A survey of techniques and technologies for web-based real-time interactive rendering

When exploring a virtual environment, realism depends mainly on two factors: realistic images and real-time feedback (motions, behaviour etc.). In this context, photo realism and physical validity of computer generated images required by emerging applications, such as advanced e-commerce, still impose major challenges in the area of rendering research whereas the complexity of lighting phenomena further requires powerful and predictable computing if time constraints must be attained. In this technical report we address the state-of-the-art on rendering, trying to put the focus on approaches, techniques and technologies that might enable real-time interactive web-based clientserver rendering systems. The focus is on the end-systems and not the networking technologies used to interconnect client(s) and server(s).Siemens; Bertelsmann mediaSystems GmbH; Eptron Multimedia; Instituto Politécnico do Porto - ISEP-IPP; Institute Laboratory for Mixed Realities at the Academy of Media Arts Cologne, LMR; Mälardalen Real-Time Research Centre (MRTC) at Mälardalen University in Västerås; Q-Systems

GPGPU computation and visualization of three-dimensional cellular automata

This paper presents a general-purpose simulation approach integrating a set of technological developments and algorithmic methods in cellular automata (CA) domain. The approach provides a general-purpose computing on graphics processor units (GPGPU) implementation for computing and multiple rendering of any direct-neighbor three-dimensional (3D) CA. The major contributions of this paper are: the CA processing and the visualization of large 3D matrices computed in real time; the proposal of an original method to encode and transmit large CA functions to the graphics processor units in real time; and clarification of the notion of top-down and bottom-up approaches to CA that non-CA experts often confuse. Additionally a practical technique to simplify the finding of CA functions is implemented using a 3D symmetric configuration on an interactive user interface with simultaneous inside and surface visualizations. The interactive user interface allows for testing the system with different project ideas and serves as a test bed for performance evaluation. To illustrate the flexibility of the proposed method, visual outputs from diverse areas are demonstrated. Computational performance data are also provided to demonstrate the method’s efficiency. Results indicate that when large matrices are processed, computations using GPU are two to three hundred times faster than the identical algorithms using CPU

Volume MLS Ray Casting

The method of Moving Least Squares (MLS) is a popular framework for reconstructing continuous functions from scattered data due to its rich mathematical properties and well-understood theoretical foundations. This paper applies MLS to volume rendering, providing a unified mathematical framework for ray casting of scalar data stored over regular as well as irregular grids. We use the MLS reconstruction to render smooth isosurfaces and to compute accurate derivatives for high-quality shading effects. We also present a novel, adaptive preintegration scheme to improve the efficiency of the ray casting algorithm by reducing the overall number of function evaluations, and an efficient implementation of our framework exploiting modern graphics hardware. The resulting system enables high-quality volume integration and shaded isosurface rendering for regular and irregular volume data.Engineering and Applied Science

Mental vision:a computer graphics platform for virtual reality, science and education

Despite the wide amount of computer graphics frameworks and solutions available for virtual reality, it is still difficult to find a perfect one fitting at the same time the many constraints of research and educational contexts. Advanced functionalities and user-friendliness, rendering speed and portability, or scalability and image quality are opposite characteristics rarely found into a same approach. Furthermore, fruition of virtual reality specific devices like CAVEs or wearable systems is limited by their costs and accessibility, being most of these innovations reserved to institutions and specialists able to afford and manage them through strong background knowledge in programming. Finally, computer graphics and virtual reality are a complex and difficult matter to learn, due to the heterogeneity of notions a developer needs to practice with before attempting to implement a full virtual environment. In this thesis we describe our contributions to these topics, assembled in what we called the Mental Vision platform. Mental Vision is a framework composed of three main entities. First, a teaching/research oriented graphics engine, simplifying access to 2D/3D real-time rendering on mobile devices, personal computers and CAVE systems. Second, a series of pedagogical modules to introduce and practice computer graphics and virtual reality techniques. Third, two advanced VR systems: a wearable, lightweight and handsfree mixed reality setup, and a four sides CAVE designed through off the shelf hardware. In this dissertation we explain our conceptual, architectural and technical approach, pointing out how we managed to create a robust and coherent solution reducing complexity related to cross-platform and multi-device 3D rendering, and answering simultaneously to contradictory common needs of computer graphics and virtual reality for researchers and students. A series of case studies evaluates how Mental Vision concretely satisfies these needs and achieves its goals on in vitro benchmarks and in vivo scientific and educational projects

Analysis of the Path Tracing rendering method on CPU and GPU

Fa molts anys que es realitza recerca al camp de la renderització realista. Tenim diversos mètodes capaços d'aconseguir imatges amb un gran grau de realisme, com pot ser Ray Tracing, Path Tracing, Photon Mapping o Metropolis Light Transport. A excepció del Ray Tracing, la resta de mètodes tracten de resoldre l'Equació de Renderitzat mitjançant aproximacions (és impossible calcular-la íntegrament, ja que necessitaríem temps i potència de càlcul infinita). Gràcies a poder aproximar aquesta equació es poden aconseguir efectes de forma natural, sense necessitat d'un postprocessat, com motion blur, depth of field, càustiques, etc. El mètode que implementarem i estudiarem és el Path Tracing. Realitzarem diverses versions d'aquest mètode amb les quals podrem explorar quina arquitectura (GPU o CPU) ens ofereix una major avantatge pel que fa al rendiment per al nostre algoritme. Per això comptarem amb diverses màquines, una amb un hardware d'última generació, una amb un hardware més econòmic i una última màquina pensada per un entorn professional. És molt usual que les aplicacions que implementen aquest mètode s'utilitzen d'estructures de dades que permeten millorar de forma molt notable el rendiment d'aquesta. Per aquesta raó, implementarem una Bounding Volume Hierarchy, un estructura de tipus arbre, per a la representació de l'escena i així augmentar el rendiment. Estudiarem com recorre-la de dues formes diferents, una recursiva molt més natural en aquest tipus d'estructures i un altre iterativa, per veure com afecta al rendiment de l'aplicació en la GPU. És ben sabut que les funcions recursives no són gens òptimes a la GPU. Per últim, implementarem un seguit de filtres d'eliminació de soroll. El mètode de Path Tracing produeix imatges molt sorolloses si s'utilitzen poques mostres per píxel, per això l'ús de filtres d'eliminació de soroll és molt comú. Això ens permetrà trobar un equilibri entre el nombre de mostres per píxel i la necessitat d'un postfiltratge de la imatge resultant.The field of realistic rendering has been investigated for many years. We have different methods capable of creating images with a high degree of realism, such as Ray Tracing, Path Tracing, Photon Mapping or Metropolis Light Transport. Except for Ray Tracing, the rest of the cited methods try to solve the Rendering Equation by approximations (it is impossible to calculate it completely because we would need time and infinite computing power). Thanks to being able to approximate this equation, effects can be achieved naturally, without needing any post-processing, such as motion blur, depth of field, caustics, etc. The method that we will implement and study is Path Tracing. We will make several versions of this method with which we will explore which architecture (GPU or CPU) gives us a greater advantage in terms of performance for our algorithm. For this, we will have different machines, one with the last generation hardware, one with cheaper hardware and the last machine with hardware thought for a professional environment. It is very usual that the applications that implement this method are assisted by accelerating structures that allow improving in a very notable way the performance of this one. For this same reason, we will implement a Bounding Volume Hierarchy, a tree-type structure, to represent our scene and thus increase performance. We will study how to go through it in two different ways, one recursive much more natural in this type of structure and another iterative, to see how it affects the performance of the application on the GPU. It's well known that the GPU is not optimal for recursive functions. Finally, we'll implement a set of denoising filters. Path tracing produces very noisy images when using a few samples per pixel, so the use of denoising filters is very common. This will also help us find a balance between the number of samples per pixel and the need for post-filtering of the output image

Time-varying volume visualization

Volume rendering is a very active research field in Computer Graphics because of its wide range of applications in various sciences, from medicine to flow mechanics. In this report, we survey a state-of-the-art on time-varying volume rendering. We state several basic concepts and then we establish several criteria to classify the studied works: IVR versus DVR, 4D versus 3D+time, compression techniques, involved architectures, use of parallelism and image-space versus object-space coherence. We also address other related problems as transfer functions and 2D cross-sections computation of time-varying volume data. All the papers reviewed are classified into several tables based on the mentioned classification and, finally, several conclusions are presented.Preprin

Real-time voxel rendering algorithm based on screen space billboard voxel buffer with sparse lookup textures

In this paper, we present a novel approach to efficient real-time rendering of numerous high-resolution voxelized objects. We present a voxel rendering algorithm based on triangle rasterization pipeline with screen space rendering computational complexity. In order to limit the number of vertex shader invocations, voxel filtering algorithm with fixed size voxel data buffer was developed. Voxelized objects are represented by sparse voxel octree (SVO) structure. Using sparse texture available in modern graphics APIs, we create a 3D lookup table for voxel ids. Voxel filtering algorithm is based on 3D sparse texture ray marching approach. Screen Space Billboard Voxel Buffer is filled by voxels from visible voxels point cloud. Thanks to using 3D sparse textures, we are able to store high-resolution objects in VRAM memory. Moreover, sparse texture mipmaps can be used to control object level of detail (LOD). The geometry of a voxelized object is represented by a collection of points extracted from object SVO. Each point is defined by position, normal vector and texture coordinates. We also show how to take advantage of programmable geometry shaders in order to store voxel objects with extremely low memory requirements and to perform real-time visualization. Moreover, geometry shaders are used to generate billboard quads from the point cloud and to perform fast face culling. As a result, we obtained comparable or even better performance results in comparison to SVO ray tracing approach. The number of rendered voxels is limited to defined Screen Space Billboard Voxel Buffer resolution. Last but not least, thanks to graphics card adapter support, developed algorithm can be easily integrated with any graphics engine using triangle rasterization pipeline

GPGPU computation and visualization of three-dimensional cellular automata

This paper presents a general-purpose simulation approach integrating a set of technological developments and algorithmic methods in cellular automata (CA) domain. The approach provides a general-purpose computing on graphics processor units (GPGPU) implementation for computing and multiple rendering of any direct-neighbor three-dimensional (3D) CA. The major contributions of this paper are: the CA processing and the visualization of large 3D matrices computed in real time; the proposal of an original method to encode and transmit large CA functions to the graphics processor units in real time; and clarification of the notion of top-down and bottom-up approaches to CA that non-CA experts often confuse. Additionally a practical technique to simplify the finding of CA functions is implemented using a 3D symmetric configuration on an interactive user interface with simultaneous inside and surface visualizations. The interactive user interface allows for testing the system with different project ideas and serves as a test bed for performance evaluation. To illustrate the flexibility of the proposed method, visual outputs from diverse areas are demonstrated. Computational performance data are also provided to demonstrate the method's efficiency. Results indicate that when large matrices are processed, computations using GPU are two to three hundred times faster than the identical algorithms using CP