution scenario. Code Available at \url{https://github.com/frozoul/4K-NeRF}

We introduce a method to render Neural Radiance Fields (NeRFs) in real time using PlenOctrees, an octree-based 3D representation which supports view-dependent effects. Our method can render 800×800 images at more than 150 FPS, which is over 3000 times faster than conventional NeRFs. We do so without sacrificing quality while preserving the ability of NeRFs to perform free-viewpoint rendering of scenes with arbitrary geometry and view-dependent effects. Real-time performance is achieved by pre-tabulating the NeRF into a PlenOctree. In order to preserve viewdependent effects such as specularities, we factorize the appearance via closed-form spherical basis functions. Specifically, we show that it is possible to train NeRFs to predict a spherical harmonic representation of radiance, removing the viewing direction as an input to the neural network. Furthermore, we show that PlenOctrees can be directly optimized to further minimize the reconstruction loss, which leads to equal or better quality compared to competing methods. Moreover, this octree optimization step can be used to reduce the training time, as we no longer need to wait for the NeRF training to converge fully. Our real-time neural rendering approach may potentially enable new applications such as 6-DOF industrial and product visualizations, as well as next generation AR/VR systems. PlenOctrees are amenable to in-browser rendering as well; please visit the project page for the interactive online demo, as well as video and code: https://alexyu. net/plenoctrees.

神经辐射场（NERFS）表现出惊人的能力，可以从新颖的观点中综合3D场景的图像。但是，他们依赖于基于射线行进的专门体积渲染算法，这些算法与广泛部署的图形硬件的功能不匹配。本文介绍了基于纹理多边形的新的NERF表示形式，该表示可以有效地与标准渲染管道合成新型图像。 NERF表示为一组多边形，其纹理代表二进制不相处和特征向量。用Z-Buffer对多边形的传统渲染产生了每个像素的图像，该图像由在片段着色器中运行的小型，观点依赖的MLP来解释，以产生最终的像素颜色。这种方法使NERF可以使用传统的Polygon栅格化管道渲染，该管道提供了庞大的像素级并行性，从而在包括移动电话在内的各种计算平台上实现了交互式帧速率。

潜水员在NERF的关键思想和其变体 - 密度模型和体积渲染的关键思想中建立 - 学习可以从少量图像实际渲染的3D对象模型。与所有先前的NERF方法相比，潜水员使用确定性而不是体积渲染积分的随机估计。潜水员的表示是基于体素的功能领域。为了计算卷渲染积分，将光线分为间隔，每个体素;使用MLP的每个间隔的特征估计体渲染积分的组件，并且组件聚合。结果，潜水员可以呈现其他集成商错过的薄半透明结构。此外，潜水员的表示与其他这样的方法相比相对暴露的语义 - 在体素空间中的运动特征向量导致自然编辑。对当前最先进的方法的广泛定性和定量比较表明，潜水员产生（1）在最先进的质量或高于最先进的质量，（2）的情况下非常小而不会被烘烤，（3）在不被烘烤的情况下渲染非常快，并且（4）可以以自然方式编辑。

神经辐射场（NERF）在代表3D场景和合成新颖视图中示出了很大的潜力，但是在推理阶段的NERF的计算开销仍然很重。为了减轻负担，我们进入了NERF的粗细分，分层采样过程，并指出粗阶段可以被我们命名神经样本场的轻量级模块代替。所提出的示例场地图光线进入样本分布，可以将其转换为点坐标并进料到radiance字段以进行体积渲染。整体框架被命名为Neusample。我们在现实合成360 $ ^ {\ circ} $和真正的前瞻性，两个流行的3D场景集上进行实验，并表明Neusample在享受更快推理速度时比NERF实现更好的渲染质量。Neusample进一步压缩，以提出的样品场提取方法朝向质量和速度之间的更好的权衡。

3D reconstruction and novel view synthesis of dynamic scenes from collections of single views recently gained increased attention. Existing work shows impressive results for synthetic setups and forward-facing real-world data, but is severely limited in the training speed and angular range for generating novel views. This paper addresses these limitations and proposes a new method for full 360{\deg} novel view synthesis of non-rigidly deforming scenes. At the core of our method are: 1) An efficient deformation module that decouples the processing of spatial and temporal information for acceleration at training and inference time; and 2) A static module representing the canonical scene as a fast hash-encoded neural radiance field. We evaluate the proposed approach on the established synthetic D-NeRF benchmark, that enables efficient reconstruction from a single monocular view per time-frame randomly sampled from a full hemisphere. We refer to this form of inputs as monocularized data. To prove its practicality for real-world scenarios, we recorded twelve challenging sequences with human actors by sampling single frames from a synchronized multi-view rig. In both cases, our method is trained significantly faster than previous methods (minutes instead of days) while achieving higher visual accuracy for generated novel views. Our source code and data is available at our project page https://graphics.tu-bs.de/publications/kappel2022fast.

Volumetric neural rendering methods like NeRF generate high-quality view synthesis results but are optimized per-scene leading to prohibitive reconstruction time. On the other hand, deep multi-view stereo methods can quickly reconstruct scene geometry via direct network inference. Point-NeRF combines the advantages of these two approaches by using neural 3D point clouds, with associated neural features, to model a radiance field. Point-NeRF can be rendered efficiently by aggregating neural point features near scene surfaces, in a ray marching-based rendering pipeline. Moreover, Point-NeRF can be initialized via direct inference of a pre-trained deep network to produce a neural point cloud; this point cloud can be finetuned to surpass the visual quality of NeRF with 30X faster training time. Point-NeRF can be combined with other 3D reconstruction methods and handles the errors and outliers in such methods via a novel pruning and growing mechanism. The experiments on the DTU, the NeRF Synthetics , the ScanNet and the Tanks and Temples datasets demonstrate Point-NeRF can surpass the existing methods and achieve the state-of-the-art results.

我们提出了一种可区分的渲染算法，以进行有效的新型视图合成。通过偏离基于音量的表示，支持学习点表示，我们在训练和推理方面的内存和运行时范围内改进了现有方法的数量级。该方法从均匀采样的随机点云开始，并使用基于可区分的SPLAT渲染器来发展模型以匹配一组输入图像，从而学习了每点位置和观看依赖性外观。在训练和推理中，我们的方法比NERF快300倍，质量只有边缘牺牲，而在静态场景中使用少于10 〜MB的记忆。对于动态场景，我们的方法比Stnerf训练两个数量级，并以接近互动速率渲染，同时即使在不施加任何时间固定的正则化合物的情况下保持较高的图像质量和时间连贯性。

We present a method that synthesizes novel views of complex scenes by interpolating a sparse set of nearby views. The core of our method is a network architecture that includes a multilayer perceptron and a ray transformer that estimates radiance and volume density at continuous 5D locations (3D spatial locations and 2D viewing directions), drawing appearance information on the fly from multiple source views. By drawing on source views at render time, our method hearkens back to classic work on image-based rendering (IBR), and allows us to render high-resolution imagery. Unlike neural scene representation work that optimizes per-scene functions for rendering, we learn a generic view interpolation function that generalizes to novel scenes. We render images using classic volume rendering, which is fully differentiable and allows us to train using only multiview posed images as supervision. Experiments show that our method outperforms recent novel view synthesis methods that also seek to generalize to novel scenes. Further, if fine-tuned on each scene, our method is competitive with state-of-the-art single-scene neural rendering methods. 1

NeRF synthesizes novel views of a scene with unprecedented quality by fitting a neural radiance field to RGB images. However, NeRF requires querying a deep Multi-Layer Perceptron (MLP) millions of times, leading to slow rendering times, even on modern GPUs. In this paper, we demonstrate that real-time rendering is possible by utilizing thousands of tiny MLPs instead of one single large MLP. In our setting, each individual MLP only needs to represent parts of the scene, thus smaller and faster-to-evaluate MLPs can be used. By combining this divide-and-conquer strategy with further optimizations, rendering is accelerated by three orders of magnitude compared to the original NeRF model without incurring high storage costs. Further, using teacher-student distillation for training, we show that this speed-up can be achieved without sacrificing visual quality.

Photo-realistic free-viewpoint rendering of real-world scenes using classical computer graphics techniques is challenging, because it requires the difficult step of capturing detailed appearance and geometry models. Recent studies have demonstrated promising results by learning scene representations that implicitly encode both geometry and appearance without 3D supervision. However, existing approaches in practice often show blurry renderings caused by the limited network capacity or the difficulty in finding accurate intersections of camera rays with the scene geometry. Synthesizing high-resolution imagery from these representations often requires time-consuming optical ray marching. In this work, we introduce Neural Sparse Voxel Fields (NSVF), a new neural scene representation for fast and high-quality free-viewpoint rendering. NSVF defines a set of voxel-bounded implicit fields organized in a sparse voxel octree to model local properties in each cell. We progressively learn the underlying voxel structures with a diffentiable ray-marching operation from only a set of posed RGB images. With the sparse voxel octree structure, rendering novel views can be accelerated by skipping the voxels containing no relevant scene content. Our method is typically over 10 times faster than the state-of-the-art (namely, NeRF (Mildenhall et al., 2020)) at inference time while achieving higher quality results. Furthermore, by utilizing an explicit sparse voxel representation, our method can easily be applied to scene editing and scene composition. We also demonstrate several challenging tasks, including multi-scene learning, free-viewpoint rendering of a moving human, and large-scale scene rendering. Code and data are available at our website: https://github.com/facebookresearch/NSVF.

关于神经辐射场（NERF）的最新研究爆炸表明，具有神经网络的复杂场面具有令人鼓舞的潜力。 NERF的一个主要缺点是它的推理时间：渲染单像素需要数百次查询NERF网络。为了解决它，现有的努力主要试图减少所需的采样点的数量。但是，迭代采样的问题仍然存在。另一方面，神经光场（NELF）在新型视图合成中对NERF提出了更直接的表示 - 像素的渲染相当于一个单一的正向通行，而无需射线建设。在这项工作中，我们提出了一个深层残留的MLP网络（88层），以有效地学习光场。我们展示了成功学习这种深度NELF网络的关键，就是拥有足够的数据，我们通过数据蒸馏从预训练的NERF模型中转移知识。在合成和现实世界场景上进行的广泛实验表明，我们方法比其他对应算法的优点。在合成场景中，我们实现了26-35倍的拖鞋（每个摄像头射线）和28-31倍的运行时加速，同时提供了比NERF的呈现质量（1.4-2.8 dB的平均PSNR改善），而无需任何定制的并行性要求。

我们引入了一个可扩展的框架，用于从RGB-D图像中具有很大不完整的场景覆盖率的新型视图合成。尽管生成的神经方法在2D图像上表现出了惊人的结果，但它们尚未达到相似的影像学结果，并结合了场景完成，在这种情况下，空间3D场景的理解是必不可少的。为此，我们提出了一条在基于网格的神经场景表示上执行的生成管道，通过以2.5D-3D-2.5D方式进行场景的分布来完成未观察到的场景部分。我们在3D空间中处理编码的图像特征，并具有几何完整网络和随后的纹理镶嵌网络，以推断缺失区域。最终可以通过与一致性的可区分渲染获得感性图像序列。全面的实验表明，我们方法的图形输出优于最新技术，尤其是在未观察到的场景部分中。

我们呈现Geonerf，一种基于神经辐射场的完全光电素质性新颖性研究综合方法。我们的方法由两个主要阶段组成：几何推理和渲染器。为了渲染新颖的视图，几何件推理首先为每个附近的源视图构造级联成本卷。然后，使用基于变压器的注意力机制和级联成本卷，渲染器Infers的几何和外观，并通过经典音量渲染技术呈现细节的图像。特别是该架构允许复杂的遮挡推理，从一致的源视图中收集信息。此外，我们的方法可以在单个场景中轻松进行微调，通过每场比较优化的神经渲染方法呈现竞争结果，其数量是计算成本。实验表明，Geonerf优于各种合成和实时数据集的最先进的最新神经渲染模型。最后，随着对几何推理的略微修改，我们还提出了一种适应RGBD图像的替代模型。由于深度传感器，该模型通常直接利用经常使用的深度信息。实施代码将公开可用。

我们呈现高动态范围神经辐射字段（HDR-NERF），以从一组低动态范围（LDR）视图的HDR辐射率字段与不同的曝光。使用HDR-NERF，我们能够在不同的曝光下生成新的HDR视图和新型LDR视图。我们方法的关键是模拟物理成像过程，该过程决定了场景点的辐射与具有两个隐式功能的LDR图像中的像素值转换为：RADIACE字段和音调映射器。辐射场对场景辐射（值在0到+末端之间的值变化），其通过提供相应的射线源和光线方向来输出光线的密度和辐射。 TONE MAPPER模拟映射过程，即在相机传感器上击中的光线变为像素值。通过将辐射和相应的曝光时间送入音调映射器来预测光线的颜色。我们使用经典的卷渲染技术将输出辐射，颜色和密度投影为HDR和LDR图像，同时只使用输入的LDR图像作为监控。我们收集了一个新的前瞻性的HDR数据集，以评估所提出的方法。综合性和现实世界场景的实验结果验证了我们的方法不仅可以准确控制合成视图的曝光，还可以用高动态范围呈现视图。