Immersive front-projection analysis using a radiosity-based simulation method

International audienceVideo projectors are designed to project onto flat white diffuse screens. Over the last few years, projector-based systems have been used, in virtual reality applications, to light non-specific environments such as the walls of a room. However, in these situations, the images seen by the user are affected by several radiometric disturbances, such as interreflection. Radiometric compensa tion methods have been proposed to reduce the disturbance caused by interreflection, but nothing has been proposed for evaluating the phenomenon itself and the effectiveness of compensation methods. In this paper, we propose a radiosity-based method to simulate light transfer in immersive environments, from a projector to a camera (the camera gives the image a user would see in a real room). This enables us to evaluate the disturbances resulting from interreflection. We also consider the effectiveness of interreflection compensation and study the influence of several parameters (projected image, projection onto a small or large part of the room, reflectivity of the walls). Our results show that radiometric compensation can reduce the influence of interreflection but is severely limited if we project onto a large part of the walls around the user, or if all the walls are bright

Virtual reality as an educational tool in interior architecture

Ankara : The Department of Interior Architecture and Environmental Design and the Institute of Fine Arts of Bilkent Univ., 1997.Thesis (Master's) -- Bilkent University, 1997.Includes bibliographical references.This thesis discusses the use of virtual reality technology as an educational tool in interior architectural design. As a result of this discussion, it is proposed that virtual reality can be of use in aiding three-dimensional design and visualization, and may speed up the design process. It may also be of help in getting the designers/students more involved in their design projects. Virtual reality can enhance the capacity of designers to design in three dimensions. The virtual reality environment used in designing should be capable of aiding both the design and the presentation process. The tradeoffs of the technology, newly emerging trends and future directions in virtual reality are discussed.Aktaş, OrkunM.S

Defining Reality in Virtual Reality: Exploring Visual Appearance and Spatial Experience Focusing on Colour

Today, different actors in the design process have communication difficulties in visualizing and predictinghow the not yet built environment will be experienced. Visually believable virtual environments (VEs) can make it easier for architects, users and clients to participate in the planning process. This thesis deals with the difficulties of translating reality into digital counterparts, focusing on visual appearance(particularly colour) and spatial experience. The goal is to develop knowledge of how differentaspects of a VE, especially light and colour, affect the spatial experience; and thus to contribute to a better understanding of the prerequisites for visualizing believable spatial VR-models. The main aims are to 1) identify problems and test solutions for simulating realistic spatial colour and light in VR; and 2) develop knowledge of the spatial conditions in VR required to convey believable experiences; and evaluate different ways of visualizing spatial experiences. The studies are conducted from an architecturalperspective; i.e. the whole of the spatial settings is considered, which is a complex task. One important contribution therefore concerns the methodology. Different approaches were used: 1) a literature review of relevant research areas; 2) a comparison between existing studies on colour appearance in 2D vs 3D; 3) a comparison between a real room and different VR-simulations; 4) elaborationswith an algorithm for colour correction; 5) reflections in action on a demonstrator for correct appearance and experience; and 6) an evaluation of texture-styles with non-photorealistic expressions. The results showed various problems related to the translation and comparison of reality to VR. The studies pointed out the significance of inter-reflections; colour variations; perceived colour of light and shadowing for the visual appearance in real rooms. Some differences in VR were connected to arbitrary parameter settings in the software; heavily simplified chromatic information on illumination; and incorrectinter-reflections. The models were experienced differently depending on the application. Various spatial differences between reality and VR could be solved by visual compensation. The study with texture-styles pointed out the significance of varying visual expressions in VR-models

Defining Reality in Virtual Reality: Exploring Visual Appearance and Spatial Experience Focusing on Colour

Today, different actors in the design process have communication difficulties in visualizing and predictinghow the not yet built environment will be experienced. Visually believable virtual environments (VEs) can make it easier for architects, users and clients to participate in the planning process. This thesis deals with the difficulties of translating reality into digital counterparts, focusing on visual appearance(particularly colour) and spatial experience. The goal is to develop knowledge of how differentaspects of a VE, especially light and colour, affect the spatial experience; and thus to contribute to a better understanding of the prerequisites for visualizing believable spatial VR-models. The main aims are to 1) identify problems and test solutions for simulating realistic spatial colour and light in VR; and 2) develop knowledge of the spatial conditions in VR required to convey believable experiences; and evaluate different ways of visualizing spatial experiences. The studies are conducted from an architecturalperspective; i.e. the whole of the spatial settings is considered, which is a complex task. One important contribution therefore concerns the methodology. Different approaches were used: 1) a literature review of relevant research areas; 2) a comparison between existing studies on colour appearance in 2D vs 3D; 3) a comparison between a real room and different VR-simulations; 4) elaborationswith an algorithm for colour correction; 5) reflections in action on a demonstrator for correct appearance and experience; and 6) an evaluation of texture-styles with non-photorealistic expressions. The results showed various problems related to the translation and comparison of reality to VR. The studies pointed out the significance of inter-reflections; colour variations; perceived colour of light and shadowing for the visual appearance in real rooms. Some differences in VR were connected to arbitrary parameter settings in the software; heavily simplified chromatic information on illumination; and incorrectinter-reflections. The models were experienced differently depending on the application. Various spatial differences between reality and VR could be solved by visual compensation. The study with texture-styles pointed out the significance of varying visual expressions in VR-models

Audio-visual Virtual Reality System for Room Acoustics

We present an audio-visual Virtual Reality display system for simulated sound fields. In addition to the room acoustic simulation by means of phonon tracing and finite element method this system includes the stereoscopic visualization of simulation results using a 3D back projection system as well as auralization by use of a professional sound equipment. For auralization purposes we develop a sound field synthesis approach for accurate control of the loudspeaker system

Virtual light fields for global illumination in computer graphics

This thesis presents novel techniques for the generation and real-time rendering of globally illuminated environments with surfaces described by arbitrary materials. Real-time rendering of globally illuminated virtual environments has for a long time been an elusive goal. Many techniques have been developed which can compute still images with full global illumination and this is still an area of active flourishing research. Other techniques have only dealt with certain aspects of global illumination in order to speed up computation and thus rendering. These include radiosity, ray-tracing and hybrid methods. Radiosity due to its view independent nature can easily be rendered in real-time after pre-computing and storing the energy equilibrium. Ray-tracing however is view-dependent and requires substantial computational resources in order to run in real-time. Attempts at providing full global illumination at interactive rates include caching methods, fast rendering from photon maps, light fields, brute force ray-tracing and GPU accelerated methods. Currently, these methods either only apply to special cases, are incomplete exhibiting poor image quality and/or scale badly such that only modest scenes can be rendered in real-time with current hardware. The techniques developed in this thesis extend upon earlier research and provide a novel, comprehensive framework for storing global illumination in a data structure - the Virtual Light Field - that is suitable for real-time rendering. The techniques trade off rapid rendering for memory usage and precompute time. The main weaknesses of the VLF method are targeted in this thesis. It is the expensive pre-compute stage with best-case O(N^2) performance, where N is the number of faces, which make the light propagation unpractical for all but simple scenes. This is analysed and greatly superior alternatives are presented and evaluated in terms of efficiency and error. Several orders of magnitude improvement in computational efficiency is achieved over the original VLF method. A novel propagation algorithm running entirely on the Graphics Processing Unit (GPU) is presented. It is incremental in that it can resolve visibility along a set of parallel rays in O(N) time and can produce a virtual light field for a moderately complex scene (tens of thousands of faces), with complex illumination stored in millions of elements, in minutes and for simple scenes in seconds. It is approximate but gracefully converges to a correct solution; a linear increase in resolution results in a linear increase in computation time. Finally a GPU rendering technique is presented which can render from Virtual Light Fields at real-time frame rates in high resolution VR presentation devices such as the CAVETM

Development of Suntool prototype for sunlight/shadow study in architecture immersive visualization

Master'sMASTER OF ARTS (ARCHITECTURE

The Plausibility of a String Quartet Performance in Virtual Reality

We describe an experiment that explores the contribution of auditory and other features to the illusion of plausibility in a virtual environment that depicts the performance of a string quartet. ‘Plausibility’ refers to the component of presence that is the illusion that the perceived events in the virtual environment are really happening. The features studied were: Gaze (the musicians ignored the participant, the musicians sometimes looked towards and followed the participant’s movements), Sound Spatialization (Mono, Stereo, Spatial), Auralization (no sound reflections, reflections corresponding to a room larger than the one perceived, reflections that exactly matched the virtual room), and Environment (no sound from outside of the room, birdsong and wind corresponding to the outside scene). We adopted the methodology based on color matching theory, where 20 participants were first able to assess their feeling of plausibility in the environment with each of the four features at their highest setting. Then five times participants started from a low setting on all features and were able to make transitions from one system configuration to another until they matched their original feeling of plausibility. From these transitions a Markov transition matrix was constructed, and also probabilities of a match conditional on feature configuration. The results show that Environment and Gaze were individually the most important factors influencing the level of plausibility. The highest probability transitions were to improve Environment and Gaze, and then Auralization and Spatialization. We present this work as both a contribution to the methodology of assessing presence without questionnaires, and showing how various aspects of a musical performance can influence plausibility

A graphics processing unit based method for dynamic real-time global illumination

Real-time realistic image synthesis for virtual environments has been one of the most actively researched areas in computer graphics for over a decade. Images that display physically correct illumination of an environment can be simulated by evaluating a multi-dimensional integral equation, called the rendering equation, over the surfaces of the environment. Many global illumination algorithms such as pathtracing, photon mapping and distributed ray-tracing can produce realistic images but are generally unable to cope with dynamic lighting and objects at interactive rates. It still remains one of most challenging problems to simulate physically correctly illuminated dynamic environments without a substantial preprocessing step. In this thesis we present a rendering system for dynamic environments by implementing a customized rasterizer for global illumination entirely on the graphics hardware, the Graphical Processing Unit. Our research focuses on a parameterization of discrete visibility field for efficient indirect illumination computation. In order to generate the visibility field, we propose a CUDA-based (Compute Unified Device Architecture) rasterizer which builds Layered Hit Buffers (LHB) by rasterizing polygons into multi-layered structural buffers in parallel. The LHB provides a fast visibility function for any direction at any point. We propose a cone approximation solution to resolve an aliasing problem due to limited directional discretization. We also demonstrate how to remove structure noises by adapting an interleaved sampling scheme and discontinuity buffer. We show that a gathering method amortized with a multi-level Quasi Mont Carlo method can evaluate the rendering equation in real-time. The method can realize real-time walk-through of a complex virtual environment that has a mixture of diffuse and glossy reflection, computing multiple indirect bounces on the fly. We show that our method is capable of simulating fully dynamic environments including changes of view, materials, lighting and objects at interactive rates on commodity level graphics hardware

Virtual reality for the built environment: A critical review of recent advances

This paper reviews the current state of the art for Virtual Reality (VR) and Virtual Environment (VE) applications in the field of the built environment. The review begins with a brief overview of technological components involved in enabling VR technology. A classification framework is developed to classify 150 journal papers in order to reveal the scholarly coverage of VR and VE from 2005 to 2011, inclusive. The classification framework summarizes achievements, established knowledge, research issues and challenges in the area. The framework is based on four layers of VR: concept and theory, implementation, evaluation and industrial adoption. These layers encompass architecture and design, urban planning and landscape, engineering, construction, facility management, lifecycle integration, training and education. This paper also discusses various representative VR research work in line with the classification framework. Finally the paper predicts future research trends in this area