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An Object-oriented Methodology with Dynamic Variables for Animation and Scientific Visualization
(Springer, 1990) Turner, Russell; Gobbetti, Enrico; Balaguer, Jean-Francis; Mangili, Angelo; Thalmann, Daniel
An object-oriented design is presented for building dynamic three-dimensional applications. This design takes the form of the Fifth Dimension Toolkit consisting of a set of interrelated classes whose instances may be connected together in a variety of ways to form different applications. Animation is obtained by connecting graphical objects to dynamic variables, which are able to change their values over time by responding to events. The Fifth Dimension Toolkit is the core of the Fifth Dimension Project, a research project for animating synthetic actors in their environment. The design philosophy and methodology of the toolkit are also described, as well as some of the implementation issues for the Silicon Graphics Iris 4D workstation.
Interactive Scene Walkthrough Using a Physically-Based Virtual Camera
(Vieweg, 1991) Turner, Russell; Balaguer, Jean-Francis; Gobbetti, Enrico; Thalmann, Daniel
One of the most powerful results of recent advances in graphics hardware is the ability of a computer user to interactively explore a virtual buildin gor landscape. The newest three-dimensional input devices, together with high speed {3D} graphics workstations, make it possible to view and move through a {3D} scene by interactively controlling the motion of a virtual camera. In this paper, we describe how natural and intuitive control of building walkthrough can be achieved by using a physically-based model of the virtual camera's behavior. Using the laws of classical mechanics to create and abstract physical model of the camera, we then simulate the virtual camera motion in real time in response to force date from the various {3D} input devices (e.g. the Spaceball and Polhemus 3Space Digitizer). The resulting interactive behavior of the model is determined by several physical parameters such as mass, moment of inertia, and various friction coefficients which can all be varied interactively, and by constraints on the camera's degrees of freedom. This allows us to explore a continuous range of physically-based metaphors for controlling the camera motion. We present the results of experiments using several of these metaphors for virtual camera motion and describe the effects of the various physical parameters.
Physically-based interactive camera motion control using 3D input devices
(Springer, 1991) Turner, Russell; Balaguer, Jean-Francis; Gobbetti, Enrico; Thalmann, Daniel
The newest three-dimensional input devices, together with high speed graphics workstations, make it possible to interactively specify virtual camera motions for animation in real time. In this paper, we describe how naturalistic interaction and realistic-looking motion can be achieved by using a physically-based model of the camera's behavior. Our approach is to create an abstract physical model of the camera, using the laws of classical mechanics, which is used to simulate the virtual camera motion in real time in response to force data from the various 3D input devices (e.g. the Spaceball, Polhemus and DataGlove). The behavior of the model is determined by several physical parameters such as mass, moment of inertia, and various friction coefficients which can all be varied interactively, and by constraints on the camera's degrees of freedom which can be simulated by setting certain friction parameters to very high values. This allows us to explore a continuous range of physically-based metaphors for controlling the camera motion. We present the results of experiments with several of these metaphors and contrast them with existing ones.
Object-oriented design of dynamic graphics applications
(Wiley, 1992) Gobbetti, Enrico; Turner, Russell
VB2: an architecture for interaction in synthetic worlds
(ACM, 1993) Gobbetti, Enrico; Balaguer, Jean-Francis
This paper describes the VB2 architecture for the construction of three-dimensional interactive applications. The system's state and behavior are uniformly represented as a network of interrelated objects. Dynamic components are modeled by active variables, while multi-way relations are modeled by hierarchical constraints. Daemons are used to sequence between system states in reaction to changes in variable values. The constraint network is efficiently maintained by an incremental constraint solver based on an enhancement of SkyBlue. Multiple devices are used to interact with the synthetic world through the use of various interaction paradigms, including immersive environments with visual and audio feedback. Interaction techniques range from direct manipulation, to gestural input and three-dimensional virtual tools. Adaptive pattern recognition is used to increase input device expressiveness by enhancing sensor data with classification information. Virtual tools, which are encapsulations of visual appearance and behavior, present a selective view of manipulated models' information and offer an interaction metaphor to control it. Since virtual tools are first class objects, they can be assembled into more complex tools, much in the same way that simple tools are built on top of a modeling hierarchy. The architecture is currently being used to build a virtual reality animation system.
Virtuality Builder II: on the topic of 3D interaction
(1993) Gobbetti, Enrico; Balaguer, Jean-Francis
Most of today's user interfaces for 3D graphics systems still predominantly use 2D widgets, even though current graphical hardware should make it possible to create applications in which the user directly manipulates aspects of three-dimensional synthetic worlds. The difficulties associated with achieving the key goal of immersion has led the research in virtual environments to concentrate far more on the development of new input and display devices than on higher-level techniques for 3D interaction. It is only recently that interaction with synthetic worlds has tried to go beyond straightforward interpretation of physical device data. The design space for 3D interaction tools and techniques remains mostly unexplored, while being far larger than in standard 2D applications. Moreover, as stated by Myers, "the only reliable way to generate quality interfaces is to test prototypes with users and modify the design based on their comments". The creation of complex interactive applications is an inherently iterative process that requires user interface tools, such as toolkits or frameworks. The lack of experience in 3D interfaces makes it extremely difficult to design 3D interface toolkits or frameworks. We believe that offering the possibility to rapidly prototype and test novel interaction techniques should be the primary goal of such tools. It is therefore more important for these tools to provide a wide range of interaction components, than to enforce a particular interface style. In this paper we present the Virtuality Builder II (VB2) framework developed at the Swiss Federal Institute of Technology for the construction of 3D interactive applications. First, we'll give an overview of the design concepts of VB2. Next, we'll concentrate on how users interact with dynamic models through direct manipulation, gestures, and virtual tools.
Building an interactive 3D animation system
(Prentice Hall, 1993) Gobbetti, Enrico; Balaguer, Jean-Francis; Mangili, Angelo; Turner, Russell
The continued improvement and proliferation of graphics hardware for workstations and personal computers has brought increasing prominence to a newer style of software application program. This style relies on fast, high quality graphics displays coupled with expressive input devices to achieve real-time animation and direct-manipulation interaction metaphors. Such applications impose a rather different conceptual approach, on both the user and the programmer, than more traditional software. The application program can be thought of increasingly as a virtual machine, with a tangible two or three dimensional appearance, behavior and tactile response. Dynamic graphics techniques are now considered essential for making computers easier to use, and interactive and graphical interfaces that allow the presentation and the direct manipulation of information in a pictorial form is now an important part of most of modern graphics software tools
A multimedia testbed for facial animation control
(World Scientific, 1993-11) Kalra, Prem; Gobbetti, Enrico; Magnenat-Thalmann, Nadia; Thalmann, Daniel
This paper presents an open testbed for controlling facial animation. The adopted controlling means can act at different levels of abstraction (specification). These means of control can be associated with different interactive devices and media thereby allowing a greater flexibility and freedom to the animator. Possibility of integration and mixing of control means provides a general platform where a user can experiment with his choice of control method. Experiments with input accessories like the keyboard of a music sinthesizer and gestures from the DataGlove are illustrated.
Virtual sardinia: a hypermedia fly-through with real data
(1995) Gobbetti, Enrico; Leone, Andrea O.; Marini, Alberto
The Virtual Sardinia project aims at collecting a large amount of heterogeneous data concerning the island of Sardinia and representing them in such a way that a casual user can easily navigate through them in a virtual trip. All these data are interconnected in an hypermedia way, browsable in the World-wide Web, ranging from geographic to archaeological data, from historical to touristical info, both in 2D and 3D. The central component of Virtual Sardinia is i3D, a high-speed 3D scene viewer for the World-wide Web. Using a Spaceball, the user can intuitively navigate with continuous viewpoint control inside three-dimensional data, while selecting 3D objects with the mouse triggers requests for access to remote media documents that can be distributed over the Internet. For the Virtual Sardinia project, the main 3D model that is explored by the users is a three-dimensional reconstruction of the island of Sardinia built from a digital terrain model texture-mapped with satellite images.
i3D: a high-speed 3D Web browser
(ACM, 1995) Balaguer, Jean-Francis; Gobbetti, Enrico
In this paper, we present i3D, a system that combines the 3D input and high-performance rendering capabilities of high-end virtual reality systems with the data fetching abilities of network browsers. Using a Spaceball, the user can intuitively navigate inside the three-dimensional data, while selecting 3D objects with the mouse triggers requests for access to remote media documents that can be text, still images, animations or even other 3D models. Time-critical rendering techniques allow the system to display complex 3D scenes at high and constant frame rates, making it possible to use it in the context of large scale projects. The system is currently being used at CERN as a visualization and data management tool for the design of the new Large Hadron Collider, and at CRS4 for the Virtual Sardinia project and in the networked educational system IPERLER. i3D is available through anonymous ftp from various sites on the Internet.
An Integrated Environment to Visually Construct 3D Animations
(ACM, 1995) Gobbetti, Enrico; Balaguer, Jean-Francis
In this paper, we present an expressive 3D animation environment that enables users to rapidly and visually prototype animated worlds with a fully 3D user-interface. A 3D device allows the specification of complex 3D motion, while virtual tools are visible mediators that live in the same 3D space as application objects and supply the interaction metaphors to control them. In our environment, there is no intrinsic difference between user-interface and application objects. Multi-way constraints provide the necessary tight-coupling among components that makes it possible to seamlessly compose interactive and animated behaviors. By recording the effects of manipulations, all the expressive power of the 3D user-interface is exploited to define animations. Effective editing of recorded manipulations is made possible by compacting all continuous parameter evolutions with an incremental data-reduction algorithm, designed to preserve both geometry and timing. The automatic generation of editable representations of interactive performances overcomes one of the major limitations of current performance animation systems. Novel interactive solutions to animation problems are made possible by the tight integration of all system components. In particular, animations can be synchronized by using constrained manipulation during playback. The accompanying video tape illustrates our approach with interactive sequences showing the visual construction of 3D animated worlds. All the demonstrations were recorded live and were not edited.
Supporting interactive animation using multi-way constraints
(Springer, 1995) Balaguer, Jean-Francis; Gobbetti, Enrico
This paper presents how the animation subsystem of an interactive environment for the visual construction of 3D animations has been modeled on top of an object-oriented constraint imperative architecture. In our architecture, there is no intrinsic difference between user-interface and application objects. Multi-way dataflow constraints provide the necessary tight coupling among components that makes it possible to seamlessly compose animated and interactive behaviors. Indirect paths allow an effective use of the constraint model in the context of dynamic applications. The ability of the underlying constraint solver to deal with hierarchies of multi-way, multi-output dataflow constraints, together with the ability of the central state manager to handle indirect constraints are exploited to define most of the behaviors of the modeling and animation components in a declarative way. The ease of integration between all system's components opens the door to novel interactive solution to modeling and animation problems. By recording the effects of the user's manipulations on the models, all the expressive power of the 3D user interface is exploited when defining animations. This performance-based approach complements standard key-framing systems by providing the ability to create animations with straight-ahead actions. At the end of the recording session, animation tracks are automatically updated to integrate the new piece of animation. Animation components can be easily synchronized using constrained manipulation during playback. The system demonstrates that, although they are limited to expressing acyclic conflict-free graphs, multi-way dataflow constraint are general enough to model a large variety of behaviors while remaining efficient enough to ensure the responsiveness of large interactive 3D graphics applications.
i3D: an interactive system for exploring annotated 3D environments
(World Scientific, 1995-08) Gobbetti, Enrico; Balaguer, Jean-Francis
In this paper, we present I3D, a system that combines the 3D input and high-performance rendering capabilities of high-end virtual reality systems with the data fetching abilities of network browsers. Using a Spaceball, the user can intuitively navigate inside the three-dimensional data, while selecting 3D objects with the mouse triggers requests for access to remote media documents that can be text, still images, animations or even other 3D models. Time-critical rendering techniques allow the system to display complex 3D scenes at high and constant frame rates, making it possible to use it in the context of large scale projects. The system is currently being used at CERN as a visualization and data management tool for the design of the new Large Hadron Collider, and will be used at CRS4 in the networked educational system IPERLER.
Exploring annotated 3D environments on the world-wide web
(Springer, 1997) Gobbetti, Enrico; Turner, Russell
The long-term goal of combining virtual reality and the Internet is to create networked multi-user simulations of virtual environments. The Virtual Reality Modeling Language (VRML) represents a limited but significant step towards this goal by creating a standard data file format for representing 3D scene information, together with hyper-link information for associating it with other types of Web documents. Current proposals for extending VRML-1.0 to add behaviors will bring this goal closer, but much work remains to be done. This chapter gives a brief summary of VRML and then describes two significant projects currently under development based on i3D, a high-performance VRML browser developed by one of the authors. The first of these, currently being used at the European Laboratory for Particle Physics (CERN), uses an annotated virtual environment to visualize and walk through the physical design of the new Lepton-Hadron Collider (LHC) before it is built. The second project, Virtual Sardinia, allows the user to tour a 3D terrain visualization of the island and access historic and tourist information through hyper-links.
3D spectral reverse time migration with no-wraparound absorbing conditions
(SEG, 1998) Bonomi, Ernesto; Brieger, Leesa; Nardone, Carlo; Pieroni, Enrico
Comparative studies of methods of reverse time migration (RTM) show that spectral methods for calculating the Laplacian impose the least stringent demands on discretization stepsize; thus with spectral methods, the grid refinements often required by other methods can be avoided. Implemented with absorbing boundary conditions, which are energy-tuned to give good absorption at the boundaries, these spectral methods can be used effectively for migration, without suffering the problems of wraparound which have traditionally plagued them (Furumyra and Takenaka, 1995).
Discontinuous finite element visualization
(1998-09) Leone, Andrea O.; Marzano, Paola; Gobbetti, Enrico; Scateni, Riccardo; Pedinotti, Sergio
The aim of this work is the study and the implementation of appropriate visualization techniques for high-order discontinuous finite element data in two and three-dimensions. In particular, we are dealing with field discontinuity and deformed cells. Such data are produced for example by chemical simulations, by fluid dynamics simulations, or, in general, anywhere high accuracy on boundary domain description is required.
Interactive virtual angioscopy
(IEEE, 1998-10) Gobbetti, Enrico; Pili, Piero; Zorcolo, Antonio; Tuveri, Massimiliano
Virtual angioscopy is a non invasive medical procedure for exploring parts of the human vascular system. We have developed an interactive tool that takes as input data acquired with standard medical imaging modalities and regards it as a virtual environment to be interactively inspected. The system supports real-time navigation with stereoscopic direct volume rendering and dynamic endoscopic camera control, interactive tissue classification, and interactive point picking for morphological feature measurement. In this paper, we provide an overview of the system, discuss the techniques used in our prototype, and present experimental results on human data sets. The accompanying video-tape illustrates our approach with interactive sequences showing the examination of a human carotid artery.
Virtual reality: past, present, and future
(IOS, 1998-11) Gobbetti, Enrico; Scateni, Riccardo
This report provides a short survey of the field of virtual reality, highlighting application domains, technological requirements, and currently available solutions. The report is organized as follows: section 1 presents the background and motivation of virtual environment research and identifies typical application domains, section 2 discusses the characteristics a virtual reality system must have in order to exploit the perceptual and spatial skills of users, section 3 surveys current input/output devices for virtual reality, section 4 surveys current software approaches to support the creation of virtual reality systems, and section 5 summarizes the report.
Coupled surface runoff and subsurface flow model for catchment simulations
(Wageningen Press, 1999) Bixio, Anna Chiara; Orlandini, Stefano; Paniconi, Claudio; Putti, Mario
A distributed catchment scale numerical model for the simulation of coupled surface runoff and subsurface flow is presented. Starting from rainfall (evaporation) records, the model first determines the infiltration (exfiltration) rates in the soil, by evaluation of the soil field capacity at the specific conditions as calculated from the three-dimensional solution of the variably-saturated groundwater flow model (Richards’ equation). The flow rate that remains or returns to the surface, the so called overland flow, is then routed via a diffusion wave surface runoff model based on a Muskingum-Cunge scheme with variable parameters. Both hillslope and channel flow are described, and a special algorithm is used for the simulation of pools/lakes effects on storm-flow response. The importance of including detailed subsurface flow description in catchment simulations is shown on a simple testcase characterized by the presence of a central depression.
Three-dimensional graphics
(Wiley, 1999-02) Gobbetti, Enrico; Scateni, Riccardo
Three-dimensional graphics is the area of computer graphics that deals with producing two-dimensional representations, or images, of three-dimensional synthetic scenes, as seen from a given viewing configuration. The level of sophistication of these images may vary from simple wire-frame representations, where objects are depicted as a set of segment lines, with no data on surfaces and volumes, to photorealistic rendering, where illumination effects are computed using the physical laws of light propagation. All the different approaches are based on the metaphor of a virtual camera positioned in 3D space and looking at the scene. Hence, independently from the rendering algorithm used, producing an image of the scene always requires the resolution of the following problems: 1. Modeling geometric relationships among scene objects, and in particular efficiently representing the situation in 3D space of objects and virtual cameras; 2. Culling and clipping, i.e. efficiently determining which objects are visible from the virtual camera; 3. Projecting visible objects on the film plane of the virtual camera in order to render them. This chapter provides an introduction to the field by presenting the standard approaches for solving the aforementioned problems.

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