Computer Graphics and Geometric Modeling Seminar

Graphics and Geometric Modeling Seminar

• Meeting Time: Monday from 4pm to 5pm
• Place: 149 ASTeCC

This seminar is a weekly meeting of the Computer Science Department. Each meeting discusses a topic related to Computer Graphics (CG), Computer Aided Geometric Design (CAGD), or other related areas. The meeting is open to anyone interested in these areas.

Tentative Schedule of Speakers

• Sept 17, 1998
  
  Beyond the Desktop Metaphor: Toward More Effective Display, Interaction, and Telecollaboration in the Office of the Future via a Multitude of Sensors and Displays
  
  Dr. Henry Fuchs (Special Guest)
  
  Abstract:
  We are engaged in a long-term project to improve personal productivity for computer-related activities and tele-collaboration in an office environment of the future. We believe personal computer-related activities will be enhanced by capability to project imagery on any surface in the office, that together with precise head and eye-tracking, will enable head-tracked stereo imagery to be added to the user's views of his/her office environment --- creating a 3D immersive generalization of the now-ubiquitous 2D desktop metaphor as the principal human-computer interface. We plan to realize this kind of system by mounting many video projectors and video cameras around the room, especially around the ceiling. The projectors may provide the only source of light in the room and will allow detailed imagery to be projected (almost) everywhere in the office. In order to generate the appropriate imagery, however, a detailed 3D map of the changing office environment needs to be acquired. This will be acquired by measuring, with synchronized cameras and projectors, the precise 3D location(s) of the surface(s) light up by each pixel of each projector. Local collaboration will be enhanced by tracking each of several individuals in the office and generating (by time-division multiplexing or by other means), a stereo image pair appropriate for each individual. Objects under design, may be displayed, for each individual, from his/her own perspective and to his/her own specificiations of interest. TELE-collaboration activities, we believe will be enhanced by having such an enhanced office environment for each of the small group of distant collaborators, and displaying for each participant, in addition to the shared objects under discussion, some combination of the remote scenes that include the changing 3D images of each of the participants and 3D imges of physical objects of joint interest. To realize many of these capabilities, each user may need to wear polazired eyeglasses to perceive proper stereo imagery. Although initial results are encouraging, numerous difficult probleems remain -- how, for example, can imagery be projected onto a dark-colored surface in the room. The cost of such systems, with many projectors and cameras, image generators and image acquisition devices, may initially be prohibitively expensive, but is expected to decrease as the cost of such off-the-shelf equipment naturally decreases with increased market size. The positive psychological effects of working and interacting in such an immersive environment within a "standard" office will be so compelling, we believe, that users will not readily wish to return to working within the constrains of a 21" monitor. Much of this work is being carried out as part of a collaboration among the five sites of the NSF Science and Technology Center in Computer Graphics and Scientific Visualization (Brown, Caltech, Cornell, UNC, and Utah) and is also being carried on in collaboration with the GRASP Lab at University of Pennsylvania, and is part of the National Teleimmersion Initiative.
  
  
• Sept 21, 28, 1998
  
  Non-Uniform Recursive Subdivision Surfaces(Siggraph'98, pp.387-394)
  Dr. Cai-Ming Zhang
  
  Abstract:
  Doo-Sabin and Catmull-Clark subdivision surface are based on the notion of repeated knot insertion of uniform tensor product B-spline surfaces. This paper develops rules for non-uniform Doo-Sabn and Catmull-Clark surfaces that generalize non-uniform tensor product B-spline surfaces to arbitrary topologies. This added flexibility allows, among other things, the natural introduction of features such that cusps, creases, and darts, while elsewhere maintaining the same order of continuity as their uniform counterparts.
  
  
• Oct 5, 1998
  
  Java 3D
  Zheng Zhang
  
  Abstract:
  THE Java 3D API is an application programming interface used for writing three-dimensional graphics applications and applets. It gives developers high-level constructs for creating and manipulating 3D geometry and for constructing the structures used in rendering that geometry. Application developers can describe very large virtual worlds using these constructs, which provide Java 3D with enough information to render these worlds efficiently.
  
  
• Oct 12, 1998
  
  Subdivision Surfaces in Character Animation (Siggraph'98, pp.85-94)
  Dr. Fuhua(Frank) Cheng
  
  Abstract:
  The creation of believable and endearing characters in computer graphics presents a number of challengers, inclusing the modeling, animation and rendering of complex shapes such as heads, hands, and clothing. Traditionally, these shapes have been modeled with NURBS surfaces despite the severe topological restrictions that NURBS impose. In order to move beyond these restrictions, subdivision surfaces have been introduced recently into the production environment at Pixar. Subdivision surfaces are not new, but their use in high-end CG production has been limited.
  A series of developments that were required in order for subdivison surfaces to meet the demands of high-end production are described. First, a practical technique for constructing provably smooth variable-radius fillets and blends are devised. Second, methods for using subdivison surfaces in clothing simulation including a new algorithm for efficient collision detection are developed. Third, a method for constructing smooth scalar fields on subdivision surfaces is developed. This method enables the use of a wider class of programmable shaders. These developments, which were used extensively at Pixar's recently completed short film "Geri's game", have become a highly valued feature of Pixar's production envoronment.
• Oct 28, 1998
  
  A Distributed 3D Graphics Library (Siggraph'98, pp.361-370)
  Zheng Zhang
  
  Abstract:
  Repo-3D is a general-purpose, object-oriented library for developing distributed, intereactive 3D graphics applications across a range of heterogeneous workstations. Repo-3D is designated to make it easy for programmers to rapidly build prototypes using a familiar multi-purpose remote and replicated objects, presenting the illusion of a single distributed shared memory. Graphical objects are diretly distributed, circumventing the duplicate database problem and allowing programmers to focus on the application details.