Dr. Gunther Schrack
Professor Emeritus of Computer Engineering
Faculty Member, Institute for Computing, Information and Cognitive Systems
B.A.Sc., UBC (1958); M.A Sc., UBC (1960); Ph.D., ETH (1968). Visiting
Research Scientist, German National Research Laboratory for Informatics,
(1989/90).
Computer graphics, solid modelling; algorithms for quadtree and octree
modelling and display; spatial orders; spatial knowledge representation
and reasoning.
Research Interests
(1) Quadtrees and octrees are specialized data structures which are used for
the internal representation of pictures and solid objects, respectively.
Problems of interest are the efficient construction of quadtrees and octrees
from frame buffers, CAT scan slices, parametric generation, and by other
techniques. Efficient encoding and decoding algorithms as well as an arithmetic
which supports geometric transformations and other relevant manipulations were
recently developed.
(2) Spatial orders are mathematical transformations which map a
multi-dimensional discrete space onto the set of natural numbers. Due to their
general nature, a wide range of applications is known in many fields in the
applied sciences. Of particular research interest are problems such as those
listed for quadtrees and octrees above (which are spatial orders).
(3) In spatial knowledge representation and reasoning it is attempted to
extract implicit information contained in a graphical data base. Typical
research problems are, for example, searching for a specific object and
finding spatial relationships between objects.
Selected Publications
- X. Liu and G. Schrack,
``A new ordering strategy applied to spatial data processing'',
International Journal of Geographical Information Science,
12 (1: 1998), 3-22.
- X. Liu and G. Schrack,
``An algorithm for encoding and decoding the 3-D Hilbert order'',
IEEE Trans. Image Process., 6 (9: September 1997), 1333-1337.
- H.W. Cheung and G. Schrack,
``Progressive image transmission by linear quadtree coding and wavelet
transformation'',
Proc. IEEE Digital Signal Processing '97, July 1997,
Santorini, Greece.
- X. Liu and G. Schrack,
``Encoding and decoding the Hilbert order,'' Software--Practice
and Experience, 26 (12: December 1996), 1335-1346.
- L. Wilke and G. Schrack, ``Improved mirroring and rotation functions
for linear quadtree leaves,'' Image and Vision Computing, 13 (6:
August 1995), 491-495.
- U. Ast and G. Schrack, ``Translation of isothetic rectangles
in a linear quadtree domain,'' Proc. of 1995 IEEE Workshop on Nonlinear
Signal and Image Processing, June 1995, Neos Marmaras, Greece, 158-161.
- G. Schrack and X. Liu, ``The spatial U-order and some of its
mathematical characteristics,'' Proc. IEEE Pacific Rim Conf. on
Commun., Comput., and Signal Processing, May 1995, Victoria, B.C., 416-419.
- L. Stocco and G. Schrack, ``Integer dilation and contraction
for quadtrees and octrees,'' Proc. IEEE Pacific Rim Conf. on Commun.,
Comput., and Signal Processing, May 1995, Victoria, B.C., 426-428.
- L. Wilke and G. Schrack, ``Filling boundaries by insertion and
traversal in a linear quadtree domain,'' Proc. IEEE Pacific Rim
Conf. on Commun., Comput., and Signal Processing, May 1995, Victoria, B.C.
399-402.
- G. Schrack and I. Gargantini, ``Mirroring and rotating images in linear
quadtree form with few machine instructions,'' Image and Vision Computing,
11 (2: March 1993), 112-118.
- G. Schrack, ``Finding neighbors of equal size in linear quadtrees and
octrees in constant time,'' Computer Vision, Graphics, and Image Processing:
Image Understanding, 55 (3: May 1992), 221-230.
Copyright © 1997, Gunther F. Schrack. All rights reserved.
This page last updated: October 19, 2004.
This page maintained by
Dr. G.F. Schrack