A Multiprocessor Implementation of Radiosity

This paper describes a multi-processor implementation of form factor computation in the radiosity method. Form factors are computed using the ray casting method and the algorithm is enhanced with Binary Space Partition (BSP) Trees and bounding boxes. Experimental results are presented together with a discussion of load balance efficiency.     

Multiresolution B-spline Radiosity

This paper introduces a kind of new wavelet radiosity method called multiresolution B-spline radiosity, which uses B-splines of different scales to represent radiosity distribution functions. A set of techniques and algorithms, such as function extrapolation, adaptive quadrature, scale adjustment and octree, are proposed to implement it. This method sets up hierarchical structures on surfaces, keeps radiosity distribution continuous at element boundaries, does not need postprocessing, and does not prevent the use of any surface whose parameter domain is rectilinear.     

Wavelet Projections for Radiosity

One important goal of image synthesis research is to accelerate the process of obtaining realistic images using the radiosity method. Two important concepts recently introduced are the general framework of projection methods and the hierarchical radiosity method. Wavelet theory, which explores the space of hierarchical basis functions, offers an elegant framework that unites these two concepts and allows us to more formally understand the hierarchical radiosity method. Wavelet expansions of the radiosity kernel have negligible entries in regions where high frequency/fine detail information is not needed. A sparse system remains if these entries are ignored. This is similar to applying a lossy compression scheme to the form factor matrix. The sparseness of the system allows for asymptotically faster radiosity algorithms by limiting the number of matrix terms that need to be computed. The application of these methods to 3D environments is described in⁴. Due to space limitations in that paper many of the subtleties of the construction could not be explored there. In this paper we discuss some of the mathematical details of wavelet projections and investigate the application of these methods to the radiosity kernel of a flatland environment, where many aspect are easier to visualize.     

Fast Multipath Radiosity using Hierarchical Subscenes

This paper presents an efficient acceleration technique for the global line radiosity Multipath method. In this approach, the scene is subdivided in a hierarchy of box bounded subscenes, the boxes subdivided in a grid of virtual patches which store angular information. A new recursive (according to the hierarchy of subscenes) function allows to execute the Multipath algorithm at different levels of the hierarchy. A speed up factor up to 3–4 has been obtained on some of the tested scenes.     

Hierarchical Image-Space Radiosity for Interactive Global Illumination

We introduce image-space radiosity and a hierarchical variant as a method for interactively approximating diffuse indirect illumination in fully dynamic scenes. As oft observed, diffuse indirect illumination contains mainly low-frequency details that do not require independent computations at every pixel. Prior work leverages this to reduce computation costs by clustering and caching samples in world or object space. This often involves scene preprocessing, complex data structures for caching, or wasted computations outside the view frustum. We instead propose clustering computations in image space, allowing the use of cheap hardware mipmapping and implicit quadtrees to allow coarser illumination computations. We build on a recently introduced multiresolution splatting technique combined with an image-space lightcut algorithm to intelligently choose virtual point lights for an interactive, one-bounce instant radiosity solution. Intelligently selecting point lights from our reflective shadow map enables temporally coherent illumination similar to results using more than 4096 regularly-sampled VPLs.     

Into the Blue: Better Caustics through Photon Relaxation

The photon mapping method is one of the most popular algorithms employed in computer graphics today. However, obtaining good results is dependent on several variables including kernel shape and bandwidth, as well as the properties of the initial photon distribution. While the photon density estimation problem has been the target of extensive research, most algorithms focus on new methods of optimising the kernel to minimise noise and bias. In this paper we break from convention and propose a new approach that directly redistributes the underlying photons. We show that by relaxing the initial distribution into one with a blue noise spectral signature we can dramatically reduce background noise, particularly in areas of uniform illumination. In addition, we propose an efficient heuristic to detect and preserve features and discontinuities. We then go on to demonstrate how reconfiguration also permits the use of very low bandwidth kernels, greatly improving render times whilst reducing bias.     

Global Illumination using Photon Ray Splatting

We present a novel framework for efficiently computing the indirect illumination in diffuse and moderately glossy scenes using density estimation techniques. Many existing global illumination approaches either quickly compute an overly approximate solution or perform an orders of magnitude slower computation to obtain high-quality results for the indirect illumination. The proposed method improves photon density estimation and leads to significantly better visual quality in particular for complex geometry, while only slightly increasing the computation time. We perform direct splatting of photon rays, which allows us to use simpler search data structures. Since our density estimation is carried out in ray space rather than on surfaces, as in the commonly used photon mapping algorithm, the results are more robust against geometrically incurred sources of bias. This holds also in combination with final gathering where photon mapping often overestimates the illumination near concave geometric features. In addition, we show that our photon splatting technique can be extended to handle moderately glossy surfaces and can be combined with traditional irradiance caching for sparse sampling and filtering in image space.     

Spatial Directional Radiance Caching

We present a new approach for accelerated global illumination computation in scenes with glossy surfaces. Our algorithm combines sparse illumination computation used in the radiance caching algorithm with BRDF importance sampling. To make this approach feasible, we extend the idea of lazy illumination evaluation, used in the caching approaches, from the spatial to the directional domain. Using importance sampling allows us to apply caching not only on low-gloss but also on shiny materials with high-frequency BRDFs, for which the radiance caching algorithm breaks down.     

An Adaptive Method for Indirect Illumination Using Light Vectors

In computer graphics, several phenomema need to be taken into account when it comes to the field of photo-realism. One of the most relevant is obviously the notion of global, and more precisely indirect, illumination. In "classical" ray-tracing if you are not under the light, then you are in a shadow. A great amount of work has been carried out which proposes ray-tracing based solutions to take into account the fact that "there is a certain amount of light in shadows". All of these methods carry the same weaknesses: high computation time and a lot of parameters you need to manage to get something out of the method. This paper proposes a generic computation method of indirect illumination based on Monte Carlo sampling and on the sequential analysis theory, which is faster and more automatic than classical methods.     

A Progressive Radiosity Algorithm for Scenes Containing Curved Surfaces

Based on the theory of light energy transfer between two differential diffuse surface areas, a generalized radiosity approach is presented. Unlike the conventional radiosity method, curved surfaces are subdivided into triangular surface patches, radiosity is assummed to be vary across each triangular surface patch. By adopting linear interpolation scheme over each triangular surface patch, we have established a complete set of approximated radiosity equations. Their unknowns are radiosities of differential surface areas located at all vertices of surface patches. The generalized radiosity equation has also been extended to non-diffuse environments. Theoretical analysis and experimental results demonstrate the great potential of this method,     

An Analysis of Quasi-Monte Carlo Integration Applied to the Transillumination Radiosity Method

This paper presents an enhanced transillumination radiosity method that can provide accurate solutions at relatively low computational cost. The proposed algorithm breaks down the double integral of the gathered power to an area integral that is computed analytically and to a directional integral that is evaluated by quasi-Monte Carlo techniques. Since the analytical integration results in a continuous function of finite variation, the quasi-Monte Carlo integration that follows the analytical integration will be efficient and its error can be bounded by the Koksma-Hlawka inequality. The paper also analyses the requirements of the convergence, presents theoretical error bounds and proposes error reduction techniques. The theoretical bounds are compared with simulation results.     

层次结构辐射度渲染中的可见性测试

在辐射度渲染等整体光照模型中，可见性测试是影响整体性能的关键，为了获得较好的可见性测试效果，在光线投射方法基础上，对可见性测试方法做了如下两方面的优化，一方面引入Shaft Culling算法，作首轮筛选，以提高线投射的效率，另一方面，在可见性测试和自适应分割时，进行基于可见性的分割，以保证只有完全可见和完全不可见两种情况，这两方面优化都被引入到层次结构辐射度渲染的实现中，实验结果表明，改进过的可见性测试，不仅减少了计算量和误差，还保证了阴影边界的质量。     

Radiosity: A method for computing global illumination

The radiosity method for computing the interreflection of light within diffuse environments is described. The development of the method for realistic image synthesis over the past three years is outlined. A short discussion of the underlying theory and implementation is followed by a real life example which illustrates the power and accuracy of the radiosity method and points out the different results from ray tracing procedures. Current and future developments of the radiosity method are outlined.     

MAX渲染算法光线跟踪与光能传递的分析对比

光线跟踪(Raytracer)与光能传递(Radiosity)渲染是3D设计软件中常用的渲染方法,对场景使用光线跟踪与光能传递渲染可以生成十分逼真的光影效果。但两种渲染算法都需要进行大量复杂的运算,尤其是光能传递对计算机系统的性能要求很高,对硬件平台的运算速度和能力都有很苛刻的要求。     

MAX渲染算法光线跟踪与光能传递的分析对比

光线跟踪（Raytracer）与光能传递（Radiosity）渲染是3D设计软件中常用的渲染方法,时场景使用光线跟踪与光能传递渲染可以生成十分逼真的光影效果。但两种渲染算法都需要进行大量复杂的运算,尤其是光能传递时计算机系统的性能要．求很高,时硬件平台的运算速度和能力都有很苛刻的要求。     

可大规模应用的辐射度计算的自动网格化方法

合理地网格化场景是有效地进行辐射度计算的重要前提.现有的两种主要剖分方法是细分法和阴影边界计算法.前者是在必要时对大面片进行自动细分,后者是先解析地求出阴影的区域,然后根据阴影边界进行划分.前者存在的问题是无法检测出落在大面片中间的细节变化,绘制的质量得不到保证.后一种方法又局限于基本上只能处理纯多边形场景,而且计算时间长,实现复杂,难以在工程上进行应用.文章提出一种网格化方法,它面向大规模工程应用,简便易行,并能生成较高质量的图像.这种方法先将能量接受面划分成满足精度要求的细小面元,然后根据各面元对场景中各光源的可见性特征进行合并操作,以使能量变化情况不同的区域能以不同大小的尺寸进行剖分,这样,用于计算的面片大大减少,而图像质量没有明显的降低.实验结果和统计数据表明,此方法因其简单、高效,很适合大规模的工程应用.     

Space-Time Hierarchical Radiosity with Clustering and Higher-Order Wavelets

We address in this paper the issue of computing diffuse global illumination solutions for animation sequences. The principal difficulties lie in the computational complexity of global illumination, emphasized by the movement of objects and the large number of frames to compute, as well as the potential for creating temporal discontinuities in the illumination, a particularly noticeable artifact. We demonstrate how space‐time hierarchical radiosity, i.e. the application to the time dimension of a hierarchical decomposition algorithm, can be effectively used to obtain smooth animations: first by proposing the integration of spatial clustering in a space‐time hierarchy; second, by using a higher‐order wavelet basis adapted for the temporal dimension. The resulting algorithm is capable of creating time‐dependent radiosity solutions efficiently.     

GPU编程模型下的实时辐射度着色方法的分析与探讨

Radiosity是模拟能量在场景中传递,最终达到平衡的一种阴影着色方法.Realtime Radiosity是这种算法在实时场景中的应用,本文总结了目前的两种实时辐射度算法的实现,并分析了各自的优缺点.     

Render2MPEG: A Perception-based Framework Towards Integrating Rendering and Video Compression

Currently 3D animation rendering and video compression are completely independent processes even if rendered frames are streamed on‐the‐fly within a client‐server platform. In such scenario, which may involve time‐varying transmission bandwidths and different display characteristics at the client side, dynamic adjustment of the rendering quality to such requirements can lead to a better use of server resources. In this work, we present a framework where the renderer and MPEG codec are coupled through a straightforward interface that provides precise motion vectors from the rendering side to the codec and perceptual error thresholds for each pixel in the opposite direction. The perceptual error thresholds take into account bandwidth‐dependent quantization errors resulting from the lossy com‐pression as well as image content‐dependent luminance and spatial contrast masking. The availability of the discrete cosine transform (DCT) coefficients at the codec side enables to use advanced models of the human visual system (HVS) in the perceptual error threshold derivation without incurring any significant cost. Those error thresholds are then used to control the rendering quality and make it well aligned with the compressed stream quality. In our prototype system we use the lightcuts technique developed by Walter et al., which we enhance to handle dynamic image sequences, and an MPEG‐2 implementation. Our results clearly demonstrate many advantages of coupling the rendering with video compression in terms of faster rendering. Furthermore, temporally coherent rendering leads to a reduction of temporal artifacts.