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|Title: ||Two novel spherical representations and their applications|
|Other Titles: ||Liang zhong xin ying de qiu mian biao da fang fa ji qi ying yong|
|Authors: ||Ho, Tze Yui ( 何子銳)|
|Department: ||Department of Electronic Engineering|
|Degree: ||Doctor of Philosophy|
|Issue Date: ||2010|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Computer graphics.|
Three-dimensional display systems.
|Notes: ||CityU Call Number: T385 .H6 2010|
xiv, 102 leaves : ill. (some col.) 30 cm.
Thesis (Ph.D.)--City University of Hong Kong, 2010.
Includes bibliographical references (leaves 97-102)
|Abstract: ||In this thesis, two novel spherical representations are introduced for two different
applications in computer graphics, one for environment mapping and the other for
pre-computed radiance transfer approaches. The first novel representation is unicube
mapping, and the second one is vectorized visibility.
Unicube mapping Cube mapping is widely used in many graphics applications
due to the availability of hardware support. However, it does not sample the spherical
surface evenly. A recent uniform spherical mapping, isocube mapping, samples the
spherical surface evenly and exploits the six-face structure. Unfortunately, some texels
in isocube mapping are not rectilinear in shape which can degrade the filtering quality.
This thesis proposes a novel spherical mapping, namely unicube mapping, that has
the advantages of cube mapping (exploitation of hardware and rectilinear structure)
and isocube mapping (uniform sampling). Unicube mapping uses a simple function to
modify the look-up vector before the conventional cube map look-up process. Hence,
unicube mapping fully exploits the cube map hardware for real-time filtering and
look-up. More importantly, its rectilinear partition structure allows a direct and realtime
acquisition of environment maps via perspectively projecting a 3D scene on the
faces of unicube map. This property facilitates dynamic environment mapping.
Vectorized visibility Most existing pre-computed radiance transfer approaches
for geometric relighting are vertex based. To preserve the fidelity of high frequency
effects, a 3D model must be highly tessellated, otherwise artifacts due to interpolation
will appear. This thesis presents a novel spherical representation for visibility representation,
namely vectorized visibility, along with its geometric relighting algorithm.
As vectorized visibility is also a form vector graphics, we can interpolate vectorized
visibilities to synthesize the vectorized visibility of an on-screen pixel for the lighting
evaluations, analogous to the morphing of vector graphics. Therefore, the artifacts
due to interpolation are eliminated while preserving the high frequency shadows, even
for the coarsely tessellated 3D models. In addition, our geometric relighting algorithm
allows rotating lighting environment, changing viewing, and adjusting the shininess
during rendering in an interactive manner. For isotropic reflection, the specular level
can be adjusted from blurry to mirror reflection. Our geometric relighting algorithm
can also be combined with some existing rendering algorithms to provide a better
realism, e.g. dynamic bump mapping and the doubly-projected SH approach.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b4086689|
|Appears in Collections:||EE - Doctor of Philosophy |
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