## Information

- Publication Type: Technical Report
- Workgroup(s)/Project(s): not specified
- Date: January 1994
- Number: TR-186-2-94-10
- Keywords: visibility, scan-line algorithm, Constructive Solid Geometry (CSG), quadrics, coherence

## Abstract

Scan-line algorithms for visibility calculation
exploit various types of coherence properties.
Several scan-line algorithms for Constructive
Solid Geometry (CSG) are discussed. In one approach
CSG primitives are represented by polygonal
approximations. Another technique processes CSG
primitives as general quadric surfaces. We
investigate the handling of frequently occurring
quadric surfaces (cube, cone, sphere, cylinder)
as distinct cases. Thus the differing properties
of such objects can be used more efficiently than a
uniform approach would allow. A so called eBRep
(extended Boundary Representation) is defined for
the frequently occurring quadric surfaces. An eBRep
is an exact representation of a quadric object and
contains curved edges and faces. For each of the
above mentioned quadric surfaces a different, geometry
dependent eBRep is specified. A comparison between the
polygon-based scan-line algorithm for CSG and our
eBRep based approach is done. eBRep is a storage
efficient exact representation of quadric surfaces,
well suited for scan-line visibility determination.

## Additional Files and Images

## Weblinks

No further information available.

## BibTeX

@techreport{Groeller-1994-CSA,
title = "Coherence in scan-line algorithms for CSG",
author = "Meister Eduard Gr\"{o}ller and Peter Brunner",
year = "1994",
abstract = "Scan-line algorithms for visibility calculation exploit
various types of coherence properties. Several scan-line
algorithms for Constructive Solid Geometry (CSG) are
discussed. In one approach CSG primitives are represented by
polygonal approximations. Another technique processes CSG
primitives as general quadric surfaces. We investigate the
handling of frequently occurring quadric surfaces (cube,
cone, sphere, cylinder) as distinct cases. Thus the
differing properties of such objects can be used more
efficiently than a uniform approach would allow. A so called
eBRep (extended Boundary Representation) is defined for the
frequently occurring quadric surfaces. An eBRep is an exact
representation of a quadric object and contains curved edges
and faces. For each of the above mentioned quadric surfaces
a different, geometry dependent eBRep is specified. A
comparison between the polygon-based scan-line algorithm for
CSG and our eBRep based approach is done. eBRep is a storage
efficient exact representation of quadric surfaces,
well suited for scan-line visibility determination.",
month = jan,
number = "TR-186-2-94-10",
address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria",
institution = "Institute of Computer Graphics and Algorithms, Vienna
University of Technology ",
note = "human contact: technical-report@cg.tuwien.ac.at",
keywords = "visibility, scan-line algorithm, Constructive Solid Geometry
(CSG), quadrics, coherence",
URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Groeller-1994-CSA/",
}