scholarly journals Reassembling 3D Thin Fragments of Unknown Geometry in Cultural Heritage

2014 ◽  
Vol II-5 ◽  
pp. 393-399 ◽  
Author(s):  
S. Y. Zheng ◽  
R. Y. Huang ◽  
J. Li ◽  
Z. Wang
Keyword(s):  
Maximum Likelihood ◽  
3D Model ◽  
Numerical Instabilities ◽  
Error Accumulation ◽  
Geometric Assumption ◽  
Rigid Transformations ◽  
Cartesian Coordinate ◽  
Curvature And Torsion ◽  
Alignment Errors ◽  
Structure Light

Many fragile antiques had already been broken upon being discovered at archaeology sites. The fragments of these objects cannot be effectively interpreted and studied unless they are successfully reassembled. However, there still exists many problems in the reassembly procedure in existing methods, such as the numerical instabilities of curvature and torsion based methods, the limitation of geometric assumption, and the error accumulation of the pairwise matching approach, etc. Regarding these problems, this paper proposed an approach to match the fragments to each other for their original 3D reconstruction. Instead of the curvatures and torsions, the approach is based on establishing a local Cartesian coordinate at every point of the 3D contour curves. First of all, the 3D meshes of the fragments are acquired by a structure-light based method, with the corresponding 3D contour curves extracted from the outer boundaries. Then, the contour curves are matched and aligned to each other by estimating all the possible 3D rigid transformations of the curve pairs with our defined local Cartesian coordinates, and then the maximum likelihood rigid transformations are selected. Finally, a global refinement is introduced to adjust the alignment errors and improve the final reassembling accuracy. In addition, experiments with two groups of fragments suggest that this approach cannot only match and align fragments effectively, but also improve the accuracy significantly. Comparing with the original 3D model acquired before being broken, the final reassembling accuracy reaches 0.47 mm.

scholarly journals 3D IMAGE BASED GEOMETRIC DOCUMENTATION OF THE TOWER OF WINDS

2016 ◽  
Vol XLI-B5 ◽  
pp. 969-975
Author(s):  
M. S. Tryfona ◽  
A. Georgopoulos
Keyword(s):  
Point Cloud ◽  
3D Model ◽  
Vertical Section ◽  
Three Dimensional ◽  
Horizontal Section ◽  
Extreme Caution ◽  
Cartesian Coordinate ◽  
Data Acquisition And Processing ◽  
Selection Of ◽  
At Will

This paper describes and investigates the implementation of almost entirely image based contemporary techniques for the three dimensional geometric documentation of the Tower of the Winds in Athens, which is a unique and very special monument of the Roman era. These techniques and related algorithms were implemented using a well-known piece of commercial software with extreme caution in the selection of the various parameters. Problems related to data acquisition and processing, but also to the algorithms and to the software implementation are identified and discussed. The resulting point cloud has been georeferenced, i.e. referenced to a local Cartesian coordinate system through minimum geodetic measurements, and subsequently the surface, i.e. the mesh was created and finally the three dimensional textured model was produced. In this way, the geometric documentation drawings, i.e. the horizontal section plans, the vertical section plans and the elevations, which include orthophotos of the monument, can be produced at will from that 3D model, for the complete geometric documentation. Finally, a 3D tour of the Tower of the Winds has also been created for a more integrated view of the monument. The results are presented and are evaluated for their completeness, efficiency, accuracy and ease of production.

scholarly journals 3D IMAGE BASED GEOMETRIC DOCUMENTATION OF THE TOWER OF WINDS

2016 ◽  
Vol XLI-B5 ◽  
pp. 969-975 ◽  
Author(s):  
M. S. Tryfona ◽  
A. Georgopoulos
Keyword(s):  
Point Cloud ◽  
3D Model ◽  
Vertical Section ◽  
Three Dimensional ◽  
Horizontal Section ◽  
Extreme Caution ◽  
Cartesian Coordinate ◽  
Data Acquisition And Processing ◽  
Selection Of ◽  
At Will

This paper describes and investigates the implementation of almost entirely image based contemporary techniques for the three dimensional geometric documentation of the Tower of the Winds in Athens, which is a unique and very special monument of the Roman era. These techniques and related algorithms were implemented using a well-known piece of commercial software with extreme caution in the selection of the various parameters. Problems related to data acquisition and processing, but also to the algorithms and to the software implementation are identified and discussed. The resulting point cloud has been georeferenced, i.e. referenced to a local Cartesian coordinate system through minimum geodetic measurements, and subsequently the surface, i.e. the mesh was created and finally the three dimensional textured model was produced. In this way, the geometric documentation drawings, i.e. the horizontal section plans, the vertical section plans and the elevations, which include orthophotos of the monument, can be produced at will from that 3D model, for the complete geometric documentation. Finally, a 3D tour of the Tower of the Winds has also been created for a more integrated view of the monument. The results are presented and are evaluated for their completeness, efficiency, accuracy and ease of production.

scholarly journals A Noniterative Simultaneous Rigid Registration Method for Serial Sections of Biological Tissues

2020 ◽  
Vol 10 (3) ◽  
pp. 1156
Author(s):  
Chang Shu ◽  
Lin-Lin Li ◽  
Guoqing Li ◽  
Xi Chen ◽  
Hua Han
Keyword(s):  
Serial Section ◽  
Biological Tissues ◽  
Serial Sections ◽  
Extra Condition ◽  
Registration Method ◽  
Simultaneous Registration ◽  
Error Accumulation ◽  
Rigid Transformations ◽  
Short Time ◽  
Speed And Accuracy

In this paper, we propose a novel noniterative algorithm to simultaneously estimate optimal rigid transformations for serial section images, which is a key component in performing volume reconstructions of serial sections of biological tissue. To avoid the error accumulation and propagation caused by current algorithms, we add an extra condition: that the positions of the first and last section images should remain unchanged. This constrained simultaneous registration problem has not previously been solved. Our solution is noniterative; thus, it can simultaneously compute rigid transformations for a large number of serial section images in a short time. We demonstrate that our algorithm obtains optimal solutions under ideal conditions and shows great robustness under nonideal circumstances. Further, we experimentally show that our algorithm outperforms state-of-the-art methods in terms of speed and accuracy.

scholarly journals Detail-Preserving Shape Unfolding

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1187
Author(s):  
Bin Liu ◽  
Weiming Wang ◽  
Jun Zhou ◽  
Bo Li ◽  
Xiuping Liu
Keyword(s):  
Computer Graphics ◽  
Computational Efficiency ◽  
Local Structure ◽  
3D Model ◽  
State Of The Art ◽  
Geometric Distortion ◽  
Shape Deformation ◽  
3D Shape ◽  
Rigid Transformations ◽  
Iteration Processes

Canonical extrinsic representations for non-rigid shapes with different poses are preferable in many computer graphics applications, such as shape correspondence and retrieval. The main reason for this is that they give a pose invariant signature for those jobs, which significantly decreases the difficulty caused by various poses. Existing methods based on multidimentional scaling (MDS) always result in significant geometric distortions. In this paper, we present a novel shape unfolding algorithm, which deforms any given 3D shape into a canonical pose that is invariant to non-rigid transformations. The proposed method can effectively preserve the local structure of a given 3D model with the regularization of local rigid transform energy based on the shape deformation technique, and largely reduce geometric distortion. Our algorithm is quite simple and only needs to solve two linear systems during alternate iteration processes. The computational efficiency of our method can be improved with parallel computation and the robustness is guaranteed with a cascade strategy. Experimental results demonstrate the enhanced efficacy of our algorithm compared with the state-of-the-art methods on 3D shape unfolding.

Maximum Likelihood for Social Science

2018 ◽  
Author(s):  
Michael D. Ward ◽  
John S. Ahlquist
Keyword(s):  
Maximum Likelihood ◽  
Social Science

Das Kommunikationskompetenz-Inventar für Schulleitungen (KKI-SL)

Diagnostica ◽  
2017 ◽  
Vol 63 (3) ◽  
pp. 179-192 ◽  
Author(s):  
Helen Hertzsch
Keyword(s):  
Maximum Likelihood

Zusammenfassung. Gegenstand der vorliegenden Studien ist die Konstruktion und Validierung eines deutschsprachigen Inventars zur Erfassung des Konstrukts Kommunikationskompetenz von Schulleitungen (KKI-SL). Kommunikationskompetenz wird als dreidimensionales Konstrukt (Wissen, Fähigkeiten, Motivation) konzeptualisiert und in ein theoretisches Rahmenmodell eingebettet. Fünf Studien wurden mit deutschen Lehrkräften aller Schularten durchgeführt: Selektion und Kategorisierung der Items via Experten-Rating sowie Exploration der Dimensionalität (N = 169), Kreuzvalidierung der gefundenen Faktorenstruktur (N = 1 354), Test-Retest-Reliabilität (N = 126), konvergente und diskriminante Validität (N = 331) und Kriterienrelevanz (N = 1 023). Itemanalysen und Maximum Likelihood-Faktorenanalysen führten zu einer 3-Faktoren-Lösung (Alterzentrismus, Kommunikationswissen und -bereitschaft, Selbstregulationsfähigkeit) mit guten internen Konsistenzen. Konfirmatorische Faktorenanalysen bestätigten die Struktur mit 14 Items. Die psychometrischen Kennwerte des Inventars waren durchweg gut. Beziehungen zu korrespondierenden Konstrukten belegen die konvergente und divergente Validität des Instruments. Als weiterer Validitätshinweis konnten Zusammenhänge mit relevanten Ergebniskriterien (z. B. Arbeitszufriedenheit) nachgewiesen werden.

Intrafamiliäre Ähnlichkeit von Physischer Anhedonie, Wahrnehmungsabweichungen und Magischem Denken

1999 ◽  
Vol 28 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Thomas D. Meyer ◽  
Martin Hautzinger
Keyword(s):  
Maximum Likelihood ◽  
Sich Eine

Zusammenfassung. Das Ziel der vorliegenden Arbeit besteht darin, durch die Untersuchung des Phänomens der familiären Häufung in Form von intrafamiliären Korrelationen einen Beitrag zur Validität der Schizotypie-Skalen Physische Anhedonie (PA), Wahrnehmungsabweichungen (PAB) und Magisches Denken (MI) zu leisten. 279 Personen und ihren Angehörigen ersten Grades wurden die Schizotypie-Skalen PA, PAB und MI zugeschickt. Die Korrelationen wurden mit Hilfe der Maximum-Likelihood-Methode geschätzt. Für PA und MI fanden sich substantielle Korrelationen zwischen Eltern und ihren Nachkommen, aber keine Ähnlichkeit zwischen den Geschwistern. Bei PAB zeigte sich eine marginale Beziehung zwischen den Werten der Geschwister, aber keine Korrelation zu den Eltern. In allen drei Skalen fanden sich jedoch bedeutsame Korrelationen zwischen den Eltern. Keine Hinweise auf intrafamiliäre Ähnlichkeit bezüglich verschiedener Schizotypie-Indikatoren fanden sich in Form von interindividuellen Kreuzkorrelationen. Die Ergebnisse und ihre theoretische Relevanz werden im Rahmen der bislang existierenden Befundlage zur intrafamiliären Ähnlichkeit bei Schizotypie diskutiert.

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