133 results for Klette, Reinhard, Report

Height data from gradient fields
Klette, Reinhard; Schluns, Karsten (199608)
Report
The University of Auckland LibraryThe paper starts with a review of integration techniques for calculating height maps from dense gradient fields. There exist a few proposals of local integration methods (Coleman/Jain 1982, Healey/Jain 1984, Wu/Li 1988, Rodehorst 1993), and two proposals for global optimization (Horn/Brooks 1986 and Frankot/ Chellappa 1988). Several experimental evaluations of such integration techniques are discussed in this paper. The examined algorithms received high markings on curved objects but low markings on polyhedral shapes. Locally adaptive approaches are suggested to cope with complex shapes in general.
View record details 
Evaluation of Algorithms for Linear Shape from Shading
Kozera, Ryszard; Klette, Reinhard (1997)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). We analyse different sequential algorithms for the recovery of object shape from a single shading pattern generated under the assumption of a linear reflectance map. The algorithms are based on the finite difference approximation of the derivatives. They operate on a rectangular discrete image (or part of it) and use the height of the soughtafter surface along a curve in the image (image boundary) as initial data. The evaluation of different numerical schemes is achieved by comparing stability, convergence, and domains of influence of each scheme in question. The relative difficulty of handling a linear case indicates that the case of nonlinear reflectance maps is far from being trivial.
View record details 
Euclidean Shortest Paths in Simple Polygons
Li, Fajie; Klette, Reinhard (2007)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). Let p and q be two points in a simple polygon P. This chapter provides two rubberband algorithms for computing a shortest path between p and q that is contained in P. The two algorithms are based on previously known results on triangular or trapezoidal decompositions of simple polygons, and have either kappa(epsilon) times O(n) or kappa(epsilon) times O(n log n) time complexity, where kappa(epsilon) = (L0  L)/epsilon, for the true length L of the shortest path and length L0 of a used initial polygonal path. Rubberband algorithms follow a straightforward design strategy, and the proposed algorithms ar easy to implement (after having the decompositions at hand).
View record details 
Touring Polygons, Parts Cutting, and qRectangles
Li, Fajie; Klette, Reinhard (2007)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). Given a sequence of k simple polygons in a plane, a start point p, and a target point q. We approximately compute a shortest path that starts at p, then visits each of the polygons in the specified order, and finally ends at q. So far no solution was known if the polygons are pairwise disjoint and nonconvex. By applying a rubberband algorithm, we give an approximative algorithm with time complexity in kappa(epsilon) times O(n), where n is the total number of vertices of the given polygons, and function kappa(epsilon) is as follows: kappa(epsilon) = (L_0  L)/epsilon, where L_0 is the length of the initial path, and L is the true (i.e., optimum) path length. The given rubberband algorithm can also be applied to solve approximately three NPcomplete or NPhard 3D Euclidean shortest path (ESP) problems in time kappa(epsilon) times O(k), where k is the number of layers in a stack which contains the defined obstacles.
View record details 
Decomposing a Simple Polygon into Trapezoids
Li, Fajie; Klette, Reinhard (2007)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). Chazelle's triangulation \cite{BC1991} forms today the common basis for lineartime Euclidean shortest path (ESP) calculations (where start and end point are given within a simple polygon). This paper provides an alternative method for subdividing a simple polygon into ``basic shapes'', using trapezoids instead of triangles. The authors consider the presented method as being substantially simpler than the lineartime triangulation method. However, it requires a sorting step (of a subset of vertices of the given simple polygon); all the other subprocesses are linear time.
View record details 
Analysis of the Rubberband Algorithm
Li, Fajie; Klette, Reinhard (2006)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). We consider simple cubecurves in the orthogonal 3D grid of cells. The union of all cells contained in such a curve (also called the tube of this curve) is a polyhedrally bounded set. The curve's length is defined to be that of the minimumlength polygonal curve (MLP) contained and complete in the tube of the curve. Only one general algorithm, called rubberband algorithm, was known for the approximative calculation of such an MLP so far. An open problem in KLE_ROS_2004 is related to the design of algorithms for the calculation of the MLP of a simple cubecurve: Is there a simple cubecurve such that none of the nodes of its MLP is a grid vertex? This paper constructs an example of such a simple cubecurve, and we also characterize the class of all of such cubecurves. This study leads to a correction in Option 3 of the rubberband algorithm (by adding one missing test). We also prove that the rubberband algorithm has linear time complexity ${\cal O}(m)$ where $m$ is the number of critical edges of a given simple cube curve, which solves another open problem in the context of this algorithm.
View record details 
MinimumLength Polygons of FirstClass Simple CubeCurves
Li, Fajie; Klette, Reinhard (2005)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). We consider simple cubecurves in the orthogonal 3D grid. The union of all cells contained in such a curve (also called the tube of this curve) is a polyhedrally bounded set. The curve's length is defined to be that of the minimumlength polygonal curve (MLP) fully contained and complete in the tube of the curve. So far only one general algorithm called rubberband algorithm was known for the approximative calculation of such an MLP. A proof that this algorithm always converges to the correct curve, is still an open problem. This paper proves that the rubberband algorithm is correct for the family of firstclass simple cubecurves.
View record details 
Understanding Human Motion: A Historic Review
Klette, Reinhard; Tee, Garry (2007)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). Understanding human motion is based on analyzing global motion patterns, rather than on studying local patterns such as hand gestures or facial expressions. This report reviews briefly (by selection, not by attempting to cover developments, and with a focus on Western History) people and contributions in science, art, and technology which contributed to the field of human motion understanding. This review basically stops at the time when advanced computing technology became available for performing motion studies based on recorded image data or extensive (modelbased) calculations or simulations.
View record details 
A Comparison of Property Estimators in Stereology and Digital Geometry
Huang, Yuman; Klette, Reinhard (2004)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). We consider selected geometric properties of 2D or 3D sets, given in form of binary digital pictures, and discuss their estimation. The properties examined are perimeter and area in 2D, and surface area and volume in 3D. We evaluate common estimators in stereology and digital geometry according to their multiprobe or multigrid convergence properties, and precision and efficiency of estimations.
View record details 
A New Algorithm for Gradient Field Integration
Wei, Tiangong; Klette, Reinhard (2001)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). This paper proposes two improvements for reflectance based shape recovery. First, it is shown that albedoindependent photometric stereo allows albedo computation. This computation is based on photometric equations that relate surface normals to triplets of the image irradiances. Second, the paper also presents as the main result a new algorithm for depth recovery from surface normals. In order to improve the accuracy and robustness and to strengthen the relation between the depth map and surface normals, two new constraints are added into the associated cost function. They constrain the behavior of highorder change rate between the variables. Therefore, the changes of depth maps will be more regular. The FrankotChellappaalgorithm is a special case of our algorithm in the sense that it uses a subset of constraints only.
View record details 
Interactions between Number Theory and Image
Klette, Reinhard; Zunic, Jovisa (2000)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). The conceptual design of many procedures used in image analysis starts with models which assume as an input sets in Euclidean space which we regard as real objects. However, the application finally requires that the Euclidean (real) objects have to be modelled by digital sets, i.e. they are approximated by their corresponding digitizations. Also "continuous" operations (for example integrations or differentiations) are replaced by "discrete" counterparts (for example summations or differences) by assuming that such an replacement has only a minor impact on the accuracy or efficiency of the implemented procedure. This paper discusses applications of results in number theory with respect to error estimations, accuracy evalua tions, correctness proofs etc. for image analysis procedures. Knowledge about digitization errors or approximation errors may help to suggest ways how they can be kept under required limits. Until now have been only minor impacts of image analysis on developments in number theory, by defining new problems, or by specifying ways how existing results may be discussed in the context of image analysis. There might be a more fruitful exchange between both disciplines in the future.
View record details 
Approximate ESPs on Surfaces of Polytopes Using a Rubberband Algorithm
Li, Fajie; Klette, Reinhard (2007)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). Let p and q be two points on the surface of a polytope P . This report provides a rubberband algorithm for computing a Euclidean shortest path between p and q (surface ESP) that is contained on the surface of P . The algorithm has k1(e) · k2(e) · O(n^2) time complexity, where n is the number of vertices of P , ki(e) = (L0i  Li )/e, for the true length Li of some shortest path with initial (polygonal path) length L0i (used when approximating this shortest path), for i = 1, 2. Rubberband algorithms follow a straightforward design strategy, and the proposed algorithm is easy to implement and thus of importance for applications, e.g. when analyzing 3D ob jects in 3D image analysis (such as in biomedical or industrial image analysis, using 3D image scanners).
View record details 
Digital Visibility and Visualisation of Magnetic Resonance Imaging Series
Yip, Ben; Klette, Reinhard (1997)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). This paper reports about two new approaches to visualise the threedimensional object that is depicted by a MR (Magnetic Resonance) imaging series. The exterior of the object is visualised with a surface rotation approach, which is based on the concept of digital visibility. The interior of the object is visualised with a cut and view approach, which is based on a special solution for resampling. After image data preprocessing, the surface rotation approach allows the user to rotate and visualise the object in any angle of view; while the cut and view approach let the user see the interior of the object by creating a planar cut onto the three dimensional object and then visualise the crosssection. These two approaches complement each other. Together, they provide a simple, fast processing method for the medical experts to visualise the MR imaging series. The time complexity and the quality of the outcome are satisfactory even it is processed with Intel 486 processor.
View record details 
Multiresolution Surface Reconstruction: Edge Collapsing + Simplification Envelopes
Zhou, Shaozheng; Klette, Reinhard (1997)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). Multiresolution surfaces are especially useful for fast rendering, realtime display, and progressive transmission. This paper reviews major surface simplification techniques and multiresolution surface reconstruction approaches. Based on comparison among various approximation algorithms we propose an appropriate measure for surface approximation accuracy and essential concepts for multiresolution surface reconstruction. Having analyzed the surface simplification process, we propose our solution for multiresolution surface reconstruction  combination of the edge collapsing operation and simplification envelopes, which can generate continuous multiresolution surfaces with globallyguaranteed approximation errors.
View record details 
The Class of Simple CubeCurves Whose MLPs Cannot Have Vertices at Grid Points
Li, Fajie; Klette, Reinhard (2004)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). We consider simple cubecurves in the orthogonal 3D grid of cells. The union of all cells contained in such a curve (also called the tube of this curve) is a polyhedrally bounded set. The curve's length is defined to be that of the minimumlength polygonal curve (MLP) fully contained and complete in the tube of the curve. So far only one general algorithm called rubberband algorithm was known for the approximative calculation of such a MLP. There is an open problem which is related to the design of algorithms for calculation a 3D MLP of a cubecurve: Is there a simple cubecurve such that none of the vertices of its 3D MLP is a grid vertex? This paper constructs an example of such a simple cubecurve. We also characterize this class of cubecurves.
View record details 
Curves, Hypersurfaces, and Good Pairs of Adjacency Relations
Brimkov, Valentin; Klette, Reinhard (2004)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). In this report we propose several equivalent definitions of digital curves and hypersurfaces in arbitrary dimension. The definitions involve properties such as onedimensionality of curves and (n ? 1)dimensionality of hypersurfaces that make them discrete analogs of corresponding notions in topology. Thus this work appears to be the first one on digital manifolds where the definitions involve the notion of dimension. In particular, a digital hypersurface in nD is an (n?1)dimensional object, as it is in the case of continuous hypersurfaces. Relying on the obtained properties of digital hypersurfaces, we propose a uniform approach for studying good pairs defined by separations and obtain a classification of good pairs in arbitrary dimension.
View record details 
Combinatorics on Incidence Pseudographs
Klette, Reinhard (2003)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). Incidence pseudographs (or the dual model of complexes based on a boundedby relation) are popular models for pixels or voxels and relations between these. They allow a definition of a topological space, and combinatorial formulas characterize open and closed sets in this topology. K. Voss characterized in 1993 open regions in incidence pseudographs. This article reviews these results and provides also combinatorial formulas for closed regions.
View record details 
Recovery of Coloured Surface Reflectances Using the Photometric Stereo Method
Chen, ChiaYen; Klette, Reinhard; Chen, ChiFa (2002)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). We discuss a fast and efficient method to estimate the surface reflectance values with respect to different wavelength of light. Qualitative and quantitative evaluations show that surfaces rendered using surface reflectances obtained by the proposed method are more realistic when compared with conventional rendering methods.
View record details 
Analysis of Finite Difference Algorithms for Linear Shape from Shading
Wei, Tiangong; Klette, Reinhard (2000)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). This paper presents and analyzes four explicit, two implicit and four semiimplicit finite difference algorithms for the linear shape from shading problem. Comparisons of accuracy, solvability, stability and convergence of these schemes indicate that the weighted semiimplicit scheme and the box scheme are better than the other ones because they can be calculated more easily, they are more accurate, faster in convergence and unconditionally stable.
View record details 
Towards Experimental Studies of Digital Moment Convergence
Klette, Reinhard; Zunic, Jovisa (2000)
Report
The University of Auckland LibraryYou are granted permission for the noncommercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (fortyfive) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s). Digital moments approximate real moments where the accuracy depends upon grid resolution. There are theoretical results about the speed of convergence. However, there is a lack of more detailed studies with respect to selected shapes of regions, or with respect to experimental data about convergence. This paper discusses moments for specific shapes of regions, and provides some initial experimental data about measured convergence of digital moments.
View record details