Crowd simulation has been used in the entertainment industry to create populated environments that seem more realistic than isolated scenes, specially in urban areas. Video games are no exception, but the simulation of large crowds is often restrained by the remaining compute time available in CPUs, which is often used for most part of the game loop. This paper presents a parallel technique, using consumer grade graphics hardware, for proximity queries that is suitable for real-time crowd simulations. We use a truncated Voronoi diagram and a sampling technique, using ray marching, to find agents' neighbors in an environment texture. The experimental results suggest that our technique has significantly better performance than similar methods and can achieve simulations with thousands of agents in interactive frame rate.

Large-scale crowd simulation and visualization is crucial for the next generation of interactive virtual environments. Current authoring techniques produce good results but are laborious, and demand valuable graphics memory and computational resources beyond the reach of consumer-level hardware. In this paper, we propose a technique for generating animatable characters for crowds that reduces memory requirements. The first step consists in reducing, segmenting and labeling a data set of virtual characters into simpler body parts; labeling information is then manually generated and used to correctly match different body parts in order to generate new characters. The second step comprises a method to embed the rig and skinning information into the texture space shared among the new characters. Additional methods using color, skin features, pattern, fat, wrinkle and textile fold maps are used to add more variety. Animation sequences are stored in auxiliary textures. These can be transferred between different characters, as well as versions of the same characters with different level of detail; such animations can be modified, and otherwise reused, increasing variety yet reducing memory requirements. We will demonstrate that our technique has four advantages: first, memory requirements are reduced by 91% when compared to traditional libraries; second, it can also generate previously nonexistent characters from the original data set; third, embedding the rig and skinning into texture space allows painless animation transfer between different characters and fourth, between different levels of detail of the same characters.

Bicycles today are interfaces between civility and nature, between poetics and technological evolution. Jeffrey Shaw's classical piece The Legible City (1989) involves a stationary bicycle in the context of visual poetry, 3D texts, and geometries of uninhabited cities. The Legible City is an interface to virtual worlds. Text-shaped cities are projected and explored by visitors in a journey of reading. Twenty-two years after Shaw's work, one can use a stationary bicycle to travel through richer worlds, which are narrative applications of geography updated periodically such as Google Earth. In this sense students of Animation and Digital Art program at Tecnológico de Monterrey in Toluca, Mexico, developed four process art applications, using and adapting physical interfaces and videogame motion capture devices as their own take on Shaw's work.

Populated virtual environments need to be simulated with as much variety as possible. By identifying the most salient parts of the scene and characters, available resources can be concentrated where they are needed most. In this paper, we investigate which body parts of virtual characters are most looked at in scenes containing duplicate characters or clones . Using an eye-tracking device, we recorded fixations on body parts while participants were asked to indicate whether clones were present or not. We found that the head and upper torso attract the majority of first fixations in a scene and are attended to most. This is true regardless of the orientation, presence or absence of motion, sex, age, size, and clothing style of the character. We developed a selective variation method to exploit this knowledge and perceptually validated our method. We found that selective colour variation is as effective at generating the illusion of variety as full colour variation. We then evaluated the effectiveness of four variation methods that varied only salient parts of the characters. We found that head accessories, top texture and face texture variation are all equally effective at creating variety, whereas facial geometry alterations are less so. Performance implications and guidelines are presented.

Many efforts to improve interaction in virtual and augmented reality applications do so by including tactile elements to create a link between virtual objects and actions. It is also important to add collaboration, expanding single user interaction to networked user to user interaction. In this paper, we describe a networked virtual card game for multiple users based on a collaborative virtual environment. This game is a networked augmented reality game that uses an inexpensive tangible card flipping device allowing the system to be used in homes, museums, schools. The game is easy to set up and capable of hosting several remote users in a distributed system. We constructed two card flipping devices so we can show complete experimental results with two computers and their corresponding hardware interfaces

Imagination and creativity have always marked the path in the world of aesthetics; artists, designers and other creative individuals have found in the realm of computers a new canvas where illusions can come true, where new worlds can be designed and explored and where imagination can supersede or control the rules of physics. In this regard, one can speak of cyberart: it is a very expansive concept that includes the creation of interactive worlds. These worlds, by definition, need a way for users to become part of the art piece by modifying it trough time. Interactive techniques commonly used when developing human computer interfaces (HCI) for traditional virtual reality applications are not always suited for art applications. This is so because each art installation is unique and reflects the artist's point of view. This paper describes a particular interactive art piece, "Fluids" and how we solved the particular interface issues involved. We also discuss the process we followed for developing interaction hardware that must meet the requirements of this medium.

This work presents an integral system capable of generating animations with realistic dynamics, including the individualized nuances, of three-dimensional (3-D) human faces driven by speech acoustics. The system is capable of capturing short phenomena in the orofacial dynamics of a given speaker by tracking the 3-D location of various MPEG-4 facial points through stereovision. A perceptual transformation of the speech spectral envelope and prosodic cues are combined into an acoustic feature vector to predict 3-D orofacial dynamics by means of a nearest-neighbor algorithm. The Karhunen-Loe/spl acute/ve transformation is used to identify the principal components of orofacial motion, decoupling perceptually natural components from experimental noise. We also present a highly optimized MPEG-4 compliant player capable of generating audio-synchronized animations at 60 frames/s. The player is based on a pseudo-muscle model augmented with a nonpenetrable ellipsoidal structure to approximate the skull and the jaw. This structure adds a sense of volume that provides more realistic dynamics than existing simplified pseudo-muscle-based approaches, yet it is simple enough to work at the desired frame rate. Experimental results on an audiovisual database of compact TIMIT sentences are presented to illustrate the performance of the complete system.

Adding hair to virtual humans has focused on three important aspects: hair modeling, hair animation and hair rendering. We present an easy-to-use tool for hairstyling, modeling and animation of hair in real time. For modeling we use a paint-based interface to specify geometrical and styling characteristics of hair while for animation we use a simplified physical based approximation.

To improve the interaction of people with virtually generated environments we need first to break the barriers that prevent the user from getting an experience as close to reality as possible. The main problem is to give the user the sensation that his/her presence affects the virtual world and then to let the user perceive that the actions he/she takes on the real world can change the virtual one in a smooth natural way in order to achieve virtual biofeedback. Interacting with virtual nature can transport us out from reality. We developed an interactive application with two interfaces on which the user can pretend to be the wind and interact with a virtual pond. Our application makes the user believe and feel that he/she is modifying a 3D virtual pond by the interaction with a small water receptacle in the real world using innovative wave-sensing device. The user, by speaking to a microphone, can also interact with a virtual tree by making it move according to his/her wishes. The physics for the tree are calculated to present the user's action as a wind force making this an entertaining experience.

This article reports results of a modeling system that is part of a larger project which seeks to achieve perceptually realistic animations of 3D models driven by speech. This system generates individualized animated 3D face models driven by "muscles" and compatible with MPEG-4. Our main contribution is in the use of an extensive facial database and statistical techniques to generate plausible facial models from limited data: from a single image using eigenface-like statistical recognition techniques, from descriptions (identikit) or randomly within the parameters of the population represented in the facial database. An interactive module and a muscle-based animation player are also part of the system.

de Me ´xico during September 18-22, 2000

Abstract This article extends our previously published technique that allows several layers of clothing to be placed and animated over an articulated character by using implicit ellipsoidal muscles to generate a scalar field and placing each layer of clothing on a separate isosurface, thereby avoiding the use of any collision detection calculations between the different layers. The method is first extended to a class of characters that include a surface skin generated by a commercial animation package. A second extension combines isosurface placement with physically based methods. These extensions afford increased realism while retaining the performance obtained by using isosurfaces. Copyright © 2001 John Wiley & Sons, Ltd.

Presents a new way to model clothing worn by articulated implicit characters. A scalar field is produced using ellipsoids as primitives. Isosurfaces are then used to place garments in one or more layers. As each implicit surface is independent, collision detection is not needed. The cloth is a polygonal mesh whose vertices are in turn moved towards their destination isosurface using the gradient of the scalar field. In order to maintain the cloth's shape and size, a net of simple springs is used. We improve the appearance by adding noise to simulate wrinkles and light wind.