We propose PFAvatar (Pose-Fusion Avatar), a new method that reconstructs high-quality 3D avatars from Outfit of the Day (OOTD) photos, which exhibit diverse poses, occlusions, and complex backgrounds. Our method consists of two stages: (1) fine-tuning a pose-aware diffusion model from few-shot OOTD examples and (2) distilling a 3D avatar represented by a neural radiance field (NeRF). In the first stage, unlike previous methods that segment images into assets (e.g. garments, accessories) for 3D assembly, which is prone to inconsistency, we avoid decomposition and directly model the full-body appearance. By integrating a pre-trained ControlNet for pose estimation and a novel Condition Prior Preservation Loss (CPPL), our method enables end-to-end learning of fine details while mitigating language drift in few-shot training. Our method completes personalization in just 5 minutes, achieving a 48x speed-up compared to previous approaches. In the second stage, we introduce a NeRF-based avatar representation optimized by canonical SMPL-X space sampling and Multi-Resolution 3D-SDS. Compared to mesh-based representations that suffer from resolution-dependent discretization and erroneous occluded geometry, our continuous radiance field can preserve high-frequency textures (e.g., hair) and handle occlusions correctly through transmittance. Experiments demonstrate that PFAvatar outperforms state-of-the-art methods in terms of reconstruction fidelity, detail preservation, and robustness to occlusions/truncations, advancing practical 3D avatar generation from real-world OOTD albums. In addition, the reconstructed 3D avatars support downstream applications such as virtual try-on, animation, and human video reenactment, further demonstrating the versatility and practical value of our approach.

In this paper, we propose a novel framework for controllable video diffusion, OmniVDiff , aiming to synthesize and comprehend multiple video visual content in a single diffusion model. To achieve this, OmniVDiff treats all video visual modalities in the color space to learn a joint distribution, while employing an adaptive control strategy that dynamically adjusts the role of each visual modality during the diffusion process, either as a generation modality or a conditioning modality. Our framework supports three key capabilities: (1) Text-conditioned video generation, where all modalities are jointly synthesized from a textual prompt; (2) Video understanding, where structural modalities are predicted from rgb inputs in a coherent manner; and (3) X-conditioned video generation, where video synthesis is guided by finegrained inputs such as depth, canny and segmentation. Extensive experiments demonstrate that OmniVDiff achieves state-of-the-art performance in video generation tasks and competitive results in video understanding. Its flexibility and scalability make it well-suited for downstream applications such as video-to-video translation, modality adaptation for visual tasks, and scene reconstruction.

Recently, generating 3D assets with the control of condition images has achieved impressive quality. However, existing 3D generation methods are limited to handling a single control objective and lack the ability to utilize multiple images to independently control different regions of a 3D asset, which hinders their flexibility in applications. We propose Fuse3D, a novel method that enables generating 3D assets under the control of multiple images, allowing for the seamless fusion of multi-level regional controls from global views to intricate local details. First, we introduce a Multi-Condition Fusion Module to integrate the visual features from multiple image regions. Then, we propose a method to automatically align user-selected 2D image regions with their associated 3D regions based on semantic cues. Finally, to resolve control conflicts and enhance local control features from multi-condition images, we introduce a Local Attention Enhancement Strategy that flexibly balances region-specific feature fusion. Overall, we introduce the first method capable of controllable 3D asset generation from multiple condition images. The experimental results indicate that Fuse3D can flexibly fuse multiple 2D image regions into coherent 3D structures, resulting in high-quality 3D assets. Code and data for this paper are at https://jinnmnm.github.io/Fuse3d.github.io/.

Recent advances in neural rendering have mainly focused on modeling radiance fields with neural representations, often overlooking the underlying mechanisms for producing various lighting effects, and consequently leading to the limited adaptability to dynamic scenes. Lighting effects, such as highlights, shadows, and indirect illuminations, are typically computed using physically-based rendering methods like path tracing, which can be computationally intensive for complex indoor luminaires. Although several recent studies have aimed to model global illumination effects with neural representations, they commonly suffer from long training times or poor generalizability to new scenes. Addressing these challenges, this work presents a novel neural lighting function generation model capable of synthesizing diverse lighting effects in real time for unseen dynamic scenes and complex indoor luminaires, achieving results comparable to state-of-the-art rendering pipelines. Our model operates in two stages. First, multi-view observation images of the luminaire are captured to encode a compact, scene-independent 3D neural lighting field. Subsequently, light information is sampled from this neural lighting field and integrated with G-buffers and shadow clues to produce the shading results. In parallel, we employ a state-of-the-art generative model together with our training-free Inverse HDR Splatting module to generate HDR 3D Gaussians representing the luminaire. This strategy capitalizes on the powerful generalization capabilities of advanced generative models, enabling efficient and accurate appearance reconstruction for a diverse range of complex luminaires. In our experiments, the model trained on a dataset of 10,000 modern indoor scenes and thousands of illuminations demonstrates strong generalizability, high efficiency, and visually convincing results across a wide range of test scenes, highlighting its potential as a practical and flexible solution for high-fidelity, real-time neural indoor rendering.

High-quality Physically-Based Rendering (PBR) materials are crucial for visual realism in 3D asset creation, yet existing methods primarily target static objects, leading to challenges in maintaining multi-frame consistency for animatable entities. To tackle this issue, we introduce AniTex, the first generative pipeline that utilizes diffusion models to synthesize high-quality PBR materials for animatable objects based on text prompts. The pipeline consists of three key stages: First, sequences of RGB images are generated using a video diffusion model conditioned on depth, normals, irradiance, and motion vectors to ensure temporal coherence and geometric alignment across multiple frames and viewpoints. Second, these RGB image sequences are decomposed into per-view, per-frame PBR material maps (albedo, roughness, metallic) by a specialized Intrinsic Diffusion Model (IDM), which is conditioned on the RGB images along with consistent geometry and lighting cues to disentangle material from illumination. Finally, these per-view, per-frame PBR maps are hierarchically blended. This process first ensures temporal coherence within each view’s frame sequence, then amalgamates these into globally consistent PBR materials for the animatable object, maintaining overall temporal coherence and visual consistency throughout its animation. Extensive experiments show that AniTex produces more realistic PBR materials for both static and animated objects, outperforming baseline methods in visual appeal.

In recent years, the community has seen the emergence of neural-based super-resolution and frame generation techniques. These methods have effectively sped up high-resolution rendering by exploiting the spatial and temporal coherence between sequential frames, but none of them are designed specifically for improving the rendering performance in VR applications, where stereo rendering doubles the rendering cost.

Advances in mobile cameras have made it easier to capture ultra-high resolution (UHR) portraits. However, existing face reconstruction methods lack specific adaptations for UHR input (e.g., 4096 × 4096), leading to under-use of high-frequency details that are crucial for achieving photorealistic rendering. Our method supports 4096 × 4096 UHR input and utilizes a divide-and-conquer approach for end-to-end 4K albedo, micronormal, and specular texture reconstruction at the original resolution. We employ a two-stage strategy to capture both global distributions and local high-frequency details, effectively mitigating mosaic and seam artifacts common in patch-based prediction. Additionally, we innovatively apply hash encoding to facial U-V coordinates to boost the model’s ability to learn regional high-frequency feature distributions. Our method can be easily incorporated in state-of-the-art facial geometry reconstruction pipelines, significantly improving the texture reconstruction quality, facilitating artistic creation workflows.

Realistic human skin rendering has been a long-standing challenge in computer graphics. Recently, biophysical-based skin rendering has received increasing attention, as it provides a more realistic skin-rendering and a more intuitive way to adjust the skin style. In this work, we present a novel heterogeneous biophysical-based volume rendering method for human skin that improves the realism of skin appearance while easily simulating various types of skin effects, including skin diseases, by modifying biological coefficient textures. Specifically, we introduce a two-layer skin representation by mesh deformation that explicitly models the epidermis and dermis with heterogeneous volumetric medium layers containing the corresponding spatially varying melanin and hemoglobin, respectively. Furthermore, to better facilitate skin acquisition, we introduced a learning-based framework that automatically estimates spatially varying biological coefficients from an albedo texture, enabling biophysical-based and intuitive editing, such as tanning, pathological vitiligo, and freckles. We illustrated the effects of multiple skin-editing applications and demonstrated superior quality to the commonly used random walk skin-rendering method, with more convincing skin details regarding subsurface scattering.

Recent advances in cloud rendering have brought us a promising alternative for interactive photorealistic rendering on lightweight devices, which used to be only available on high-end platforms equipped with powerful graphic cards. This technique enables users to perform rendering-related creative tasks, such as 3D product visualization and lighting design, from the comfort of any location using handheld devices, rather than being confined to the front of a noisy heat-generating workstation. However, existing large-scale cloud rendering systems that stream path-traced frames from the server to the client present extremely high rendering costs and transmission bandwidth requirements, even with advanced path-tracing acceleration and video compression techniques. To alleviate these problems, we propose a novel streaming-aware rendering framework that is able to learn a joint optimal model integrating two path-tracing acceleration techniques (adaptive sampling and denoising) and video compression technique. Our joint model can fully exploit the inherent connections between these techniques and thus achieve substantially reduced rendering costs and enhanced compression quality. We also introduce the collaboration of client rendering ability to assist the frame decoding by rendering G-buffers as the shared side information. We demonstrate that appropriately incorporating the geometry and material priors from G-buffers into a neural compression pipeline can significantly reduce the streaming bandwidth in a cloud rendering system, and lighten the compression module design for computation efficiency. Our experiments show that our method delivers the best quality at various bitrates compared to existing Monte Carlo rendering streaming schemes, while remaining lightweight and efficient for cross-platform thin clients, including mobiles and tablets.

Heterogeneous surfaces exhibit spatially varying geometry and material, and therefore admit diverse appearances. Existing computer graphics works can only model heterogeneity using explicit structures or statistical parameters that describe a coarser level of detail. We extend the boundary by introducing a new model that describes the heterogeneous surfaces fully statistically at the microscopic level, with rich geometry and material details that are comparable to the wavelengths of light. We treat the heterogeneous surfaces as a mixture of stochastic vector processes. We adapt the well-known generalized Harvey-Shack theory to quantify the mean scattered intensity, i.e., the BRDF of these surfaces. We further explore the covariance statistic of the scattered field and derive its rank-1 decomposition. This leads to a practical algorithm that samples the speckles (fluctuating intensities) from the statistics, enriching the appearance without explicit definition of heterogeneous surfaces. The formulations are analytic, and we validate the quantities by comprehensive numerical simulations. Our heterogeneous surface model demonstrates various applications including corrosion (natural), particle deposition (man-made), and height-correlated mixture (artistic). Code for this paper is available at https://github.com/Rendering-at-ZJU/HeteroSurface.

The demand for high-frame-rate rendering keeps increasing in modern displays. Existing frame generation and super-resolution techniques accelerate rendering by reducing rendering samples across space or time. However, they rely on a uniform sampling reduction strategy, which undersamples areas with complex details or dynamic shading. To address this, we propose to sparsely shade critical areas while reusing generated pixels in low-variation areas for neural extrapolation. Specifically, we introduce the Predictive Error-Flow-eXtrapolation Network (EFXNet)-an architecture that predicts extrapolation errors, estimates flows, and extrapolates frames at once. Firstly, EFXNet leverages temporal coherence to predict extrapolation error and guide the sparse shading of dynamic areas. In addition, EFXNet employs a target-grid correlation module to estimate robust optical flows from pixel correlations rather than pixel values. Finally, EFXNet uses dedicated motion representations for the historical geometric and lighting components, respectively, to extrapolate temporally stable frames. Extensive experimental results show that, compared with state-of-the-art methods, our frame extrapolation method exhibits superior visual quality and temporal stability under a low rendering budget.

Rendering realistic images in real-time on high-frame-rate display devices poses considerable challenges, even with advanced graphics cards. This stimulates a demand for frame prediction technologies to boost frame rates. The key to these algorithms is to exploit spatiotemporal coherence by warping rendered pixels with motion representations. However, existing motion estimation methods can suffer from low precision, high overhead, and incomplete support for visual effects. In this article, we present a rendered frame prediction framework with a novel motion representation, dubbed motion-guided flow (MoFlow) , aiming at overcoming the intrinsic limitations of optical flow and motion vectors and precisely capture the dynamics of intricate geometries, lighting, and translucent objects. Notably, we construct MoFlows using a recurrent feature streaming network, which specializes in learning latent motion features from multiple frames. The results of extensive experiments demonstrate that, compared to state-of-the-art methods, our method achieves superior visual quality and temporal stability with lower latency. The recurrent mechanism allows our method to predict single or multiple consecutive frames, increasing the frame rate by over 2×. The proposed approach represents a flexible pipeline to meet the demands of various graphics applications, devices, and scenarios.

Abstract The real world consists of mass phenomena, such as iridescence on thin film and metal oxide layers, that is only explicable by wave optics. Existing research can reproduce such effects with simple point lights or low‐frequency environmental lighting. However, it remains a difficult task to efficiently rendering these effects when near‐field, high‐frequency area lights are involved. This paper presents a high‐fidelity, real‐time rendering algorithm for the iridescence effect under polygonal lights. We introduce a novel set of spherical functions, Monomial‐Gaussians, to accurately fit iridescent materials' reflectance. With a precomputed lookup table, the Monomial‐Gaussians are easily integrated over spherical polygons in linear time. Importance sampling of Monomial‐Gaussians is also supported to efficiently reduce Monte‐Carlo error. Our approach produces accurate renderings of the iridescence effect while still preserving high frame rates.

Gradient-domain rendering estimates finite difference gradients of image intensities and reconstructs the final result by solving a screened Poisson problem, which shows improvements over merely sampling pixel intensities. Adaptive sampling is another orthogonal research area that focuses on distributing samples adaptively in the primal domain. However, adaptive sampling in the gradient domain with low sampling budget has been less explored. Our idea is based on the observation that signals in the gradient domain are sparse, which provides more flexibility for adaptive sampling. We propose a deep-learning-based end-to-end sampling and reconstruction framework in gradient-domain rendering, enabling adaptive sampling gradient and the primal maps simultaneously. We conducted extensive experiments for evaluation and showed that our method produces better reconstruction quality than other methods in the test dataset.

The generation of global illumination in real time has been a long-standing challenge in the graphics community, particularly in dynamic scenes with complex illumination. Recent neural rendering techniques have shown great promise by utilizing neural networks to represent the illumination of scenes and then decoding the final radiance. However, incorporating object parameters into the representation may limit their effectiveness in handling fully dynamic scenes. This work presents a neural rendering approach, dubbed LightFormer , that can generate realistic global illumination for fully dynamic scenes, including dynamic lighting, materials, cameras, and animated objects, in real time. Inspired by classic many-lights methods, the proposed approach focuses on the neural representation of light sources in the scene rather than the entire scene, leading to the overall better generalizability. The neural prediction is achieved by leveraging the virtual point lights and shading clues for each light. Specifically, two stages are explored. In the light encoding stage, each light generates a set of virtual point lights in the scene, which are then encoded into an implicit neural light representation, along with screen-space shading clues like visibility. In the light gathering stage, a pixel-light attention mechanism composites all light representations for each shading point. Given the geometry and material representation, in tandem with the composed light representations of all lights, a lightweight neural network predicts the final radiance. Experimental results demonstrate that the proposed LightFormer can yield reasonable and realistic global illumination in fully dynamic scenes with real-time performance.

In this work, we present I2-SDF, a new method for intrinsic indoor scene reconstruction and editing using differentiable Monte Carlo raytracing on neural signed distance fields (SDFs). Our holistic neural SDF-based frame-work jointly recovers the underlying shapes, incident radiance and materials from multi-view images. We introduce a novel bubble loss for fine-grained small objects and error-guided adaptive sampling scheme to largely improve the reconstruction quality on large-scale indoor scenes. Further, we propose to decompose the neural radiance field into spatially-varying material of the scene as a neural field through surface-based, differentiable Monte Carlo raytracing and emitter semantic segmentations, which enables physically based and photorealistic scene relighting and editing applications. Through a number of qualitative and quantitative experiments, we demonstrate the superior quality of our method on indoor scene reconstruction, novel view synthesis, and scene editing compared to state-of-the-art baselines. Our project page is at https://jingsenzhu.github.io/i2-sdf.

The utilization of dedicated ray tracing graphics cards has revolutionized the production of stunning visual effects in real-time rendering. However, the demand for high frame rates and high resolutions remains a challenge. The pixel warping approach is a crucial technique for increasing frame rate and resolution by exploiting the spatio-temporal coherence. To this end, existing super-resolution and frame prediction methods rely heavily on motion vectors from rendering engine pipelines to track object movements. This work builds upon state-of-the-art heuristic approaches by exploring a novel adaptive recurrent frame prediction framework that integrates learnable motion vectors. Our framework supports the prediction of transparency, particles, and texture animations, with improved motion vectors that capture shading, reflections, and occlusions, in addition to geometry movements. In addition, we introduce a feature streaming neural network, dubbed FSNet, that allows for the adaptive prediction of one or multiple sequential frames. Extensive experiments against state-of-the-art methods demonstrate that FSNet can operate at lower latency with significant visual enhancements and can upscale frame rates by at least two times. This approach offers a flexible pipeline to improve the rendering frame rates of various graphics applications and devices.

The workload of real-time rendering is steeply increasing as the demand for high resolution, high refresh rates, and high realism rises, overwhelming most graphics cards. To mitigate this problem, one of the most popular solutions is to render images at a low resolution to reduce rendering overhead, and then manage to accurately upsample the low-resolution rendered image to the target resolution, a.k.a. super-resolution techniques. Most existing methods focus on exploiting information from low-resolution inputs, such as historical frames. The absence of high frequency details in those LR inputs makes them hard to recover fine details in their high-resolution predictions. In this paper, we propose an efficient and effective super-resolution method that predicts high-quality upsampled reconstructions utilizing low-cost high-resolution auxiliary G-Buffers as additional input. With LR images and HR G-buffers as input, the network requires to align and fuse features at multi resolution levels. We introduce an efficient and effective H-Net architecture to solve this problem and significantly reduce rendering overhead without noticeable quality deterioration. Experiments show that our method is able to produce temporally consistent reconstructions in 4 × 4 and even challenging 8 × 8 upsampling cases at 4K resolution with real-time performance, with substantially improved quality and significant performance boost compared to existing works.Project page: https://isaac-paradox.github.io/FuseSR/

As the demand for high quality and high resolution in real-time rendering grows, superresolution is on its way to becoming a necessary component in modern real-time rendering applications (e.g., video games). The superresolution technique allows graphic applications to save computational costs by rendering at a lower resolution and reconstructing a high-resolution result. Nvidia introduced DLSS to the market as the first superresolution application in 2020, and NSRR was published on Siggraph the same year. Each of these approaches has shown powerful capabilities and is well suited to the needs of the industrial sector. In this paper, the authors propose the optimization potential of superresolution algorithms by introducing feature enhancement and feature caching modules and attempt to improve the current algorithms.

Conventionally, interior lighting design is technically complex yet challenging and requires professional knowledge and aesthetic disciplines of designers. This article presents a new digital lighting design framework for virtual interior scenes, which allows novice users to automatically obtain lighting layouts and interior rendering images with visually pleasing lighting effects. The proposed framework utilizes neural networks to retrieve and learn underlying design guidelines and the principles beneath the existing lighting designs, e.g., a newly constructed dataset of 6k 3D interior scenes from professional designers with dense annotations of lights. With a 3D furniture-populated indoor scene as the input, the framework takes two stages to perform lighting design: (1) lights are iteratively placed in the room; (2) the colors and intensities of the lights are optimized by an adversarial scheme, resulting in lighting designs with aesthetic lighting effects. Quantitative and qualitative experiments show that the proposed framework effectively learns the guidelines and principles and generates lighting designs that are preferred over the rule-based baseline and comparable to those of professional human designers.

This article presents object-oriented neural light transfer (NeLT), a novel neural representation of the dynamic light transportation between an object and the environment. Our method disentangles the global illumination of a scene into individual objects’ light transportation represented via neural networks, then composes them explicitly. It therefore enables flexible rendering with dynamic lighting, cameras, materials, and objects. Our rendering features various important global illumination effects, such as diffuse illumination, glossy illumination, dynamic shadowing, and indirect illumination, which completes the capability of existing neural object representation. Experiments show that NeLT does not require path tracing or shading results as input but achieves rendering quality comparable to state-of-the-art rendering frameworks, including the recent deep learning based denoisers.

The level of detail (LOD) technique has been widely exploited as a key rendering optimization in many graphics applications. Numerous approaches have been proposed to automatically generate different kinds of LODs, such as geometric LOD or shader LOD. However, none of them have considered simplifying the geometry and shader at the same time. In this paper, we explore the observation that simplifications of geometric and shading details can be combined to provide a greater variety of tradeoffs between performance and quality. We present a new discrete multiresolution representation of objects, which consists of mesh and shader LODs. Each level of the representation could contain both simplified representations of shader and mesh. To create such LODs, we propose two automatic algorithms that pursue the best simplifications of meshes and shaders at adaptively selected distances. The results show that our mesh and shader LOD achieves better performance-quality tradeoffs than prior LOD representations, such as those that only consider simplified meshes or shaders.

Indoor scenes typically exhibit complex, spatially-varying appearance from global illumination, making inverse rendering a challenging ill-posed problem. This work presents an end-to-end, learning-based inverse rendering framework incorporating differentiable Monte Carlo raytracing with importance sampling. The framework takes a single image as input to jointly recover the underlying geometry, spatially-varying lighting, and photorealistic materials. Specifically, we introduce a physically-based differentiable rendering layer with screen-space ray tracing, resulting in more realistic specular reflections that match the input photo. In addition, we create a large-scale, photorealistic indoor scene dataset with significantly richer details like complex furniture and dedicated decorations. Further, we design a novel out-of-view lighting network with uncertainty-aware refinement leveraging hypernetwork-based neural radiance fields to predict lighting outside the view of the input photo. Through extensive evaluations on common benchmark datasets, we demonstrate superior inverse rendering quality of our method compared to state-of-the-art baselines, enabling various applications such as complex object insertion and material editing with high fidelity. Code and data will be made available at https://jingsenzhu.github.io/invrend

Abstract Evaluating shading functions on geometry surfaces dominates the rendering computation. A high‐quality but time‐consuming estimate is usually achieved with a dense sampling rate for pixels or sub‐pixels. In this paper, we leverage sparsely sampled points on vertices of dynamically‐generated subdivision surfaces to approximate the ground‐truth shading signal by piecewise linear reconstruction. To control the introduced interpolation error at runtime, we analytically derive an L∞ error bound and compute the optimal subdivision surfaces based on a user‐specified error threshold. We apply our analysis on multiple shading functions including Lambertian, Blinn‐Phong, Microfacet BRDF and also extend it to handle textures, yielding easy‐to‐compute formulas. To validate our derivation, we design a forward multirate shading algorithm powered by hardware tessellator that moves shading computation at pixels to the vertices of subdivision triangles on the fly. We show our approach significantly reduces the sampling rates on various test cases, reaching a speedup ratio of 134% ~ 283% compared to dense per‐pixel shading in current graphics hardware.

Abstract With the rapid development of data‐driven techniques, data has played an essential role in various computer vision tasks. Many realistic and synthetic datasets have been proposed to address different problems. However, there are lots of unresolved challenges: (1) the creation of dataset is usually a tedious process with manual annotations, (2) most datasets are only designed for a single specific task, (3) the modification or randomization of the 3D scene is difficult, and (4) the release of commercial 3D data may encounter copyright issue. This paper presents MINERVAS, a Massive INterior EnviRonments VirtuAl Synthesis system, to facilitate the 3D scene modification and the 2D image synthesis for various vision tasks. In particular, we design a programmable pipeline with Domain‐Specific Language, allowing users to select scenes from the commercial indoor scene database, synthesize scenes for different tasks with customized rules, and render various types of imagery data, such as color images, geometric structures, semantic labels. Our system eases the difficulty of customizing massive scenes for different tasks and relieves users from manipulating fine‐grained scene configurations by providing user‐controllable randomness using multilevel samplers. Most importantly, it empowers users to access commercial scene databases with millions of indoor scenes and protects the copyright of core data assets, e.g., 3D CAD models. We demonstrate the validity and flexibility of our system by using our synthesized data to improve the performance on different kinds of computer vision tasks. The project page is at https://coohom.github.io/MINERVAS .

In this article, we introduce a compact representation for measured BRDFs by leveraging Neural Processes (NPs). Unlike prior methods that express those BRDFs as discrete high-dimensional matrices or tensors, our technique considers measured BRDFs as continuous functions and works in corresponding function spaces . Specifically, provided the evaluations of a set of BRDFs, such as ones in MERL and EPFL datasets, our method learns a low-dimensional latent space as well as a few neural networks to encode and decode these measured BRDFs or new BRDFs into and from this space in a non-linear fashion. Leveraging this latent space and the flexibility offered by the NPs formulation, our encoded BRDFs are highly compact and offer a level of accuracy better than prior methods. We demonstrate the practical usefulness of our approach via two important applications, BRDF compression and editing. Additionally, we design two alternative post-trained decoders to, respectively, achieve better compression ratio for individual BRDFs and enable importance sampling of BRDFs.

With the prevalence of embedded GPUs on mobile devices, power-efficient rendering has become a widespread concern for graphics applications. Reducing the power consumption of rendering applications is critical for extending battery life. In this paper, we present a new real-time power-budget rendering system to meet this need by selecting the optimal rendering settings that maximize visual quality for each frame under a given power budget. Our method utilizes two independent neural networks trained entirely by synthesized datasets to predict power consumption and image quality under various workloads. This approach spares time-consuming precomputation or runtime periodic refitting and additional error computation. We evaluate the performance of the proposed framework on different platforms, two desktop PCs and two smartphones. Results show that compared to the previous state of the art, our system has less overhead and better flexibility. Existing rendering engines can integrate our system with negligible costs.

Most commercially available optical see-through head-mounted displays (OST-HMDs) utilize optical combiners to simultaneously visualize the physical background and virtual objects. The displayed images perceived by users are a blend of rendered pixels and background colors. Enabling high fidelity color perception in mixed reality (MR) scenarios using OST-HMDs is an important but challenging task. We propose a real-time rendering scheme to enhance the color contrast between virtual objects and the surrounding background for OST-HMDs. Inspired by the discovery of color perception in psychophysics, we first formulate the color contrast enhancement as a constrained optimization problem. We then design an end-to-end algorithm to search the optimal complementary shift in both chromaticity and luminance of the displayed color. This aims at enhancing the contrast between virtual objects and the real background as well as keeping the consistency with the original displayed color. We assess the performance of our approach using a simulated OST-HMD environment and an off-the-shelf OST-HMD. Experimental results from objective evaluations and subjective user studies demonstrate that the proposed approach makes rendered virtual objects more distinguishable from the surrounding background, thereby bringing a better visual experience.

Abstract Real‐time Monte Carlo denoising aims at removing severe noise under low samples per pixel (spp) in a strict time budget. Recently, kernel‐prediction methods use a neural network to predict each pixel's filtering kernel and have shown a great potential to remove Monte Carlo noise. However, the heavy computation overhead blocks these methods from real‐time applications. This paper expands the kernel‐prediction method and proposes a novel approach to denoise very low spp (e.g., 1‐spp) Monte Carlo path traced images at real‐time frame rates. Instead of using the neural network to directly predict the kernel map, i.e., the complete weights of each per‐pixel filtering kernel, we predict an encoding of the kernel map, followed by a high‐efficiency decoder with unfolding operations for a high‐quality reconstruction of the filtering kernels. The kernel map encoding yields a compact single‐channel representation of the kernel map, which can significantly reduce the kernel‐prediction network's throughput. In addition, we adopt a scalable kernel fusion module to improve denoising quality. The proposed approach preserves kernel prediction methods’ denoising quality while roughly halving its denoising time for 1‐spp noisy inputs. In addition, compared with the recent neural bilateral grid‐based real‐time denoiser, our approach benefits from the high parallelism of kernel‐based reconstruction and produces better denoising results at equal time.

Micro-appearance models offer state-of-the-art quality for cloth renderings. Unfortunately, they usually rely on 3D volumes or fiber meshes that are not only data-intensive but also expensive to render. Traditional surface-based models, on the other hand, are light-weight and fast to render but normally lack the fidelity and details important for design and prototyping applications. We introduce a multi-scale, hybrid model to bridge this gap for thin fabrics. Our model enjoys both the compactness and speedy rendering offered by traditional surface-based models and the rich details provided by the micro-appearance models. Further, we propose a new algorithm to convert state-of-the-art micro-appearance models into our representation while qualitatively preserving the detailed appearance. We demonstrate the effectiveness of our technique by integrating it into a real-time rendering system.

Abstract It is still challenging to render directional but non‐specular reflections in complex scenes. The SG‐based (Spherical Gaussian) many‐light framework provides a scalable solution but still requires a large number of glossy virtual lights to avoid spikes as well as reduce clamping errors. Directly gathering contributions from these glossy virtual lights to each pixel in a pairwise way is very inefficient. In this paper, we propose an adaptive algorithm with tighter error bounds to efficiently compute glossy interreflections from glossy virtual lights. This approach is an extension of the Lightcuts that builds hierarchies on both lights and pixels with new error bounds and new GPU‐based traversal methods between light and pixel hierarchies. Results demonstrate that our method is able to faithfully and efficiently compute glossy interreflections in scenes with highly glossy and spatial varying reflectance. Compared with the conventional Lightcuts method, our approach generates lightcuts with only one‐fourth to one‐fifth light nodes therefore exhibits better scalability. Additionally, after being implemented on GPU, our algorithms achieve a magnitude of faster performance than the previous method.

Abstract In this paper, we present a new shader smoothing method to improve the quality and generality of band‐limiting shader programs. Previous work [YB18] treats intermediate values in the program as random variables, and utilizes mean and variance statistics to smooth shader programs. In this work, we extend such a band‐limiting framework by exploring the observation that one intermediate value in the program is usually computed by a complex composition of functions, where the domain and range of composited functions heavily impact the statistics of smoothed programs. Accordingly, we propose three new shader smoothing rules for specific composition of functions by considering the domain and range, enabling better mean and variance statistics of approximations. Aside from continuous functions, the texture, such as color texture or normal map, is treated as a discrete function with limited domain and range, thereby can be processed similarly in the newly proposed framework. Experiments show that compared with previous work, our method is capable of generating better smoothness of shader programs as well as handling a broader set of shader programs.

Serious noise affects the rendering of global illumination using Monte Carlo (MC) path tracing when insufficient samples are used. The two common solutions to this problem are filtering noisy inputs to generate smooth but biased results and sampling the MC integrand with a carefully crafted probability distribution function (PDF) to produce unbiased results. Both solutions benefit from an efficient incident radiance field sampling and reconstruction algorithm. This study proposes a method for training quality and reconstruction networks (Q- and R-networks, respectively) with a massive offline dataset for the adaptive sampling and reconstruction of first-bounce incident radiance fields. The convolutional neural network (CNN)-based R-network reconstructs the incident radiance field in a 4D space, whereas the deep reinforcement learning (DRL)-based Q-network predicts and guides the adaptive sampling process. The approach is verified by comparing it with state-of-the-art unbiased path guiding methods and filtering methods. Results demonstrate improvements for unbiased path guiding and competitive performance in biased applications, including filtering and irradiance caching.

This work proposes a new stereo shading architecture that enables adaptive shading rates and automatic shading reuse among triangles and between two views. The proposed pipeline presents several novel features. First, the present sort-middle/bin shading is extended to tile pair-based shading to rasterize and shade pixels at two views simultaneously. A new rasterization algorithm utilizing epipolar geometry is then proposed to schedule tile pairs and perform rasterization at stereo views efficiently. Second, this work presents an adaptive multi-rate shading framework to compute shading on pixels at different rates. A novel tile-based screen space cache and a new cache reuse shader are proposed to perform such multi-rate shading across triangles and views. The results show that the newly proposed method outperforms the standard sort-middle shading and the state-of-the-art multi-rate shading by achieving considerably lower shading cost and memory bandwidth.

Line drawing is an important and concise method to depict the shape of an object. Stereo line drawing, a combination of line drawing and stereo rendering, not only efficiently conveys shape but also provides users with a visual experience of a stereoscopic 3D world. Contours are the most important lines to draw. However, contours must be rendered consistently for two eyes because of their view-dependent nature; otherwise, they cause binocular rivalry and viewing discomfort. This paper proposes a novel solution to draw stereo-consistent contours in real time. First, we extend the concept of epipolar-slidability and derive a new criterion to check epipolar-slidability by the monotonicity of the trajectory of the viewpoints of contour points. Then, we design an algorithm to test the epipolar-slidability of contours by conducting an image space search rather than sampling multiple viewpoints. Results show that the proposed method has a much lower cost than that of previous works, therefore enables the real-time rendering and editing of stereo-consistent contours for users, such as changing camera viewpoints, editing object geometry, tweaking parameters to show contours with different details, etc.

Redirected walking allows users to walk naturally through a large immersive virtual environment while the physical space is limited. Previous studies have analyzed human sensitivity to redirected walking in a horizontal direction, but users also need to walk on slopes to change their height. In this work, we expand the vertical movement space by positioning users on virtual paths with slopes that are different from those of real paths. We conduct psychological experiments to explore human sensitivity to slope gains that describe the discrepancies between the slopes of paths in virtual and real environments. The investigation shows that humans can walk on virtual slopes that are higher or lower than the real position without detecting the slopes and establishes corresponding detection thresholds.

Denoising Monte Carlo rendering with a very low sample rate remains a major challenge in the photo-realistic rendering research. Many previous works, including regression-based and learning-based methods, have been explored to achieve better rendering quality with less computational cost. However, most of these methods rely on handcrafted optimization objectives, which lead to artifacts such as blurs and unfaithful details. In this paper, we present an adversarial approach for denoising Monte Carlo rendering. Our key insight is that generative adversarial networks can help denoiser networks to produce more realistic high-frequency details and global illumination by learning the distribution from a set of high-quality Monte Carlo path tracing images. We also adapt a novel feature modulation method to utilize auxiliary features better, including normal, albedo and depth. Compared to previous state-of-the-art methods, our approach produces a better reconstruction of the Monte Carlo integral from a few samples, performs more robustly at different sample rates, and takes only a second for megapixel images.

Abstract Traditional automatic shader simplification simplifies shaders in an offline process, which is typically carried out in a context‐oblivious manner or with the use of some example contexts, e.g., certain hardware platforms, scenes, and uniform parameters, etc. As a result, these pre‐simplified shaders may fail at adapting to runtime changes of the rendering context that were not considered in the simplification process. In this paper, we propose a new automatic shader simplification technique, which explores two key aspects of a runtime simplification framework: the optimization space and the instant search for optimal simplified shaders with runtime context. The proposed technique still requires a preprocess stage to process the original shader. However, instead of directly computing optimal simplified shaders, the proposed preprocess generates a reduced shader optimization space. In particular, two heuristic estimates of the quality and performance of simplified shaders are presented to group similar variants into representative ones, which serve as basic graph nodes of the simplification dependency graph (SDG), a new representation of the optimization space. At the runtime simplification stage, a parallel discrete optimization algorithm is employed to instantly search in the SDG for optimal simplified shaders. New data‐driven cost models are proposed to predict the runtime quality and performance of simplified shaders on the basis of data collected during runtime. Results show that the selected simplifications of complex shaders achieve 1.6 to 2.5 times speedup and still retain high rendering quality.

Abstract Power saving is a prevailing concern in desktop computers and, especially, in battery‐powered devices such as mobile phones. This is generating a growing demand for power‐aware graphics applications that can extend battery life, while preserving good quality. In this paper, we address this issue by presenting a real‐time power‐efficient rendering framework, able to dynamically select the rendering configuration with the best quality within a given power budget. Different from the current state of the art, our method does not require precomputation of the whole camera‐view space, nor Pareto curves to explore the vast power‐error space; as such, it can also handle dynamic scenes. Our algorithm is based on two key components: our novel power prediction model, and our runtime quality error estimation mechanism. These components allow us to search for the optimal rendering configuration at runtime, being transparent to the user. We demonstrate the performance of our framework on two different platforms: a desktop computer, and a mobile device. In both cases, we produce results close to the maximum quality, while achieving significant power savings.

Abstract We present a new technique to jointly MIP‐map BRDF and normal maps. Starting with generating an instant BRDF map, our technique builds its MIP‐mapped versions based on a highly efficient algorithm that interpolates von Mises‐Fisher (vMF) distributions. In our BRDF MIP‐maps, each pixel stores a vMF mixture approximating the average of all BRDF lobes from the finest level. Our method is capable of jointly MIP‐mapping BRDF and normal maps, even with high‐frequency variations, at real‐time while preserving high‐quality reflectance details. Further, it is very fast, easy to implement, and requires no precomputation.

With recent advances on mobile computing, power consumption has become a significant limiting constraint for many graphics applications. As a result, rendering on a power budget arises as an emerging demand. In this paper, we present a real-time, power-optimal rendering framework to address this problem, by finding the optimal rendering settings that minimize power consumption while maximizing visual quality. We first introduce a novel power-error, multi-objective cost space, and formally formulate power saving as an optimization problem. Then, we develop a two-step algorithm to efficiently explore the vast power-error space and leverage optimal Pareto frontiers at runtime. Finally, we show that our rendering framework can be generalized across different platforms, desktop PC or mobile device, by demonstrating its performance on our own OpenGL rendering framework, as well as the commercially available Unreal Engine.

Several scalable many-light rendering methods have been proposed recently for the efficient computation of global illumination. However, gathering contributions of virtual lights in participating media remains an inefficient and time-consuming task. In this paper, we present a novel sparse sampling and reconstruction method to accelerate the gathering step of the many-light rendering for participating media. Our technique explores the observation that the scattered lightings are usually locally coherent and of low rank even in heterogeneous media. In particular, we first introduce a matrix formation with light segments as columns and eye ray segments as rows, and formulate the gathering step into a matrix sampling and reconstruction problem. We then propose an adaptive matrix column sampling and completion algorithm to efficiently reconstruct the matrix by only sampling a small number of elements. Experimental results show that our approach greatly improves the performance, and obtains up to one order of magnitude speedup compared with other state-of-the-art methods of many-light rendering for participating media.

Glossy to glossy reflections are lights bounced between glossy surfaces. Such directional light transports are important for humans to perceive glossy materials, but difficult to simulate. This paper proposes a new method for rendering screen-space glossy to glossy reflections in realtime. We use spherical von Mises-Fisher (vMF) distributions to model glossy BRDFs at surfaces, and employ screen space directional occlusion (SSDO) rendering framework to trace indirect light transports bounced in the screen space. As our main contributions, we derive a new parameterization of vMF distribution so as to convert the non-linear fit of multiple vMF distributions into a linear sum in the new space. Then, we present a new linear filtering technique to build MIP-maps on glossy BRDFs, which allows us to create filtered radiance transfer functions at runtime, and efficiently estimate indirect glossy to glossy reflections. We demonstrate our method in a realtime application for rendering scenes with dynamic glossy objects. Compared with screen space directional occlusion, our approach only requires one extra texture and has a negligible overhead, 3% ∼ 6% loss at frame rate, but enables glossy to glossy reflections.

Instead of computing on a large number of virtual point lights (VPLs), scalable many-lights rendering methods effectively simulate various illumination effects only using hundreds or thousands of representative VPLs. However, gathering illuminations from these representative VPLs, especially computing the visibility, is still a tedious and time-consuming task. In this paper, we propose a new matrix sampling-and-recovery scheme to efficiently gather illuminations by only sampling a small number of visibilities between representative VPLs and surface points. Our approach is based on the observation that the lighting matrix used in manylights rendering is of low-rank, so that it is possible to sparsely sample a small number of entries, and then numerically complete the entire matrix. We propose a three-step algorithm to explore this observation. First, we design a new VPL clustering algorithm to slice the rows and group the columns of the full lighting matrix into a number of reduced matrices, which are sampled and recovered individually. Second, we propose a novel prediction method that predicts visibility of matrix entries from sparsely and randomly sampled entries. Finally, we adapt the matrix separation technique to recover the entire reduced matrix and compute final shadings. Experimental results show that our method heavily reduces the required visibility sampling in the final gathering and achieves 3--7 times speedup compared with the state-of-the-art methods on test scenes.

As the 3D printing technology starts to revolutionize our daily life and the manufacturing industries, a critical problem is about to e-merge: how can we find an automatic way to divide a 3D model into multiple printable pieces, so as to save the space, to reduce the printing time, or to make a large model printable by small printers. In this paper, we present a systematic study on the partitioning and packing of 3D models under the multi-phase level set framework. We first construct analysis tools to evaluate the qualities of a partitioning using six metrics: stress load, surface details, interface area, packed size, printability, and assembling. Based on this analysis, we then formulate level set methods to improve the qualities of the partitioning according to the metrics. These methods are integrated into an automatic system, which repetitively and locally optimizes the partitioning. Given the optimized partitioning result, we further provide a container structure modeling algorithm to facilitate the packing process of the printed pieces. Our experiment shows that the system can generate quality partitioning of various 3D models for space saving and fast production purposes.

Abstract Modelling trees according to desired shapes is important for many applications. Despite numerous methods having been proposed in tree modelling, it is still a non‐trivial task and challenging. In this paper, we present a new variational computing approach for generating realistic trees in specific shapes. Instead of directly modelling trees from symbolic rules, we formulate the tree modelling as an optimization process, in which a variational cost function is iteratively minimized. This cost function measures the difference between the guidance shape and the target tree crown. In addition, to faithfully capture the branch structure of trees, several botanical factors, including the minimum total branches volume and spatial branches patterns, are considered in the optimization to guide the tree modelling process. We demonstrate that our approach is applicable to generate trees with different shapes, from interactive design and complex polygonal meshes.

Underwater scene is one of the most marvelous environments in the world. In this study, we present an efficient procedural modeling and rendering system to generate marine ecosystems for swim-through graphic applications. To produce realistic and natural underwater scenes, several techniques and algorithms have been presented and introduced. First, to distribute sealife naturally on a seabed, we employ an ecosystem simulation that considers the influence of the underwater environment. Second, we propose a two-level procedural modeling system to generate sealife with unique biological features. At the base level, a series of grammars are designed to roughly represent underwater sealife on a central processing unit (CPU). Then at the fine level, additional details of the sealife are created and rendered using graphic processing units (GPUs). Such a hybrid CPU-GPU framework best adopts sequential and parallel computation in modeling a marine ecosystem, and achieves a high level of performance. Third, the proposed system integrates dynamic simulations in the proposed procedural modeling process to support dynamic interactions between sealife and the underwater environment, where interactions and physical factors of the environment are formulated into parameters and control the geometric generation at the fine level. Results demonstrate that this system is capable of generating and rendering scenes with massive corals and sealife in real time.

In this paper, we present a new automatic shader simplification method using surface signal approximation. We regard the entire multi-stage rendering pipeline as a process that generates signals on surfaces, and we formulate the simplification of the fragment shader as a global simplification problem across multi-shader stages. Three new shader simplification rules are proposed to solve the problem. First, the code transformation rule transforms fragment shader code to other shader stages in order to redistribute computations on pixels up to the level of geometry primitives. Second, the surface-wise approximation rule uses high-order polynomial basis functions on surfaces to approximate pixel-wise computations in the fragment shader. These approximations are pre-cached and simplify computations at runtime. Third, the surface subdivision rule tessellates surfaces into smaller patches. It combines with the previous two rules to approximate pixel-wise signals at different levels of tessellations with different computation times and visual errors. To evaluate simplified shaders using these simplification rules, we introduce a new cost model that includes the visual quality, rendering time and memory consumption. With these simplification rules and the cost model, we present an integrated shader simplification algorithm that is capable of automatically generating variants of simplified shaders and selecting a sequence of preferable shaders. Results show that the sequence of selected simplified shaders balance performance, accuracy and memory consumption well.

In this paper, we present a GPU-based out-of-core rendering approach under the many-lights rendering framework. Many-lights rendering is an efficient and scalable rendering framework for a large number of lights. But when the data sizes of lights and geometry are both beyond the in-core memory storage size, the data management of these two out-of-core data becomes critical and challenging. In our approach, we formulate such a data management as a graph traversal optimization problem that first builds out-of-core lights and geometry data into a graph, and then guides shading computations by finding a shortest path to visit all vertices in the graph. Based on the proposed data management, we develop a GPU-based out-of-GPU-core rendering algorithm that manages data between the CPU host memory and the GPU device memory. Two main steps are taken in the algorithm: the out-of-core data preparation to pack data into optimal data layouts for the many-lights rendering, and the out-of-core shading using graph-based data management. We demonstrate our algorithm on scenes with out-of-core detailed geometry and out-of-core lights. Results show that our approach generates complex global illumination effects with increased data access coherence and has one order of magnitude performance gain over the CPU-based approach.

This paper presents a new technique for real-time relighting of static scenes with all-frequency shadows from complex lighting and highly specular reflections from spatially varying BRDFs. The key idea is to depict the boundaries of visible regions using piecewise linear functions, and convert the shading computation into double product integrals—the integral of the product of lighting and BRDF on visible regions. By representing lighting and BRDF with spherical Gaussians and approximating their product using Legendre polynomials locally in visible regions, we show that such double product integrals can be evaluated in an analytic form. Given the precomputed visibility, our technique computes the visibility boundaries on the fly at each shading point, and performs the analytic integral to evaluate the shading color. The result is a real-time all-frequency relighting technique for static scenes with dynamic, spatially varying BRDFs, which can generate more accurate shadows than the state-of-the-art real-time PRT methods.

Traditional gradient domain seamless image cloning is a time consuming task, requiring the solving of Poisson’s equations whenever the shape or position of the cloned region changes. Recently, a more efficient alternative, the mean-value coordinates (MVCs) based approach, was proposed to interpolate interior pixels by a weighted combination of values along the boundary. However, this approach cannot faithfully preserve the gradient in the cloning region. In this paper, we introduce harmonic cloning, which uses harmonic coordinates (HCs) instead of MVCs in image cloning. Benefiting from the non-negativity and interior locality of HCs, our interpolation generates a more accurate harmonic field across the cloned region, to preserve the results with as high a quality as with Poisson cloning. Furthermore, with optimizations and implementation on a graphic processing unit (GPU), we demonstrate that, compared with the method using MVCs, our harmonic cloning gains better quality while retaining real-time performance.

Abstract Solving aliasing artifacts is an essential problem in shadow mapping approaches. Many works have been proposed, however, most of them focused on removing the texel‐level aliasing that results from the limited resolution of shadow maps. Little work has been done to solve the pixel‐level shadow aliasing that is produced by the rasterization on the screen plane. In this paper, we propose a fast, sub‐pixel antialiased shadowing algorithm to solve the pixel aliasing problem. Our work is based on the alias‐free shadow maps, which is capable of computing accurate per‐pixel shadow, and only incurs little cost to extend to sub‐pixel accuracy. Instead of direct supersampling the screen space, we take facets to approximate pixels in shadow testing. The shadowed area of one facet is rapidly evaluated by projecting blocker geometry onto a supersampled 2D occlusion mask with bitmasks fusion. It provides a sub‐pixel occlusion sampling so as to capture fine shadow details and features. Furthermore, we introduce the silhouette mask map that limits visibility evaluation to pixels only on the silhouette, which greatly reduces the computation cost. Our algorithm runs entirely on the GPU, achieving real‐time performance and is an order of magnitude faster than the brute‐force supersampling method to produce comparable 32× antialiased shadows.

This paper presents a GPU-based method for interactive global illumination that integrates complex effects such as multi-bounce indirect lighting, glossy reflections, caustics, and arbitrary specular paths. Our method builds upon scattered data sampling and interpolation on the GPU. We start with raytraced shading points and partition them into coherent shading clusters using adaptive seeding followed by k-means. At each cluster center we apply final gather to evaluate its incident irradiance using GPU-based photon mapping. We approximate the entire photon tree as a compact illumination cut, thus reducing the final gather cost for each ray. The sampled irradiance values are then interpolated at all shading points to produce rendering. Our method exploits the spatial coherence of illumination to reduce sampling cost. We sample sparsely and the distribution of sample points conforms with the underlying illumination changes. Therefore our method is both fast and preserves high rendering quality. Although the same property has been exploited by previous caching and adaptive sampling methods, these methods typically require sequential computation of sample points, making them ill-suited for the GPU. In contrast, we select sample points adaptively in a single pass, enabling parallel computation. As a result, our algorithm runs entirely on the GPU, achieving interactive rates for scenes with complex illumination effects.

We present an algorithm for constructing kd-trees on GPUs. This algorithm achieves real-time performance by exploiting the GPU's streaming architecture at all stages of kd-tree construction. Unlike previous parallel kd-tree algorithms, our method builds tree nodes completely in BFS (breadth-first search) order. We also develop a special strategy for large nodes at upper tree levels so as to further exploit the fine-grained parallelism of GPUs. For these nodes, we parallelize the computation over all geometric primitives instead of nodes at each level. Finally, in order to maintain kd-tree quality, we introduce novel schemes for fast evaluation of node split costs. As far as we know, ours is the first real-time kd-tree algorithm on the GPU. The kd-trees built by our algorithm are of comparable quality as those constructed by off-line CPU algorithms. In terms of speed, our algorithm is significantly faster than well-optimized single-core CPU algorithms and competitive with multi-core CPU algorithms. Our algorithm provides a general way for handling dynamic scenes on the GPU. We demonstrate the potential of our algorithm in applications involving dynamic scenes, including GPU ray tracing, interactive photon mapping, and point cloud modeling.

Abstract In this paper, we introduce a new representation – radiance transfer fields (RTF) – for rendering interreflections in dynamic scenes under low frequency illumination. The RTF describes the radiance transferred by an individual object to its surrounding space as a function of the incident radiance. An important property of RTF is its independence of the scene configuration, enabling interreflection computation in dynamic scenes. Secondly, RTFs naturally fit in with the rendering framework of precomputed shadow fields, incurring negligible cost to add interreflection effects. In addition, RTFs can be used to compute interreflections for both diffuse and glossy objects. We also show that RTF data can be highly compressed by clustered principal component analysis (CPCA), which not only reduces the memory cost but also accelerates rendering. Finally, we present some experimental results demonstrating our techniques.

Previous methods for soft shadows numerically integrate over many light directions at each receiver point, testing blocker visibility in each direction. We introduce a method for real-time soft shadows in dynamic scenes illuminated by large, low-frequency light sources where such integration is impractical. Our method operates on vectors representing low-frequency visibility of blockers in the spherical harmonic basis. Blocking geometry is modeled as a set of spheres; relatively few spheres capture the low-frequency blocking effect of complicated geometry. At each receiver point, we compute the product of visibility vectors for these blocker spheres as seen from the point. Instead of computing an expensive SH product per blocker as in previous work, we perform inexpensive vector sums to accumulate the log of blocker visibility. SH exponentiation then yields the product visibility vector over all blockers. We show how the SH exponentiation required can be approximated accurately and efficiently for low-order SH, accelerating previous CPU-based methods by a factor of 10 or more, depending on blocker complexity, and allowing real-time GPU implementation.