## Books and Course Notes

 Warping and Morphing of Graphical Objects Jonas Gomes, Bruno Costa da Silva, Lucia Darsa and Luiz Velho Morgan Kaufman Publishers, San Francisco, CA [Morgan Kaufman] [Amazon] [Barnes and Noble]
 Warping and Morphing of Graphical Objects Jonas Gomes, Bruno Costa da Silva, Lucia Darsa and Luiz Velho SIGGRAPH '97, Course Notes #34, ACM, Los Angeles, CA
 Warping and Morphing of Graphical Objects Jonas Gomes, Bruno Costa da Silva, Lucia Darsa and Luiz Velho SIGGRAPH '95, Course Notes #3, ACM, Los Angeles, CA
 Deformação e Metamorfose de Objetos Gráficos Jonas Gomes, Bruno Costa da Silva, Lucia Darsa and Luiz Velho 20th Brazilian Colloquium in Mathematics, July 1995, IMPA/CNPq, Rio de Janeiro, Brazil

## Conferences and Journals

 A System’s Architecture for Warping and Morphing of Graphical Objects Jonas Gomes, Lucia Darsa, Bruno Costa and Luiz Velho Proceedings of SIBGRAPI'98, SBC, Oct 1998 [sib98.pdf]

This paper describes a system architecture that enables the use of different techniques of warping and morphing applied to various classes of graphical objects (images, surfaces, plane curves, volumetric data, implicit surfaces etc.) Combinations of warping and morphing techniques can lead to more powerful and expressive results. The possibility of experimenting with alternative techniques for distinct classes of graphical objects creates a very flexible and robust warping and morphing system.

 Walkthroughs of Complex Environments using Image-based Simplification Lucia Darsa, Bruno Costa da Silva and Amitabh Varshney Computers and Graphics, Jan 98

We present an image-based technique to accelerate the navigation in complex static environments. We perform an image-space simplification of each sample of the scene taken at a particular viewpoint, and dynamically combine these simplified samples to produce images for arbitrary viewpoints. Since the scene is converted into a bounded complexity representation in the image space, with the base images rendered beforehand, the rendering speed is relatively insensitive to the complexity of the scene. The proposed method correctly simulates the kinetic depth effect (parallax), occlusion, and can resolve the missing visibility information. This paper describes a suitable representation for the samples, a specific technique for simplifying them, and different morphing methods for combining the sample information to reconstruct the scene. We use hardware texture mapping to implement the image-space warping and hardware affine transformations to compute the viewpoint-dependent warping function.

 Enabling Virtual Reality for Large Scale Mechanical CAD Datasets Amitabh Varshney, Jihad El-Sana, Francine Evans, Lucia Darsa, Bruno Costa da Silva and Steve Skiena Proceedings of DETC’97, ASME Design Engineering Technical Conference, Sep 1997 [asme97.pdf]

Reconciling scene realism with interactivity has emerged as one of the most important areas in making virtual reality feasible for large-scale mechanical CAD datasets consisting of several millions of primitives. This paper surveys our research and related work for achieving interactivity without sacrificing realismn in virtual reality walkthroughs and flythroughs of polygonal CAD datasets. We outline our recent work on efficient generation of triangle strips from polygonal models that takes advantage of compression of connectivity information. This results in substantial savings in rendering, transmission and storage. We outline our work on genus-reducing simpliciations as well as real-time view-dependent simplifications that allow on-the-fly selection amongst multiple levels of detail, based upon lighting and viewing parameters. Our method allows multiple lvels of detail to coexist on the same object at different regions and to merge seamlessly without any cracks or shading artifacts. We also present an overview of our work on hardware-assisted image-based rendering that allows interactive exploration of computer generated scenes.

 Navigating Static Environments Using Image-space Simplification and Morphing Lucia Darsa, Bruno Costa da Silva and Amitabh Varshney ACM/SIGGRAPH 97 Symposium on Interactive 3D Graphics, Providence, RI, Apr 1997 [symp3d97.pdf]

We present a $z$-buffered image-space-based rendering technique that allows navigation in complex static environments. The rendering speed is relatively insensitive to the complexity of the scene as the rendering is performed {\em a priori}, and the scene is converted into a bounded complexity representation in the image space. Real-time performance is attained by using hardware texture mapping to implement the image-space warping and hardware affine transformations to compute the viewpoint--dependent warping function. Our proposed method correctly simulates the kinetic depth effect (parallax), occlusion, and can resolve the missing visibility information by combining $z$-buffered environment maps from multiple viewpoints.

 Multiresolution Representation and Reconstruction of Adaptively Sampled Images L. Darsa, B. Costa. Proceedings of SIBGRAPI'96, SBC, pp. 321–328, Oct 1996 [sib96_ps.zip]

We present a method for sampling, structuring and reconstructing progressively refined images effectively. This has direct applications to progressive refinement of the result of slow renderers, such as ray tracers, and to the progressive transmission of images on slow media, as in world wide web browsers. Sampling images adaptively with respect to frequency at the back end provides a more compact representation. These samples are then structured at the front end using Voronoi or Delaunay tesselations, and reconstructed with $C^0$ continuity taking advantage of standard 3D acceleration hardware. The structuring scheme is extended to handle multiresolution images, with optional antialiasing, allowing the representation of an arbitrary level of detail without penalizing the reconstruction.

 Graphical Objects J. Gomes, B. Costa, L. Darsa, L. Velho The Visual Computer 12(6), Jun 1996 [viscomp96.pdf]

In this paper we introduce the concept of a graphical object, and the abstraction paradigms to study them, and apply them in computer graphics. Intuitively, a graphical object encompasses all of the entities that are manipulated in a graphics system. This concept makes it possible to unify similar research topics that have appeared in the literature in a rather separated way. As an application, we use the concept of graphical object to study the problem of object metamorphosis, which includes as a particular case the problem of image metamorphosis. Although we are not primarily concerned with implementation issues in this paper, the concepts we introduce can be exploited for systems design and development using object oriented programming.

 Image Deformation and Metamorphosis B. Costa, L. Darsa and J. Gomes SIBGRAPI '92, Aguas de Lindoia, Sao Paulo, Brazil, Nov 1992 [sib92.ps.Z]

Metamorphosis is simply a complete change of shape, structure or substance of one object into another (Webster, 1989). This kind of trnasformation is a very effective tool that has been widely used by the film and video industry. In this paper, we give a conceptual overview of the metamorphosis problem and define precisely the meaning of image metamorphosis (also called image morphing). We analyze existing morphing techniques under this conceptual framework, and propose a new technique that explores some advantages of different existing methods.

 Ray: Um ray tracer extensível e orientado a objetos B. Costa and L. Darsa Graduation Project, Department of Computer Science, PUC-Rio, Rio de Janeiro, Brazil, 1992 [ray91_ps.zip (portuguese, missing equations)]

## Master Thesis and Project

 Accelerated 3D Navigation using Environment Mapping and Real-time Morphing Lucia Darsa Advised by Amitabh Varshney Master's project, Department of Computer Science, SUNY at Stony Brook, Aug 1996. (available upon request)

The goal of this project is to allow real time navigation in complex static environments. The complexity of the scene will not affect substantially the speed of the interaction, as the rendering is performed a priori, and the scene is converted into a bounded complexity representation in eye space. The real time performance is attained by using hardware texture mapping to implement the warping, and hardware affine transformations to compute the viewpoint--dependent warping function. The proposed method is able to correctly handle the occlusions and the parallax effect, and can determine the visibility information for any arbitrary viewpoint and viewing directions. The a priori rendering of the scene can be done by any algorithm that is able to generate range information.

 Deformation and Metamorphosis of Graphical Objects Lucia Darsa Master’s Thesis, July 1994, Pontifical Catholic University of Rio de Janeiro, Brazil Advised by Jonas de Miranda Gomes and co-advised by Bruno Feijo [darsa94p_ps.zip (portuguese) ] [darsa94ppt.zip (presentation)] (english version available upon request)

Metamorphosis is defined as a complete change of shape, structure or substance of something. This common sense dictionary definition corresponds to the three main forms of information that must be represented in object models: geometry, topology and properties. This dissertation attempts to describe and analyze the metamorphosis problem in Rn, through the use of objects general enough to encompass, in essence, all classical forms of representation in R2 and R3. Existing techniques are analyzed as subcases of the generalization, integrating the treatment given to the previously dissociated 2D and 3D metamorphosis problems, and allowing the sharing of some of the techniques. A new approach for 3D metamorphosis, based on a 2D technique, and an implementation are described.

## Magazines

 All You Ever Wanted to Know About Morphing (but were afraid to ask...) Bruno Costa da Silva and Lucia Darsa AC's TECH for the Commodore Amiga, 3(3), 1993, PiM Publications, Fall River, MA

## Covers

 Sibgrapi'96 Proceedings Cover Lucia Darsa and Bruno Costa SIBGRAPI '96, Caxambu, Minas Gerais, Brazil, October 1996
 Sibgrapi'92 Proceedings Cover Bruno Costa, Lucia Darsa and Jonas Gomes SIBGRAPI '92, Aguas de Lindoia, Sao Paulo, Brazil, Nov 1992