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MPI-INF D4 Publications :: Thesis :: Ghali, Sherif

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Thesis - Doctoral dissertation | @PhdThesis | Doktorarbeit

Author(s)*:Ghali, Sherif
BibTeX citekey*:Ghali1999

Title, School
Title*:A Geometric Framework for Computer Graphics Addressing Modeling, Visibility, and Shadows
School:University of Toronto
Type of Thesis*:Doctoral dissertation

Note, Abstract, Copyright
LaTeX Abstract:The main question this dissertation addresses is the following: Is it

possible to design a computer graphics API such that
modeling primitives, computing visibility, and generating shadows from
point, linear, and area light sources can be conveniently and
concisely expressed?

The thesis answers this question in the affirmative by describing a
framework for geometric computing in computer graphics. The classes in
the layered system constituting the framework are described using the
UML notation and each algorithm presented is encapsulated in a member
method of a class in the hierarchy.

We identify a number of abstractions for object--space graphics such
as transparent visibility and opaque visibility. These abstractions
are somewhat harder to implement than standard rasterized
abstractions as they rely on graphs and planar maps. Nevertheless,
these notions prove to be fundamental in this work on object--space
graphics and also appear to be fundamental for computer graphics in

We propose that clients of a graphics API such as the one presented
here should be relieved from the onus of computing shadows and we show
that the computation of shadows can be automated and encapsulated in
the framework. We address illumination under a point, a linear, and an
area light source in space. We also fully address modeling,
visibility, and shadow problems in the plane. Planar problems both give us
valuable intuition before tackling the problems in space and are useful
for graphical environments such as mazes.

The thesis also proposes ways for minimizing objects in a geometric
framework. We show that a variation on the winged--edge data structure
can be encapsulated to represent topology and describe how a
programming language supporting genericity allows us to instantiate
the topological classes and their iterators for use in modeling a
scene, in representing its view in object--space, and
in representing the scene when its topology is refined to include
shadow edges.

The computation is done entirely in object--space. Some of the
advantages of object--space computation are that the shadow edges are
determined symbolically, the time spent on shading is proportional to
the visible features of the scene, and the output is both concise and

Keywords:Modeling, Visibility, Shadows, Linear light source, Area light source, object-space computation, 2D/flatland and 3D graphics, UML - Unified Modeling Language, Class hierarchy
HyperLinks / References / URLs:

Referees, Status, Dates
Date Kolloquium:6 August 2020

MPG Unit:Max-Planck-Institut für Informatik
MPG Subunit:Computer Graphics Group
Audience:experts only
Appearance:MPII WWW Server, MPII FTP Server, university publications list, working group publication list, Fachbeirat

BibTeX Entry:
AUTHOR = {Ghali, Sherif},
TITLE = {A Geometric Framework for Computer Graphics Addressing Modeling, Visibility, and Shadows},
SCHOOL = {University of Toronto},
YEAR = {1999},
TYPE = {Doctoral dissertation}
MONTH = {June},

Entry last modified by Sherif Ghali, 03/12/2010
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Sherif Ghali
03/07/2000 04:31:56 PM

Sherif Ghali

Edit Date
07/03/2000 16:31:56