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.     

A Bayesian Monte Carlo Approach to Global Illumination

Most Monte Carlo rendering algorithms rely on importance sampling to reduce the variance of estimates. Importance sampling is efficient when the proposal sample distribution is well‐suited to the form of the integrand but fails otherwise. The main reason is that the sample location information is not exploited. All sample values are given the same importance regardless of their proximity to one another. Two samples falling in a similar location will have equal importance whereas they are likely to contain redundant information. The Bayesian approach we propose in this paper uses both the location and value of the data to infer an integral value based on a prior probabilistic model of the integrand. The Bayesian estimate depends only on the sample values and locations, and not how these samples have been chosen. We show how this theory can be applied to the final gathering problem and present results that clearly demonstrate the benefits of Bayesian Monte Carlo.     

Instant Caching for Interactive Global Illumination

The ability to interactively render dynamic scenes with global illumination is one of the main challenges in computer graphics. The improvement in performance of interactive ray tracing brought about by significant advances in hardware and careful exploitation of coherence has rendered the potential of interactive global illumination a reality. However, the simulation of complex light transport phenomena, such as diffuse interreflections, is still quite costly to compute in real time. In this paper we present a caching scheme, termed Instant Caching, based on a combination of irradiance caching and instant radiosity. By reutilising calculations from neighbouring computations this results in a speedup over previous instant radiosity‐based approaches. Additionally, temporal coherence is exploited by identifying which computations have been invalidated due to geometric transformations and updating only those paths. The exploitation of spatial and temporal coherence allows us to achieve superior frame rates for interactive global illumination within dynamic scenes, without any precomputation or quality loss when compared to previous methods; handling of lighting and material changes are also demonstrated.     

Efficient Glossy Global Illumination with Interactive Viewing

The ability to perform interactive walkthroughs of global illumination solutions including glossy effects is a challenging open problem. In this paper we overcome certain limitations of previous approaches. We first introduce a novel, memory- and compute-efficient representation of incoming illumination, in the context of a hierarchical radiance clustering algorithm. We then represent outgoing radiance with an adaptive hierarchical basis, in a manner suitable for interactive display. Using appropriate refinement and display strategies, we achieve walkthroughs of glossy solutions at interactive rates for non-trivial scenes. In addition, our implementation has been developed to be portable and easily adaptable as an extension to existing, diffuse-only, hierarchical radiosity systems. We present results of the implementation of glossy global illumination in two independent global illumination systems.     

A Vector Approach for Global Illumination in Ray Tracing

This paper presents a method taking global illumination into account in a ray tracing environment. A vector approach is introduced, which allows to deal with all the types of light paths and the directional properties of materials. Three types of vectors are defined: Direct Light Vectors associated to light sources, Indirect Light Vectors which correspond to light having been diffusely reflected at least once and Caustic Light Vectors which are associated to light rays emitted by sources and reflected and/or transmitted by specular surfaces. These vectors are estimated at a small number of points in the scene. A weighted interpolation between known values allows to reconstruct these vectors for the other points, with the help of a gradient computation for the indirect component. This approach also allows to take uniform area light sources (spherical, rectangular and circular) into account for all the types of vectors. Computed images are thus more accurate and no discretizing of the geometry of the scene is needed.     

Interactive Global Illumination for Deformable Geometry in CUDA

Interactive global illumination for fully deformable scenes with dynamic relighting is currently a very elusive goal in the area of realistic rendering. In this work we propose a system that is based on explicit visibility calculations and which is highly efficient and scalable. The rendering equation defines the light exchange between surfaces, which we approximate by subsampling. By utilizing the power of modern parallel GPUs using the CUDA framework we achieve interactive frame rates. Since we update the global illumination continuously in an asynchronous fashion, we maintain interactivity at all times for moderately complex scenes. We show that we can achieve higher frame rates for scenes with moving light sources, diffuse indirect illumination and dynamic geometry than other current methods, while maintaining a high image quality.     

A Scalable Approach to Evolvable Hardware

Evolvable Hardware (EHW) has been proposed as a new method for designing systems for complex real-world applications. However, so far, only relatively simple systems have been shown to be evolvable. In this paper, it is proposed that concepts from biology should be applied to EHW techniques to make EHW more applicable to solving complex problems. One such concept has led to the increased complexity scheme presented, where a system is evolved by evolving smaller sub-systems. Experiments with two different tasks illustrate that inclusion of this scheme substantially reduces the number of generations required for evolution. Further, for the prosthesis control task, the best performance is obtained by the novel approach. The best circuit evolved performs better than the best trained neural network.     

Interactive Display of Global Illumination Solutions for Non-diffuse Environments – A Survey

In recent years there has been a lot of work on interactively displaying global illumination solutions for non-diffuse environments. This is an extremely active field of research, in which a lot of different approaches have recently been proposed. In this survey, we will discuss and compare these. This will hopefully prepare the ground for systematically addressing the open questions in the future.     

Guided Image Filtering for Interactive High‐quality Global Illumination

Interactive computation of global illumination is a major challenge in current computer graphics research. Global illumination heavily affects the visual quality of generated images. It is therefore a key attribute for the perception of photo‐realistic images. Path tracing is able to simulate the physical behaviour of light using Monte Carlo techniques. However, the computational burden of this technique prohibits interactive rendering times on standard commodity hardware in high‐quality. Trying to solve the Monte Carlo integration with fewer samples results in characteristic noisy images. Global illumination filtering methods take advantage of the fact that the integral for neighbouring pixels may be very similar. Averaging samples of similar characteristics in screen‐space may approximate the correct integral, but may result in visible outliers. In this paper, we present a novel path tracing pipeline based on an edge‐aware filtering method for the indirect illumination which produces visually more pleasing results without noticeable outliers. The key idea is not to filter the noisy path traced images but to use it as a guidance to filter a second image composed from characteristic scene attributes that do not contain noise by default. We show that our approach better approximates the Monte Carlo integral compared to previous methods. Since the computation is carried out completely in screen‐space it is therefore applicable to fully dynamic scenes, arbitrary lighting and allows for high‐quality path tracing at interactive frame rates on commodity hardware.     

A Systematic Approach to Interactive Programming

Designed for program development in an interactive environment, this framework can help create a new generation of programmers with an invaluable disciplined approach to software development.     

State of the Art in Global Illumination for Interactive Applications and High-quality Animations

Global illumination algorithms are regarded as computationally intensive. This cost is a practical problem when producing animations or when interactions with complex models are required. Several algorithms have been proposed to address this issue. Roughly, two families of methods can be distinguished. The first one aims at providing interactive feedback for lighting design applications. The second one gives higher priority to the quality of results, and therefore relies on offline computations. Recently, impressive advances have been made in both categories. In this report, we present a survey and classification of the most up‐to‐date of these methods. ACM CSS: I.3.7 Computer Graphics—Three‐Dimensional Graphics and Realism     

一种面向并行实现的全局光照算法

提出了种适合于并行实现的全局光照算法。对真实感图象的实时生成和交互式性运行进行了有益的探索,算法主要由两个模块组成;粒子跟踪过程,网格优化与密度估计过程,在此进行了详细介绍。另外,给出算法实际运行得到的具有高度真实感的生成图象。     

A Scalable Approach for Variational Data Assimilation

Data assimilation (DA) is a methodology for combining mathematical models simulating complex systems (the background knowledge) and measurements (the reality or observational data) in order to improve the estimate of the system state (the forecast). The DA is an inverse and ill posed problem usually used to handle a huge amount of data, so, it is a large and computationally expensive problem. Here we focus on scalable methods that makes DA applications feasible for a huge number of background data and observations. We present a scalable algorithm for solving variational DA which is highly parallel. We provide a mathematical formalization of this approach and we also study the performance of the resulted algorithm.     

Multi‐Image Based Photon Tracing for Interactive Global Illumination of Dynamic Scenes

Image space photon mapping has the advantage of simple implementation on GPU without pre‐computation of complex acceleration structures. However, existing approaches use only a single image for tracing caustic photons, so they are limited to computing only a part of the global illumination effects for very simple scenes. In this paper we fully extend the image space approach by using multiple environment maps for photon mapping computation to achieve interactive global illumination of dynamic complex scenes. The two key problems due to the introduction of multiple images are 1) selecting the images to ensure adequate scene coverage; and 2) reliably computing ray‐geometry intersections with multiple images. We present effective solutions to these problems and show that, with multiple environment maps, the image‐space photon mapping approach can achieve interactive global illumination of dynamic complex scenes. The advantages of the method are demonstrated by comparison with other existing interactive global illumination methods.     

Global Illumination Shadow Layers

Computer graphics artists often resort to compositing to rework light effects in a synthetic image without requiring a new render. Shadows are primary subjects of artistic manipulation as they carry important stylistic information while our perception is tolerant with their editing. In this paper we formalize the notion of global shadow, generalizing direct shadow found in previous work to a global illumination context. We define an object's shadow layer as the difference between two altered renders of the scene. A shadow layer contains the radiance lost on the camera film because of a given object. We translate this definition in the theoretical framework of Monte‐Carlo integration, obtaining a concise expression of the shadow layer. Building on it, we propose a path tracing algorithm that renders both the original image and any number of shadow layers in a single pass: the user may choose to separate shadows on a per‐object and per‐light basis, enabling intuitive and decoupled edits.     

Searching a Scalable Approach to Cerebellar Based Control

Decades of research into the structure and function of the cerebellum have led to a clear understanding of many of its cells, as well as how learning might take place. Furthermore, there are many theories on what signals the cerebellum operates on, and how it works in concert with other parts of the nervous system. Nevertheless, the application of computational cerebellar models to the control of robot dynamics remains in its infant state. To date, few applications have been realized. The currently emerging family of light-weight robots (Hirzinger, in Proc. Second ecpd Int. Conference on Advanced Robotics, Intelligent Automation and Active Systems, 1996) poses a new challenge to robot control: due to their complex dynamics traditional methods, depending on a full analysis of the dynamics of the system, are no longer applicable since the joints influence each other dynamics during movement. Can artificial cerebellar models compete here?     

Factorized Point Based Global Illumination

The Point‐Based Global Illumination (PBGI) algorithm is composed of two major steps: a caching step and a multiview rasterization step. At caching time, a dense point‐sampling of the scene is shaded and organized in a spatial hierarchy, with internal nodes approximating the radiance of their subtrees using spherical harmonics. At rasterization time, a microbuffer is instantiated at the unprojected position of each image pixel (receiver). Then, a view‐adaptive level‐of‐detail of the scene is extracted in the form of a tree cut and rasterized in the receiver's microbuffer, solving for visibility using a local variant of the z‐buffer. Finally, the pixel color is computed by convolving its filled microbuffer with the surface BRDF. This noise‐free indirect lighting method is widely used in the industry and captures several critical lighting effects, including ambient occlusion, color bleeding, (indirect) soft‐shadows and environment lighting. However, we observe a large redundancy in this algorithm, both in cuts and receivers'microbuffers, which stems from their relatively low resolution. In this paper, we propose an evolution of PBGI which exploits spatial coherence to reduce these redundant computations. Starting from a similarity‐based variational clustering of the receivers, we compute a single tree cut and rasterize a single microbuffer for each cluster. This per‐cluster microbuffer provides a faithful approximation of the incident radiance for distant nodes and is composited over a receiver‐specific microbuffer rasterizing only the closest nodes of the cluster's cut. This factorized approach is easy to integrate in any existing PBGI implementation and offers a significant rendering speed‐up for a negligible and controllable approximation error.     

Interactive Indirect Illumination Using Voxel Cone Tracing

Indirect illumination is an important element for realistic image synthesis, but its computation is expensive and highly dependent on the complexity of the scene and of the BRDF of the involved surfaces. While off‐line computation and pre‐baking can be acceptable for some cases, many applications (games, simulators, etc.) require real‐time or interactive approaches to evaluate indirect illumination. We present a novel algorithm to compute indirect lighting in real‐time that avoids costly precomputation steps and is not restricted to low‐frequency illumination. It is based on a hierarchical voxel octree representation generated and updated on the fly from a regular scene mesh coupled with an approximate voxel cone tracing that allows for a fast estimation of the visibility and incoming energy. Our approach can manage two light bounces for both Lambertian and glossy materials at interactive framerates (25–70FPS). It exhibits an almost scene‐independent performance and can handle complex scenes with dynamic content thanks to an interactive octree‐voxelization scheme. In addition, we demonstrate that our voxel cone tracing can be used to efficiently estimate Ambient Occlusion.     

A DHT-Based Identifier-to-Locator Mapping Approach for a Scalable Internet

It is commonly recognized that today's Internet routing and addressing system is facing serious scaling problems, which are mainly caused by the overloading of IP address semantics. That is, an IP address represents not only the location but also the identity of a host. To address this problem, several recent schemes propose to replace the IP namespace in today's Internet with a locator namespace and an identity namespace. The locator namespace consists of locators that are used to represent the locations of hosts. On the other hand, the identity namespace consists of identifiers that are used to represent the identities of hosts. For these schemes to work, there must be a mapping system that can supply an appropriate locator for any given end point identifier (EID). While prior related works mainly focus on aggregable EIDs, several recent works proposed the use of self-certifying EIDs for purpose of security and privacy. However, self-certifying EIDs are flat, unstructured and prior proposals cannot be used to deal with flat EIDs. In this paper, we propose a Distributed hash table (DHT)-based identifier-to-locator mapping scheme to resolve a locator for a flat identifier. We evaluate the performance of the proposed scheme. We show that, besides the capability to support flat EIDs, the scheme has good scalability and low resolution delay. We also show that the scheme is robust and can efficiently support mobility.