3D graphics eBook - Course Materials Repository

Irregular Z-buffer 66
Applications
The irregular Z-buffer can be used for any application which requires visibility calculations at arbitrary locations in
the image plane. It has been shown to be particularly adept at shadow mapping, an image space algorithm for
rendering hard shadows. In addition to shadow rendering, potential applications include adaptive anti-aliasing,
jittered sampling, and environment mapping.
External links
• The Irregular Z-Buffer: Hardware Acceleration for Irregular Data Structures [1]
• The Irregular Z-Buffer And Its Application to Shadow Mapping [2]
• Alias-Free Shadow Maps [3]
• Fast Triangle Rasterization using irregular Z-buffer on CUDA [4]
References
[1] http:/ / www. tacc. utexas. edu/ ~cburns/ papers/ izb-tog. pdf
[2] http:/ / www. cs. utexas. edu/ ftp/ pub/ techreports/ tr04-09. pdf
[3] http:/ / www. tml. hut. fi/ ~timo/ publications/ aila2004egsr_paper. pdf
[4] http:/ / publications. lib. chalmers. se/ records/ fulltext/ 123790. pdf
Isosurface
An isosurface is a three-dimensional analog of an isoline. It is a
surface that represents points of a constant value (e.g. pressure,
temperature, velocity, density) within a volume of space; in other
words, it is a level set of a continuous function whose domain is
3D-space.
Isosurfaces are normally displayed using computer graphics, and are
used as data visualization methods in computational fluid dynamics
(CFD), allowing engineers to study features of a fluid flow (gas or
liquid) around objects, such as aircraft wings. An isosurface may
represent an individual shock wave in supersonic flight, or several
isosurfaces may be generated showing a sequence of pressure values in
the air flowing around a wing. Isosurfaces tend to be a popular form of
visualization for volume datasets since they can be rendered by a
simple polygonal model, which can be drawn on the screen very
quickly.
Zirconocene with an isosurface showing areas of
the molecule susceptible to electrophilic attack.
Image courtesy of Accelrys (http:/ / www.
accelrys. com)
In medical imaging, isosurfaces may be used to represent regions of a particular density in a three-dimensional CT
scan, allowing the visualization of internal organs, bones, or other structures.
Numerous other disciplines that are interested in three-dimensional data often use isosurfaces to obtain information
about pharmacology, chemistry, geophysics and meteorology.
A popular method of constructing an isosurface from a data volume is the marching cubes algorithm, and another,
very similar method is the marching tetrahedrons algorithm.