scholarly journals IMPROVED CONJUGATE GRADIENT BUNDLE ADJUSTMENT OF DUNHUANG WALL PAINTING IMAGES

2017 ◽  
Vol IV-2/W4 ◽  
pp. 213-218
Author(s):  
K. Hu ◽  
X. Huang ◽  
H. You
Keyword(s):  
Conjugate Gradient ◽  
Coefficient Matrix ◽  
Wall Painting ◽  
Bundle Adjustment ◽  
Cholesky Factorization ◽  
Normal Equation ◽  
Wall Paintings ◽  
Incomplete Cholesky Factorization ◽  
Preconditioning Method ◽  
Actual Accuracy

Bundle adjustment with additional parameters is identified as a critical step for precise orthoimage generation and 3D reconstruction of Dunhuang wall paintings. Due to the introduction of self-calibration parameters and quasi-planar constraints, the structure of coefficient matrix of the reduced normal equation is banded-bordered, making the solving process of bundle adjustment complex. In this paper, Conjugate Gradient Bundle Adjustment (CGBA) method is deduced by calculus of variations. A preconditioning method based on improved incomplete Cholesky factorization is adopt to reduce the condition number of coefficient matrix, as well as to accelerate the iteration rate of CGBA. Both theoretical analysis and experimental results comparison with conventional method indicate that, the proposed method can effectively conquer the ill-conditioned problem of normal equation and improve the calculation efficiency of bundle adjustment with additional parameters considerably, while maintaining the actual accuracy.

scholarly journals Fast kernel k-means clustering using incomplete Cholesky factorization

2021 ◽  
Vol 402 ◽  
pp. 126037
Author(s):  
Li Chen ◽  
Shuisheng Zhou ◽  
Jiajun Ma ◽  
Mingliang Xu
Keyword(s):  
Cholesky Factorization ◽  
Incomplete Cholesky Factorization

Wall paintings – diagnostic and archaeometric studies

2018 ◽  
Vol 4 (4) ◽  
Author(s):  
Susanna Bracci ◽  
Giovanni Bartolozzi
Keyword(s):  
Case Studies ◽  
Recent Literature ◽  
Wall Painting ◽  
Wall Paintings

Abstract The paper deals with the techniques and protocols used for studying wall paintings. A brief introduction about the more recent literature dealing with archaeometric and diagnostic analyses of wall paintings is reported. After that, the illustration of three case studies, spanning from Roman to contemporary wall painting are described.

scholarly journals Stratigraphy of the wall paintings in the main church of the Praskvica Monastery

Zograf ◽  
2014 ◽  
pp. 153-163
Author(s):  
Dragan Vojvodic
Keyword(s):  
Seventeenth Century ◽  
Sixteenth Century ◽  
Wall Painting ◽  
The Other ◽  
Stylistic Analysis ◽  
Wall Paintings ◽  
The West ◽  
The Third ◽  
Technical Features ◽  
The Church

In the katholikon of the monastery of Praskvica there are remains of two layers of post-Byzantine wall-painting: the earlier, from the third quarter of the sixteenth century, and later, from the first half of the seventeenth century, which is the conclusion based on stylistic analysis and technical features. The portions of frescoes belonging to one or the other layer can be clearly distinguished from one another and the content of the surviving representations read more thoroughly than before. It seems that the remains of wall-painting on what originally was the west facade of the church also belong to the earlier layer. It is possible that the church was not frescoed in the lifetime of its ktetor, Balsa III Balsic.

scholarly journals MODERN METHODS OF BUNDLE ADJUSTMENT ON THE GPU

2016 ◽  
Vol III-3 ◽  
pp. 43-50 ◽  
Author(s):  
R. Hänsch ◽  
I. Drude ◽  
O. Hellwich
Keyword(s):  
Conjugate Gradient ◽  
Gradient Descent ◽  
Optimization Problem ◽  
Error Rates ◽  
Bundle Adjustment ◽  
Test Cases ◽  
Current State ◽  
Marquardt Algorithm ◽  
Levenberg Marquardt ◽  
Nonlinear Conjugate Gradient

The task to compute 3D reconstructions from large amounts of data has become an active field of research within the last years. Based on an initial estimate provided by structure from motion, bundle adjustment seeks to find a solution that is optimal for all cameras and 3D points. The corresponding nonlinear optimization problem is usually solved by the Levenberg-Marquardt algorithm combined with conjugate gradient descent. While many adaptations and extensions to the classical bundle adjustment approach have been proposed, only few works consider the acceleration potentials of GPU systems. This paper elaborates the possibilities of time and space savings when fitting the implementation strategy to the terms and requirements of realizing a bundler on heterogeneous CPUGPU systems. Instead of focusing on the standard approach of Levenberg-Marquardt optimization alone, nonlinear conjugate gradient descent and alternating resection-intersection are studied as two alternatives. The experiments show that in particular alternating resection-intersection reaches low error rates very fast, but converges to larger error rates than Levenberg-Marquardt. PBA, as one of the current state-of-the-art bundlers, converges slower in 50 % of the test cases and needs 1.5-2 times more memory than the Levenberg- Marquardt implementation.

A CONSTRAINT PRECONDITIONER FOR SOLVING SYMMETRIC POSITIVE DEFINITE SYSTEMS AND APPLICATION TO THE HELMHOLTZ EQUATIONS AND POISSON EQUATIONS

2010 ◽  
Vol 15 (3) ◽  
pp. 299-311 ◽  
Author(s):  
Zhuo-Hong Huang ◽  
Ting-Zhu Huang
Keyword(s):  
Numerical Experiments ◽  
Positive Definite ◽  
Cholesky Factorization ◽  
Helmholtz Equations ◽  
Poisson Equations ◽  
Symmetric Positive Definite ◽  
Incomplete Cholesky Factorization ◽  
Preconditioned Matrix ◽  
Factorization Methods ◽  
Number Of Iterations

In this paper, first, by using the diagonally compensated reduction and incomplete Cholesky factorization methods, we construct a constraint preconditioner for solving symmetric positive definite linear systems and then we apply the preconditioner to solve the Helmholtz equations and Poisson equations. Second, according to theoretical analysis, we prove that the preconditioned iteration method is convergent. Third, in numerical experiments, we plot the distribution of the spectrum of the preconditioned matrix M−1A and give the solution time and number of iterations comparing to the results of [5, 19].

scholarly journals Investigation of the Optical, Physical, and Chemical Interactions between Diammonium Hydrogen Phosphate (DAP) and Pigments

2019 ◽  
Vol 11 (14) ◽  
pp. 3803 ◽  
Author(s):  
Xiao Ma ◽  
Hélène Pasco ◽  
Magdalena Balonis ◽  
Ioanna Kakoulli
Keyword(s):  
Wall Painting ◽  
Wall Paintings ◽  
Reaction Products ◽  
Hydrogen Phosphate ◽  
Chemical Interactions ◽  
Diammonium Hydrogen Phosphate ◽  
Red Lead ◽  
Physical And Chemical ◽  
Diammonium Hydrogen ◽  
Lapis Lazuli

This research investigates and evaluates the optical, physical, and chemical interactions between a diammonium hydrogen phosphate (DAP) solution and seven pigments commonly encountered in archaeological and historic fresco and secco wall paintings and polychrome monuments. The pigments include cinnabar, French ochre, chalk, lapis lazuli, raw sienna, burnt umber, and red lead. The raw pigments were analyzed before and after the interaction with the DAP solution, and the reaction products resulting from the contact of the pigments with the DAP solution were evaluated to obtain a comprehensive understanding of the effects of diammonium phosphate on the color, morphology, and chemical composition of the pigments. The results indicated no significant changes of the color or of the chemistry of cinnabar, French ochre, and lapis lazuli. Carbonate-containing primary and secondary (found as impurities in earth pigments) pigments, such as chalk and calcium carbonate, were transformed into calcium phosphate, though without a significant change in color. Phase and strong color changes occurred only for the red lead pigment, associated with the transformation of red lead into hydroxypyromorphite. These data established the parameters and identified the risks of the direct application of DAP solutions on pigments. Further research will be undertaken to assess the potential use of DAP as a consolidant of wall paintings and other polychrome surfaces through testing on wall painting/polychromy mockups and on-site archaeological/historic painted surfaces.

Water and stone: the economics of wall-painting in Pompeii (A.D. 62-79)

2019 ◽  
Vol 32 ◽  
pp. 97-128
Author(s):  
Francesca Bologna
Keyword(s):  
Experimental Archaeology ◽  
Wall Painting ◽  
Industrial Building ◽  
Wall Paintings ◽  
Economic Implications ◽  
Local Markets ◽  
Working Practices ◽  
Roman Wall Painting ◽  
The Creation

This article investigates production times, workforce, and materials involved in the creation of wall-paintings, applying figures obtained from pre-industrial building manuals and through experimental archaeology. This is a crucial yet — at least with regard to Roman wall-painting – unexploited avenue for research, one that has already been successfully applied to the study of ancient construction, stone-working, and mosaic production.1 The implications of this type of study are twofold: estimating labour figures allows us to assess painters’ working practices and workforce organization, yet it can also help uncover the burden sustained by patrons in both economic and personal terms, thereby providing a more realistic notion of what it meant to have one’s house decorated. Ultimately, this can lead to a better understanding of local markets and of the socio-economic implications of the wall-painting industry

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