Real-time Global Illumination Research Articles

Photon Field Networks for Dynamic Real-Time Volumetric Global Illumination.

Volume data is commonly found in many scientific disciplines, like medicine, physics, and biology. Experts rely on robust scientific visualization techniques to extract valuable insights from the data. Recent years have shown path tracing to be the preferred approach for volumetric rendering, given its high levels of realism. However, real-time volumetric path tracing often suffers from stochastic noise and long convergence times, limiting interactive exploration. In this paper, we present a novel method to enable real-time global illumination for volume data visualization. We develop Photon Field Networks-a phase-function-aware, multi-light neural representation of indirect volumetric global illumination. The fields are trained on multi-phase photon caches that we compute a priori. Training can be done within seconds, after which the fields can be used in various rendering tasks. To showcase their potential, we develop a custom neural path tracer, with which our photon fields achieve interactive framerates even on large datasets. We conduct in-depth evaluations of the method's performance, including visual quality, stochastic noise, inference and rendering speeds, and accuracy regarding illumination and phase function awareness. Results are compared to ray marching, path tracing and photon mapping. Our findings show that Photon Field Networks can faithfully represent indirect global illumination within the boundaries of the trained phase spectrum while exhibiting less stochastic noise and rendering at a significantly faster rate than traditional methods.

A Framework for Learning and Rapid Implementation of Real-Time Global Illumination Methods

Photorealism has become a growing requirement for real-time graphics applications. Among the components needed to obtain photorealism, one of the most important is the simulation of the light transport, the result of which is called global illumination. With the growing interest in the research in this field, the need to develop a learning approach for the methods that produce real-time global illumination and a technological basis have become important topics. In this paper, we present a framework for the rapid development and testing of such methods. The framework itself does not contain their implementations, but contains a set of components that underlie them. It has been developed with a multi-pass architecture that allows the reuse of pass implementations in several technique pipelines. Moreover, this framework can be used in the process of learning real-time global illumination methods thanks to an editor with graphical user interface (GUI) that offers a rich amount of information and a set of such methods, created in the framework for demonstration purposes. We evaluated the proposed framework in two ways. First, through a comparative analysis with other frameworks, which have been created or at least can be used for educational purposes and the rapid implementation of real-time global illumination techniques. The second evaluation was made for the applicability of the framework in learning by using it as software support in the process of testing global illumination knowledge on eight participants with background in computer graphics.

Clustered voxel real-time global illumination

Real-time global illumination is an extremely challenging problem because of its intrinsic complexity due to the interplay between complex geometry, multiple light bounces, and stringent real-time frame-rate requirements. In this paper, we present a new technique that enables the real-time computation of global illumination in generic scenes for diffuse surfaces and static geometry. Our technique combines a voxel-based representation of the scene, a voxel-clustering algorithm, and an iterative light-propagation algorithm based on the resulting clusters. Although our implementation is currently designed to handle the first (and main) bounce, the technique allows for multiple light bounces. Summing up all these components results in a flexible algorithm capable of providing global illumination effects and on-the-fly illumination computations.

Стан та перспективи подальших досліджень сфери обчислення глобального освітлення у реальному часі

Currently, computer graphics is a very important part of computer science. Graphics-related developments have been used in many different situations, for example, in animated and cinema movie productions, in computer graphics applications, modeling, and simulation systems, for different visualizations in medicine, mathematics, physics, etc. One of the main problems of computer graphics is the task of transforming the information of some imaginary scene and its observer into a photorealistic image of this scene for them. Solving this problem is very important, but right now obtaining a good quality result is possible only in a non-interactive scenario (for example, in animated films), while in real-time (for example, in computer modeling or simulations, in computer games) it is usually necessary to use some approximate algorithms. Although these algorithms are often able to provide a natural-looking result, they still have plenty of very noticeable inaccuracies. However, this topic is gaining more and more development recently due to the improvement of graphics processors. In addition to a significant increase in computation speed and the number of cores, the appearance of ray tracing hardware acceleration plays a large role. Global illumination computation is an inseparable part of photorealistic image generation. This paper is focused on solving this problem in real-time, which means developing a system capable of generating such images at a speed sufficient for the resulting sequence to be perceived by a person as a smooth animation. We give the theoretical information required for understanding this problem and describe existing methods and algorithms for solving it with their advantages and disadvantages. Also based on an overview of the topic's current state, we analyze further research prospects and directions for improving existing and developing new methods of real-time global illumination calculation, while considering compute power and technologies of the latest graphics hardware.

Comparative Analysis of Real-Time Global Illumination Techniques in Current Game Engines

The most important component of photorealism in Computer Graphics is given by a physically correct approximation of the light transport. Besides the direct illumination from light sources, there is an indirect illumination, produced by the reflections of the light rays on other surfaces of the scene. In Computer Graphics, the process of computing the illumination of a surface by considering both the direct and the indirect illumination is widely known as global illumination. This paper describes several classes of real-time global illumination techniques used in current game engines together with our own implementations of these approaches. All implementations were made in our own framework, specially designed with a multi-pass rendering architecture that allows fast implementation of rendering techniques and the reuse of functionalities. We analyze these classes based on the following criteria: the visual results produced by the indirect diffuse lighting, the ability to produce glossy reflections, shadows, ambient occlusion, subsurface scattering, translucency and volumetric lighting as well as the ability to simulate area lights. We present the quantitative results of our implementations, obtained with the same external parameters for all techniques, thanks to the unified implementations in the same framework. An important observation is that our analysis is focused on the techniques that are based on the rasterization pipeline, thus, the comparison does not include the techniques designed entirely for the ray-tracing pipeline.

On the Use of Deep Active Semi-Supervised Learning for Fast Rendering in Global Illumination

Convolution neural networks usually require large labeled data-sets to construct accurate models. However, in many real-world scenarios, such as global illumination, labeling data are a time-consuming and costly human intelligent task. Semi-supervised learning methods leverage this issue by making use of a small labeled data-set and a larger set of unlabeled data. In this paper, our contributions focus on the development of a robust algorithm that combines active and deep semi-supervised convolution neural network to reduce labeling workload and to accelerate convergence in case of real-time global illumination. While the theoretical concepts of photo-realistic rendering are well understood, the increased need for the delivery of highly dynamic interactive content in vast virtual environments has increased recently. Particularly, the quality measure of computer-generated images is of great importance. The experiments are conducted on global illumination scenes which contain diverse distortions. Compared with human psycho-visual thresholds, the good consistency between these thresholds and the learning models quality measures can been seen. A comparison has also been made with SVM and other state-of-the-art deep learning models. We do transfer learning by running the convolution base of these models over our image set. Then, we use the output features of the convolution base as input to retrain the parameters of the fully connected layer. The obtained results show that our proposed method provides promising efficiency in terms of precision, time complexity, and optimal architecture.

An adaptive rendering framework for efficient synthetic light field generation

Real-time global illumination rendering is very desirable for emerging applications such as Virtual Reality (VR) and Augmented Reality (AR). However, client devices have difficulties to support photo-realistic rendering, such as Ray-Tracing, due to insufficient computing resources. Many modern frameworks adopted Light Field rendering to support device displaying. A Light Field can be precomputed and stored in the Cloud. During runtime, the display extracts the color information from the Light Field to generate arbitrary real time viewpoints or re-focusing within a predefined area. To efficiently compute the Light Field, We have combined DIBR (Depth-Image-Based-Rendering) and traditional ray-tracing in an adaptive fashion to synthesize images. By measuring the color errors during runtime, we adaptively determine a good balance between DIBR and Ray Tracing. We study several cases and problems when combing these algorithms and came up with a more efficient solution. To further optimize the computation efficiency, we also added a multi-level design to exploit the degree of shareable pixels among images to control the computation for error reduction. In addition, we also design an efficient multi-threading scheduling to show the scalability of our approach. Experiments show that when the number of threads is small, we achieved up to 3.24X speedup in Light Field generation for relative simple scenes like Cornell Box, and about 2X speed up for complex scenes like Conference Room or Sponza. In the multi-thread environment, our proposed scheme can offer about 2X speedup over traditional ones.

Real-Time Rendering with Lighting Grid Hierarchy

We present an extension of the lighting grid hierarchy method for real-time rendering with many lights on the GPU. We describe efficient methods for parallel construction of the lighting grid hierarchy and using it with deferred rending. We also present a method for estimating shadows from many lights with a small number of shadow samples using the ray tracing API on the GPU. We show how our approach can be used for real-time global illumination computation with virtual point lights.

A pipeline-based heterogeneous framework for efficient synthetic light field rendering

The research interest of real-time global illumination has increased due to the growing demand of graphics applications such as virtual reality. Recently, the design that combines Image-Based Rendering (IBR) and Ray-Tracing to create Synthetic Light Field (SLF) has been widely adopted to provide delicate visual experience for multiple viewpoints at an acceptable frame rate. However, despite its parallel characteristic, constructing a SLF is still inefficient on modern Graphics Processing Unit (GPU) due to the irregularities. For instance, the issues caused by branch divergence, early-termination and irregular memory access prolong the execution time that cannot be simply resolved by workload merging. In this paper, we proposed a Runtime framework that reorganizes the execution into a pipeline-based pattern with grouping of primary rays. The workloads are later distributed to all heterogeneous cores to increase the efficiency of the execution. With this approach, the number of valid rays can be maintained at a high level with less divergence of paths. Based on the experiment on a heterogeneous system, the maximum throughput for a single GPU becomes 3.12 times higher than the original on average and becomes even higher on systems with multiple heterogeneous cores.

Real-time global illumination by precomputed local reconstruction from sparse radiance probes

We present a direct-to-indirect transport technique that enables accurate real-time rendering of indirect illumination in mostly static scenes of complexity on par with modern games while supporting fully dynamic lights, cameras and diffuse surface materials. Our key contribution is an algorithm for reconstructing the incident radiance field from a sparse set of local samples --- radiance probes --- by incorporating mutual visibility into the reconstruction filter. To compute global illumination, we factorize the direct-to-indirect transport operator into global and local parts, sample the global transport with sparse radiance probes at real-time, and use the sampled radiance field as input to our precomputed local reconstruction operator to obtain indirect radiance. In contrast to previous methods aiming to encode the global direct-to-indirect transport operator, our precomputed data is local in the sense that it needs no long-range interactions between probes and receivers, and every receiver depends only on a small, constant number of nearby radiance probes, aiding compression, storage, and iterative workflows. While not as accurate, we demonstrate that our method can also be used for rendering indirect illumination on glossy surfaces, and approximating global illumination in scenes with large-scale dynamic geometry.

Dreamspace: A Platform and Tools for Collaborative Virtual Production

This paper describes the concepts and results implemented by the European FP7 Dreamspace project. Dreamspace develops a new platform and tools for collaborative virtual production of visual effects in film and TV and new immersive experiences. The aim of the project is to enable creative professionals to combine live performances, video, and computer-generated imagery in realtime. In particular, the project has developed tools allowing on-set manipulation of 3D assets, live integration of video feeds from tracked cameras, and live-compositing of either computer-generated imagery (CGI) content or background plates from panoramic video captured by omnidirectional video rigs. The CGI content is lit by automatically captured studio lighting, using a new realtime global illumination rendering system. Furthermore, Dreamspace investigates the use of omnidirectional video and 3D assets in new immersive user experiences.

Forward Light Cuts: A Scalable Approach to Real-Time Global Illumination

We present Forward Light Cuts, a novel approach to real-time global illumination using forward rendering techniques. We focus on unshadowed diffuse interactions for the first indirect light bounce in the context of large models such as the complex scenes usually encountered in CAD application scenarios. Our approach efficiently generates and uses a multiscale radiance cache by exploiting the geometry-specific stages of the graphics pipeline, namely the tessellator unit and the geometry shader To do so, we assimilate virtual point lights to the scene's triangles and design a stochastic decimation process chained with a partitioning strategy that accounts for both close-by strong light reflections, and distant regions from which numerous virtual point lights collectively contribute strongly to the end pixel. Our probabilistic solution is supported by a mathematical analysis and a number of experiments covering a wide range of application scenarios. As a result, our algorithm requires no precomputation of any kind, is compatible with dynamic view points, lighting condition, geometry and materials, and scales to tens of millions of polygons on current graphics hardware.

Virtual Spherical Gaussian Lights for Real-time Glossy Indirect Illumination

Virtual point lights VPLs are well established for real-time global illumination. However, this method suffers from spiky artifacts and flickering caused by singularities of VPLs, highly glossy materials, high-frequency textures, and discontinuous geometries. To avoid these artifacts, this paper introduces a virtual spherical Gaussian light VSGL which roughly represents a set of VPLs. For a VSGL, the total radiant intensity and positional distribution of VPLs are approximated using spherical Gaussians and a Gaussian distribution, respectively. Since this approximation can be computed using summations of VPL parameters, VSGLs can be dynamically generated using mipmapped reflective shadow maps. Our VSGL generation is simple and independent from any scene geometries. In addition, reflected radiance for a VSGL is calculated using an analytic formula. Hence, we are able to render one-bounce glossy interreflections at real-time frame rates with smaller artifacts.

Real-Time Global Illumination Rendering for Mesostructure Surface Based on Gradient Map

PDF HTML阅读 XML下载 导出引用 引用提醒 基于梯度图的微结构表面全局光照实时绘制 DOI: 10.3724/SP.J.1001.2011.03881 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(60842001); 北京市科技新星计划(2009B09); 澳门科学技术发展基金(043/2009/A2) Real-Time Global Illumination Rendering for Mesostructure Surface Based on Gradient Map Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:针对带有微结构表面的几何模型全局光照计算复杂、难以达到实时性要求的问题,提出一种基于高度梯度图分析的全局光照实时绘制方法.首先,定义微结构高度梯度图,并据此构建可见点的局部最高点集合.其次,给出面向微结构表面对象实时绘制的全局光照计算模型,将光照计算近似分解为环境光入射、光源直接光照和一次交互漫反射这3 种分量的计算.在环境光计算过程中,提出一种自适应环境光遮挡计算,借助局部最高点集合计算遮挡角.在直接光照中,给出一种微结构阴影的修正方法,搜索入射光方向的最近局部最高点剖面;通过比较剖面内光线投影与局部最高点的遮挡角,近似确定由微结构造成的阴影区域.最后,根据可见点的局部最高点集合确定一次交互漫反射的采样范围,进行渗色处理.整个全局光照计算方法在图像空间完成,较好地利用了延迟着色的思想和GPU 并行计算的特点.算法可以在使用低精度几何模型时表现出带有微结构表面的高精度模型的全局光照效果,且适用于动态场景和可变形物体的全局光照计算. Abstract:Rendering global illumination for objects with mesostructure surfaces is a time-consuming task and cannot presently be applied to interactive graphics. This paper presents a real-time rendering method, based on a mesostructure height gradient map (MHGM), to exhibit lighting effects on meso-scale detail level in dynamic environments. This paper approximates global illumination by using a lighting model that includes specific characteristics: Incident ambient light, direct light, and a single bounce indirect light. In order to compute these three components in real time, this paper introduces the MHGM to create local apex sets, with which an adaptivemethod for calculating ambient occlusion is proposed. In direct lighting, the nearest local apex profile of the incident rays is to be found and presented as a mesostructure shadow algorithm, which can generate the shadow of meso-scale details. The color of the points enclosed by the local apexes is also sampled to estimate a single bounce indirect light. This approach runs entirely on the graphics hardware and uses deferred shading and the graphicspipeline to accelerate computation. High quality results, which can render meso-scale details with global illumination even for low-resolution geometric models, are achieved. Moreover, this approach fully supports dynamic scenes and deformable objects. 参考文献 相似文献 引证文献

Real-Time Global Illumination Rendering with Dynamic Materials

PDF HTML阅读 XML下载 导出引用 引用提醒 可变材质的实时全局光照明绘制 DOI: 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: Supported by the National Basic Research Program of China under Grant No.2002CB312105 (国家重点基础研究发展计划(973)); the National Natural Science Foundation of China under Grant No.60533080 (国家自然科学基金) Real-Time Global Illumination Rendering with Dynamic Materials Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:现有的基于预计算的全局光照明绘制算法都假设场景中物体的材质固定不变,这样,从入射光照到出射的辐射亮度之间的传输变换就是线性变换.通过对这种线性变换的预计算,可以在动态光源下实现全局光照明的实时绘制.但是,当材质可以改变时,这种线性变换不再成立,因此,现有算法无法直接用于动态材质的场景.提出了一种方法:在修改场景中的物体材质时,可以实时得到场景在直接光照和间接光照下的绘制效果.将最终到达视点的辐射亮度根据其之前经过的反射次数及相应的反射材质分为多个部分,每个部分和先后反射的材质的乘积成正比,从而把该非线性问题转化为线性问题.又将所有可选的材质都表示为一组基的线性组合.将这组基作为材质赋予场景中的物体,就有各种不同的组合方式,预计算每种组合下所有部分的出射辐射亮度.在绘制时,根据各物体材质投影到基上的系数线性组合预计算的数据就能实时得到最终的全局光照明的绘制结果.该方法适用于几何场景、光照和视点都不发生变化的场景.使用双向反射分布函数来表示物体的材质,不考虑折射或者半透明的情况.该实现最多包含两次反射,并可以实时绘制得到一些很有趣的全局光照明效果,比如渗色、焦散等等. Abstract:All previous algorithms of real-time global illumination rendering based on precomputation assume that the materials are invariant, which makes the transfer from lighting to outgoing radiance a linear transformation. By precomputing the linear transformation, real-time global illumination rendering can be achieved under dynamic lighting. This linearity does not hold when materials change. So far, there are no algorithms applicable to scenes with dynamic materials. This paper introduces a real-time rendering method for scenes with editable materials under direct and indirect illumination. The outgoing radiance is separated into different parts based on the times and corresponding materials of reflections. Each part of radiance is linear dependent on the product of the materials along its path of reflections. So the nonlinear problem is converted to a linear one. All materials available are represented as linear combinations of a basis. The basis is applied to the scene to get numbers of different material distributions. For each material distribution, all parts of radiance are precomputed. This paper simply linear combines the precomputed data by coefficients of materials on basis to achieve the effects of global illumination in real-time. This method is applied to scenes with fixed geometry, fixed lighting and fixed view direction. And the materials are represented with bidirectional reflectance distribution functions (BRDFs), which do not take refraction or translucency into account. The authors can simulate in real-time frame rates up to two bounces of light in the implementation, and some interesting phenomena of global illumination, such as color bleeding and caustics, can be achieved. 参考文献 相似文献 引证文献

Real-Time Global Illumination for VR Applications

Real-time global illumination in VR systems enhances scene realism by incorporating soft shadows, reflections of objects in the scene, and color bleeding. The Virtual Light Field (VLF) method enables real-time global illumination rendering in VR. The VLF has been integrated with the Extreme VR system for real-time GPU-based rendering in a Cave Automatic Virtual Environment.

A Fast Ambient Occlusion Method for Real-Time Plant Rendering

Global illumination effects are crucial for virtual plant rendering. Whereas real-time global illumination rendering of plants is impractical, ambient occlusion is an efficient alternative approximation. A tree model with millions of triangles is common, and the triangles can be considered as randomly distributed. The existing ambient occlusion methods fail to apply on such a type of object. In this paper, we present a new ambient occlusion method dedicated to real time plant rendering with limited user interaction. This method is a three-step ambient occlusion calculation framework which is suitable for a huge number of geometry objects distributed randomly in space. The complexity of the proposed algorithm is O(n), compared to the conventional methods with complexities of O(n2). Furthermore, parameters in this method can be easily adjusted to achieve flexible ambient occlusion effects. With this ambient occlusion calculation method, we can manipulate plant models with millions of organs, as well as geometry objects with large number of randomly distributed components with affordable time, and with perceptual quality comparable to the previous ambient occlusion methods.