Global Illumination Algorithms Research Articles

Temporally Stable Metropolis Light Transport Denoising using Recurrent Transformer Blocks

Metropolis Light Transport (MLT) is a global illumination algorithm that is well-known for rendering challenging scenes with intricate light paths. However, MLT methods tend to produce unpredictable correlation artifacts in images, which can introduce visual inconsistencies for animation rendering. This drawback also makes it challenging to denoise MLT renderings while maintaining temporal stability. We tackle this issue with modern learning-based methods and build a sequence denoiser combining the recurrent connections with the cutting-edge vision transformer architecture. We demonstrate that our sophisticated denoiser can consistently improve the quality and temporal stability of MLT renderings with difficult light paths. Our method is efficient and scalable for complex scene renderings that require high sample counts.

Graphical Heatmap-Based Approach to Indoor Radio Signal Propagation: Adapting Advanced Ray Tracing and Global Illumination Algorithms

Graphical Heatmap-Based Approach to Indoor Radio Signal Propagation: Adapting Advanced Ray Tracing and Global Illumination Algorithms

Approximate global illumination using photon mapping: A review

This paper introduces the two-step process of the standard photon mapping algorithm and a variety of other global biased illumination algorithms using photon mapping that have been proposed in recent years. Since there are many global biased illumination algorithms based on photon mapping, this review is a combination of these algorithms for the convenience of the reader, and the two-step process of standard PM will also be presented in this review to accommodate readers who are not familiar with the field. We will first introduce the specific implementation process and principles based on the two steps of PM, photon tracking and rendering, and then introduce a variety of polarized illumination techniques using photon maps, compare these methods and discuss the advantages, disadvantages, and applicability of each method in detail, and finally give a specific implementation of each method to give readers a clearer understanding of these methods. The final implementation of each method is shown to give the reader a clearer understanding of these methods.

Constructing K-d Tree on GPU through Treelet Restructuring

With every new generation of graphics processing units (GPUs), offloading ray-tracing algorithms to GPUs becomes more feasible. Software-hardware solutions for ray-tracing focus on implementing its basic components, such as building and traversing bounding volume hierarchies (BVH). However, global illumination algorithms, such as photon mapping method, depend on another kind of acceleration structure, namely k-d trees. In this work, we adapt state-ofthe-art GPU-based BVH-building algorithm of treelet restructuring to k-d trees. By evaluating the performance of the resulting k-d tree, we show that treelet optimisation heuristic suitable for BVHs of triangles is inadequate for k-d trees of points.

Adaptive Matrix Completion for Fast Visibility Computations with Many Lights Rendering

AbstractSeveral fast global illumination algorithms rely on the Virtual Point Lights framework. This framework separates illumination into two steps: first, propagate radiance in the scene and store it in virtual lights, then gather illumination from these virtual lights. To accelerate the second step, virtual lights and receiving points are grouped hierarchically, for example using Multi‐Dimensional Lightcuts. Computing visibility between clusters of virtual lights and receiving points is a bottleneck. Separately, matrix completion algorithms reconstruct completely a low‐rank matrix from an incomplete set of sampled elements. In this paper, we use adaptive matrix completion to approximate visibility information after an initial clustering step. We reconstruct visibility information using as little as 10 % to 20 % samples for most scenes, and combine it with shading information computed separately, in parallel on the GPU. Overall, our method computes global illumination 3 or more times faster than previous state‐of‐the‐art methods.

Heuristic based real-time hybrid rendering with the use of rasterization and ray tracing method

Abstract Nowadays, rasterization is the most common method used to achieve real-time semi-photorealistic effects in games or interactive applications. Some of those effects are not easily achievable, thus require more complicated methods and are difficult to obtain. The appearance of the presented worlds depends to a large extent on the approximation to the physical basis of light behaviour in them. The best effects in this regard are global illumination algorithms. Each of them including ray tracing give the most plausible effects, but at cost of higher computational complexity. Today’s hardware allows usage of ray tracing methods in-real time on Graphics Processing Units (GPU) thanks to its parallel nature. However, using ray tracing as a single rendering method may still result in poor performance, especially when used to create many image effects in complex environments. In this paper we present a hybrid approach for real-time rendering using both rasterization and ray tracing using heuristic, which determines whether to render secondary effects such as shadows, reflections and refractions for individual objects considering their relevancy and cost of rendering those effects for these objects in particular case.

RenderMan

Pixar’s RenderMan renderer is used to render all of Pixar’s films and by many film studios to render visual effects for live-action movies. RenderMan started as a scanline renderer based on the Reyes algorithm, and it was extended over the years with ray tracing and several global illumination algorithms. This article describes the modern version of RenderMan, a new architecture for an extensible and programmable path tracer with many features that are essential to handle the fiercely complex scenes in movie production. Users can write their own materials using a bxdf interface and their own light transport algorithms using an integrator interface—or they can use the materials and light transport algorithms provided with RenderMan. Complex geometry and textures are handled with efficient multi-resolution representations, with resolution chosen using path differentials. We trace rays and shade ray hit points in medium-sized groups, which provides the benefits of SIMD execution without excessive memory overhead or data streaming. The path-tracing architecture handles surface, subsurface, and volume scattering. We show examples of the use of path tracing, bidirectional path tracing, VCM, and UPBP light transport algorithms. We also describe our progressive rendering for interactive use and our adaptation of denoising techniques.

Screen Space Ambient Occlusion Based Multiple Importance Sampling for Real-Time Rendering

We propose a new approximation technique for accelerating the Global Illumination algorithm for real-time rendering. The proposed approach is based on the Screen-Space Ambient Occlusion (SSAO) method, which approximates the global illumination for large, fully dynamic scenes at interactive frame rates. Current algorithms that are based on the SSAO method suffer from difficulties due to the large number of samples that are required. In this paper, we propose an improvement to the SSAO technique by integrating it with a Multiple Importance Sampling technique that combines a stratified sampling method with an importance sampling method, with the objective of reducing the number of samples. Experimental evaluation demonstrates that our technique can produce high-quality images in real time and is significantly faster than traditional techniques.

Energy-efficient global illumination algorithms for mobile devices using dynamic voltage and frequency scaling

With increases of display resolution and graphical quality demands, global illumination techniques are sought after to meet such demands. However, global illumination algorithms have a long processing time on mobile devices, such as smartphones or tablet PCs. Besides the performance issue, the algorithms consume a large amount of battery-powered energy. The performance and energy consumption have a trade-off relationship. The dynamic voltage and frequency scaling (DVFS) algorithms control the balance between the performance and the energy consumption by adjusting the GPU and CPU’s frequencies. To improve the performance of the global illumination algorithm and reduce the high energy consumption of the current DVFS algorithm, we suggest new algorithms with new metrics for estimating the amount of workload for GPUs as well as their memory workload. Using our new DVFS algorithms, we increase the energy efficiency, the performance per watt, of a global illumination algorithm by 33.59% in comparison to a conventional general-purpose DVFS algorithm, without modifying the underlying algorithm core.

Sequential Monte Carlo Instant Radiosity.

Instant Radiosity and its derivatives are interactive methods for efficiently estimating global (indirect) illumination. They represent the last indirect bounce of illumination before the camera as the composite radiance field emitted by a set of virtual point light sources (VPLs). In complex scenes, current algorithms suffer from a difficult combination of two issues: it remains a challenge to distribute VPLs in a manner that simultaneously gives a high-quality indirect illumination solution for each frame, and to do so in a temporally coherent manner. We address both issues by building, and maintaining over time, an adaptive and temporally coherent distribution of VPLs in locations where they bring indirect light to the image. We introduce a novel heuristic sampling method that strives to only move as few of the VPLs between frames as possible. The result is, to the best of our knowledge, the first interactive global illumination algorithm that works in complex, highly-occluded scenes, suffers little from temporal flickering, supports moving cameras and light sources, and is output-sensitive in the sense that it places VPLs in locations that matter most to the final result.

Variance Analysis and Adaptive Sampling for Indirect Light Path Reuse

In this paper, we study the estimation variance of a set of global illumination algorithms based on indirect light path reuse. These algorithms usually contain two passes — in the first pass, a small number of indirect light samples are generated and evaluated, and they are then reused by a large number of reconstruction samples in the second pass. Our analysis shows that the covariance of the reconstruction samples dominates the estimation variance under high reconstruction rates and increasing the reconstruction rate cannot effectively reduce the covariance. We also find that the covariance represents to what degree the indirect light samples are reused during reconstruction. This analysis motivates us to design a heuristic approximating the covariance as well as an adaptive sampling scheme based on this heuristic to reduce the rendering variance. We validate our analysis and adaptive sampling scheme in the indirect light field reconstruction algorithm and the axis-aligned filtering algorithm for indirect lighting. Experiments are in accordance with our analysis and show that rendering artifacts can be greatly reduced at a similar computational cost.

움직이는 물체의 개수에 비례하는 시간을 가지는 전역조명 알고리즘

움직이는 물체의 개수에 비례하는 시간을 가지는 전역조명 알고리즘

Lighting-driven voxels for memory-efficient computation of indirect illumination

Several recently proposed voxel-based global illumination algorithms rely on the use of reflective shadow maps (RSMs) to interactively compute indirect illumination. However, RSMs do not scale well...

Efficient Quadrature Rules for Illumination Integrals: From Quasi Monte Carlo to Bayesian Monte Carlo

Rendering photorealistic images is a costly process which can take up to several days in the case of high quality images. In most cases, the task of sampling the incident radiance function to evaluate the illumination integral is responsible for an important share of the computation time. Therefore, to reach acceptable rendering times, the illumination integral must be evaluated using a limited set of samples. Such a restriction raises the question of how to obtain the most accurate approximation possible with such a limited set of samples. One must thus ensure that sampling produces the highest amount of information possible by carefully placing and weighting the limited set of samples. Furthermore, the integral evaluation should take into account not only the information brought by sampling but also possible information available prior to sampling, such as the integrand smoothness. This idea of sparse information and the need to fully exploit the little information available is present throughout this book. The presented methods correspond to the state-of-the-art solutions in computer graphics, and take into account information which had so far been underexploited (or even neglected) by the previous approaches. The intended audiences are Ph.D. students and researchers in the field of realistic image synthesis or global illumination algorithms, or any person with a solid background in graphics and numerical techniques.

Complex Luminaires

Simulating a complex luminaire such as a chandelier is expensive and slow, even using state-of-the-art algorithms. A more practical alternative is to use precomputation to accelerate rendering. Prior approaches cached information on an aperture surface that separates the luminaire from the scene, but many luminaires have large or ill-defined apertures leading to excessive data storage and inaccurate results. In this article, we separate luminaire rendering into illumination and appearance components. A precomputation stage simulates the complex light flow inside the luminaire to generate two data structures: a set of anisotropic point lights (APLs) and a radiance volume. The APLs are located near apparent sources and represent the light leaving the luminaire, allowing its nearand far-field illumination to be accurately and efficiently computed at render time. The luminaire's appearance consists of high- and low-frequency components, which are both visually important. High-frequency components are computed dynamically at render time, while the more computationally expensive low-frequency components are approximated using the precomputed radiance volume. Results are shown for several complex luminaires, demonstrating orders of magnitude faster rendering compared to the best global illumination algorithms and higher fidelity with greatly reduced storage requirements compared to previous precomputed approaches.

Coherent Photon Mapping on the Intel MIC Architecture

Photon mapping is a global illumination algorithm which is composed of two steps: photon tracing and photon searching. During photon searching step, each shading point needs to search the photon-tree to find k-neighbouring photons for reflected radiance estimation. As the number of shading points and the size of photon-tree are dramatically large, the photon searching step is time consuming. We propose a parallel photon searching algorithm by using radiance estimation approach for coherent shading points on the Intel® Many Integrated Core (MIC) Architecture. In order to efficiently use single instruction multiple data (SIMD) units, shading points are clustered by similarity first (every cluster contains 16 shading-points), and an initial neighbouring scope is searched from the photon-tree for each cluster. Then we use 16-wide SIMD units by performing k-NN searching from the initial neighbouring scope for those 16 shading-points in a cluster in parallel. We use the method to simulate some global illumination scenes on Intel® Xeon® processors and Intel® Xeon® Phi™ coprocessors. The comparison results with existing photon mapping techniques indicate that our method gives significant improvement in speed with the same accuracy.

Multiplexed metropolis light transport

Global illumination algorithms using Markov chain Monte Carlo (MCMC) sampling are well-known for their efficiency in scenes with complex light transport. Samples in such algorithms are generated as a history of Markov chain states so that they are distributed according to the contributions to the image. The whole process is done based only on the information of the path contributions and user-defined transition probabilities from one state to the others. In light transport simulation, however, there is more information that can be used to improve the efficiency of path sampling. A notable example is multiple importance sampling (MIS) in bidirectional path tracing, which utilizes the probability densities of constructing a given path with different estimators. While MIS is a powerful ordinary Monte Carlo method, how to incorporate such additional information into MCMC sampling has been an open problem. We introduce a novel MCMC sampling framework, primary space serial tempering , which fuses the ideas of MCMC sampling and MIS for the first time. The key idea is to explore not only the sample space using a Markov chain, but also different estimators to generate samples by utilizing the information already available for MIS. Based on this framework, we also develop a novel rendering algorithm, multiplexed Metropolis light transport , which automatically and adaptively constructs paths with appropriate techniques as predicted by MIS. The final algorithm is very easy to implement, yet in many cases shows comparable (or even better) performance than significantly more complex MCMC rendering algorithms.

Computer graphics: principles and practice

1. Introduction. Image Processing as Picture Analysis. The Advantages of Interactive Graphics. Representative Uses of Computer Graphics. Classification of Applications. Development of Hardware and Software for Computer Graphics. Conceptual Framework for Interactive Graphics. 2. Programming in the Simple Raster Graphics Package (SRGP)/. Drawing with SRGP/. Basic Interaction Handling/. Raster Graphics Features/. Limitations of SRGP/. 3. Basic Raster Graphics Algorithms for Drawing 2d Primitives. Overview. Scan Converting Lines. Scan Converting Circles. Scan Convertiing Ellipses. Filling Rectangles. Fillign Polygons. Filling Ellipse Arcs. Pattern Filling. Thick Primiives. Line Style and Pen Style. Clipping in a Raster World. Clipping Lines. Clipping Circles and Ellipses. Clipping Polygons. Generating Characters. SRGP_copyPixel. Antialiasing. 4. Graphics Hardware. Hardcopy Technologies. Display Technologies. Raster-Scan Display Systems. The Video Controller. Random-Scan Display Processor. Input Devices for Operator Interaction. Image Scanners. 5. Geometrical Transformations. 2D Transformations. Homogeneous Coordinates and Matrix Representation of 2D Transformations. Composition of 2D Transformations. The Window-to-Viewport Transformation. Efficiency. Matrix Representation of 3D Transformations. Composition of 3D Transformations. Transformations as a Change in Coordinate System. 6. Viewing in 3D. Projections. Specifying an Arbitrary 3D View. Examples of 3D Viewing. The Mathematics of Planar Geometric Projections. Implementing Planar Geometric Projections. Coordinate Systems. 7. Object Hierarchy and Simple PHIGS (SPHIGS). Geometric Modeling. Characteristics of Retained-Mode Graphics Packages. Defining and Displaying Structures. Modeling Transformations. Hierarchical Structure Networks. Matrix Composition in Display Traversal. Appearance-Attribute Handling in Hierarchy. Screen Updating and Rendering Modes. Structure Network Editing for Dynamic Effects. Interaction. Additional Output Features. Implementation Issues. Optimizing Display of Hierarchical Models. Limitations of Hierarchical Modeling in PHIGS. Alternative Forms of Hierarchical Modeling. 8. Input Devices, Interaction Techniques, and Interaction Tasks. Interaction Hardware. Basic Interaction Tasks. Composite Interaction Tasks. 9. Dialogue Design. The Form and Content of User-Computer Dialogues. User-Interfaces Styles. Important Design Considerations. Modes and Syntax. Visual Design. The Design Methodology. 10. User Interface Software. Basic Interaction-Handling Models. Windows-Management Systems. Output Handling in Window Systems. Input Handling in Window Systems. Interaction-Technique Toolkits. User-Interface Management Systems. 11. Representing Curves and Surfaces. Polygon Meshes. Parametric Cubic Curves. Parametric Bicubic Surfaces. Quadric Surfaces. 12. Solid Modeling. Representing Solids. Regularized Boolean Set Operations. Primitive Instancing. Sweep Representations. Boundary Representations. Spatial-Partitioning Representations. Constructive Solid Geometry. Comparison of Representations. User Interfaces for Solid Modeling. 13. Achromatic and Colored Light. Achromatic Light. Chromatic Color. Color Models for Raster Graphics. Reproducing Color. Using Color in Computer Graphics. 14. The Quest for Visual Realism. Why Realism? Fundamental Difficulties. Rendering Techniques for Line Drawings. Rendering Techniques for Shaded Images. Improved Object Models. Dynamics. Stereopsis. Improved Displays. Interacting with Our Other Senses. Aliasing and Antialiasing. 15. Visible-Surface Determination. Functions of Two Variables. Techniques for Efficient Visible-Surface Determination. Algorithms for Visible-Line Determination. The z-Buffer Algorithm. List-Priority Algorithms. Scan-Line Algorithms. Area-Subdivision Algorithms. Algorithms for Octrees. Algorithms for Curved Surfaces. Visible-Surface Ray Tracing. 16. Illumination And Shading. Illumination Modeling. Shading Models for Polygons. Surface Detail. Shadows. Transparency. Interobject Reflections. Physically Based Illumination Models. Extended Light Sources. Spectral Sampling. Improving the Camera Model. Global Illumination Algorithms. Recursive Ray Tracing. Radiosity Methods. The Rendering Pipeline. 17. Image Manipulation and Storage. What Is an Image? Filtering. Image Processing. Geometric Transformations of Images. Multipass Transformations. Image Compositing. Mechanisms for Image Storage. Special Effects with Images. Summary. 18. Advanced Raster Graphic Architecture. Simple Raster-Display System. Display-Processor Systems. Standard Graphics Pipeline. Introduction to Multiprocessing. Pipeline Front-End Architecture. Parallel Front-End Architectures. Multiprocessor Rasterization Architectures. Image-Parallel Rasterization. Object-Parallel Rasterization. Hybrid-Parallel Rasterization. Enhanced Display Capabilities. 19. Advanced Geometric and Raster Algorithms. Clipping. Scan-Converting Primitives. Antialiasing. The Special Problems of Text. Filling Algorithms. Making copyPixel Fast. The Shape Data Structure and Shape Algebra. Managing Windows with bitBlt. Page Description Languages. 20. Advanced Modeling Techniques. Extensions of Previous Techniques. Procedural Models. Fractal Models. Grammar-Based Models. Particle Systems. Volume Rendering. Physically Based Modeling. Special Models for Natural and Synthetic Objects. Automating Object Placement. 21. Animation. Conventional and Computer-Assisted Animation. Animation Languages. Methods of Controlling Animation. Basic Rules of Animation. Problems Peculiar to Animation. Appendix: Mathematics for Computer Graphics. Vector Spaces and Affine Spaces. Some Standard Constructions in Vector Spaces. Dot Products and Distances. Matrices. Linear and Affine Transformations. Eigenvalues and Eigenvectors. Newton-Raphson Iteration for Root Finding. Bibliography. Index. 0201848406T04062001

Eye-Centered Color Adaptation in Global Illumination

Color adaptation is a well known ability of the human visual system (HVS). Colors are perceived as constant even though the illuminant color changes. Indeed, the perceived color of a diffuse white sheet of paper is still white even though it is illuminated by a single orange tungsten light, whereas it is orange from a physical point of view. Unfortunately global illumination algorithms only focus on the physics aspects of light transport. The ouput of a global illuminantion engine is an image which has to undergo chromatic adaptation to recover the color as perceived by the HVS. In this paper, we propose a new color adaptation method well suited to global illumination. This method estimates the adaptation color by averaging the irradiance color arriving at the eye. Unlike other existing methods, our approach is not limited to the view frustrum, as it considers the illumination from all the scene. Experiments have shown that our method outperforms the state of the art methods.

Factorized Point Based Global Illumination

AbstractThe 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.