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.

This page maintained by Dr. G.F. Schrack