A framework for digital sunken relief generation based on 3D geometric models

Sunken relief is a special art form of sculpture whereby the depicted shapes are sunk into a given surface. This is traditionally created by laboriously carving materials such as stone. Sunken reliefs often utilize the engraved lines or strokes to strengthen the impressions of a 3D presence and to highlight the features which otherwise are unrevealed. In other types of reliefs, smooth surfaces and their shadows convey such information in a coherent manner. Existing methods for relief generation are focused on forming a smooth surface with a shallow depth which provides the presence of 3D figures. Such methods unfortunately do not help the art form of sunken reliefs as they omit the presence of feature lines. We propose a framework to produce sunken reliefs from a known 3D geometry, which transforms the 3D objects into three layers of input to incorporate the contour lines seamlessly with the smooth surfaces. The three input layers take the advantages of the geometric information and the visual cues to assist the relief generation. This framework alters existing techniques in line drawings and relief generation, and then combines them organically for this particular purpose

Regularized multiframe phase-shifting algorithm for three-dimensional profilometry

In many industrial inspection systems, it is required to have a high-precision three-dimensional measurement of an object under test. A popular technique is phase-measuring profilometry. In this paper, we develop some phase-shifting algorithms (PSAs). We propose a novel smoothness constraint in a regularization framework; we call this the R-PSA method and show how to obtain the desired phase measure with an iterative procedure. Both the simulation and experimental results verify the efficacy of our algorithm compared with current multiframe PSAs for interferometric measurements.published_or_final_versio

Improving shape from shading with interactive Tabu search

Optimisation based shape from shading (SFS) is sensitive to initialization: errors in initialization are a significant cause of poor overall shape reconstruction. In this paper, we present a method to help overcome this problem by means of user interaction. There are two key elements in our method. Firstly, we extend SFS to consider a set of initializations, rather than to use a single one. Secondly, we efficiently explore this initialization space using a heuristic search method, tabu search, guided by user evaluation of the reconstruction quality. Reconstruction results on both synthetic and real images demonstrate the effectiveness of our method in providing more desirable shape reconstructions

Computer Assisted Relief Generation - a Survey

In this paper we present an overview of the achievements accomplished to date in the field of computer aided relief generation. We delineate the problem, classify the different solutions, analyze similarities, investigate the evelopment and review the approaches according to their particular relative strengths and weaknesses. In consequence this survey is likewise addressed to researchers and artists through providing valuable insights into the theory behind the different concepts in this field and augmenting the options available among the methods presented with regard to practical application

3D digital relief generation.

This thesis investigates a framework for generating reliefs. Relief is a special kind of sculptured artwork consisting of shapes carved on a surface so as to stand out from the surrounding background. Traditional relief creation is done by hand and is therefore a laborious process. In addition, hand-made reliefs are hard to modify. Contrasted with this, digital relief can offer more flexibility as well as a less laborious alternative and can be easily adjusted. This thesis reviews existing work and offers a framework to tackle the problem of generating three types of reliefs: bas reliefs, high reliefs and sunken reliefs. Considerably enhanced by incorporating gradient operations, an efficient bas relief generation method has been proposed, based on 2D images. An improvement of bas relief and high relief generation method based on 3D models has been provided as well, that employs mesh representation to process the model. This thesis is innovative in describing and evaluating sunken relief generation techniques. Two types of sunken reliefs have been generated: one is created with pure engraved lines, and the other is generated with smooth height transition between lines. The latter one is more complex to implement, and includes three elements: a line drawing image provides a input for contour lines; a rendered Lambertian image shares the same light direction of the relief and sets the visual cues and a depth image conveys the height information. These three elements have been combined to generate final sunken reliefs. It is the first time in computer graphics that a method for digital sunken relief generation has been proposed. The main contribution of this thesis is to have proposed a systematic framework to generate all three types of reliefs. Results of this work can potentially provide references for craftsman, and this work could be beneficial for relief creation in the fields of both entertainment and manufacturing

Yüz anotomisine dayalı ifade tanıma

Literatürde sunulan geometriye dayalı yüz ifadesi tanıma algoritmaları çoğunlukla araştırmacılar tarafından seçilen nirengi noktalarının devinimlerine veya yüz ifadesi kodlama sistemi (FACS) tarafından tanımlanan eylem birimlerinin etkinlik derecelerine odaklanır. Her iki yaklaşımda da nirengi noktaları, ifadenin en yoğun gözlemlendiği dudak, burun kenarları ve alın üzerinde konumlandırılır. Farklı kas etkinlikleri, birden fazla kasın etki alanında bulunan bu nirengi noktaları üzerinde benzer devinimlere neden olurlar. Bu nedenle, karmaşık ifadelerin belli noktalara konulan, sınırlı sayıdaki nirengi ile analizi oldukça zordur. Bu projede, yüz üzerinde kas etkinlik alanlarına dağıtılmış çok sayıda nirengi nokta-sının yüz ifadesinin oluşturulması sürecinde izlenmesi ile kas etkinlik derecelerinin belirlenmesini önerdik. Önerdiğimiz yüz ifadesi tanıma algoritması altı aşama içerir; (1) yüz modelinin deneğin yüzüne uyarlanması, (2) herhangi bir kasın etki alanında bulunan tüm nirengi noktalarının imge dizisinin ardışık çerçevelerinde izlenmesi, (3) baş yöneliminin belirlenmesi ve yüz modelinin imge üzerinde gözlemlenen yüz ile hizalanması, (4) yüze ait nirengi noktalarının deviniminden yola çıkarak model düğümlerinin yeni koordinatlarının kestirimi, (5) düğüm devinimlerinin kas kuvvetleri için çözülmesi, ve (6) elde edilen kas kuvvetleri ile yüz ifadesi sınıflandırılmasının yapılması. Algoritmamız, modelin yüze uyarlanması aşamasında yüz imgesi üzerinde nirengi noktalarının seçilmesi haricinde tamamen otomatiktir. Kas etkinliğine dayalı bu öznitelikleri temel ve belirsiz ifadelerin sınıflandırılması problemlerinde sınadık. Yedi adet temel yüz ifadesi üzerinde SVM sınıflandırıcısı ile %76 oranında başarı elde ettik. Bu oran, insanların ifade tanımadaki yetkinliklerine yakındır. Yedi temel ifadenin belirsiz gözlemlendiği çerçevelerde en yüksek başarıyı yine SVM sınıflandırıcısı ile %55 olarak elde ettik. Bu başarım, kas kuvvetlerinin genellikle hafif ve ani görülen istemsiz ifadelerin seziminde de başarılı olabileceğini göstermektedir. Kas kuvvetleri, yüz ifadesinin oluşturulmasındaki temel fiziksel gerçekliği yansıtan özniteliklerdir. Kas etkinliklerinin hassasiyetle kestirimi, belirsiz ifade değişikliklerinin sezimini sağladığı gibi, karmaşık yüz ifadelerinin sınıflandırılmalarını kolaylaştıracaktır. Ek olarak, araştırmacılar veya uzmanlar tarafından seçilen nirengi devinimleri ile kısıtlı kal-mayan bu yaklaşım, duygular ve yüz ifadeleri arasında bilinmeyen bağıntıların ortaya çıkarılmasını sağlayabilecektir.The geometric approaches to facial expression recognition commonly focus on the displa-cement of feature points that are selected by the researchers or the action units that aredefined by the facial action coding system (FACS). In both approaches the feature pointsare carefully located on lips, nose and the forehead, where an expression is observed at itsfull strength. Since these regions are under the influence of multiple muscles, distinct mus-cular activities could result in similar displacements of the feature points. Hence, analysisof complex expressions through a set of specific feature points is quite difficult.In this project we propose to extract the facial muscle activity levels through multiplepoints distributed over the muscular regions of influence. The proposed algorithm consistsof; (1) semi–automatic customization of the face model to a subject, (2) identification andtracking of facial features that reside in the region of influence of a muscle, (3) estimationof head orientation and alignment of the face model with the observed face, (4) estima-tion of relative displacements of vertices that produce facial expressions, (5) solving vertexdisplacements to obtain muscle forces, and (6) classification of facial expression with themuscle force features. Our algorithm requires manual intervention only in the stage ofmodel customization.We demonstrate the representative power of the proposed muscle–based features onclassification problems of seven basic and subtle expressions. The best performance onthe classification problem of basic expressions was 76%, obtained by use of SVM. Thisresult is close to the performance of humans in facial expression recognition. Our bestperformance for classification of seven subtle expressions was %55, once again by use ofSVM. This figure implies that muscle–based features are good candidates for involuntaryexpressions, which are often subtle and instantaneous.Muscle forces can be considered as the ultimate base functions that anatomicallycompose all expressions. Increased reliability in extraction of muscle forces will enabledetection and classification of subtle and complex expressions with higher precision. Mo-reover, the proposed algorithm may be used to reveal unknown mechanisms of emotionsand expressions as it is not limited to a predefined set of heuristic features.TÜBİTA

Of assembling small sculptures and disassembling large geometry

This thesis describes the research results and contributions that have been achieved during the author’s doctoral work. It is divided into two independent parts, each of which is devoted to a particular research aspect. The first part covers the true-to-detail creation of digital pieces of art, so-called relief sculptures, from given 3D models. The main goal is to limit the depth of the contained objects with respect to a certain perspective without compromising the initial three-dimensional impression. Here, the preservation of significant features and especially their sharpness is crucial. Therefore, it is necessary to overemphasize fine surface details to ensure their perceptibility in the more complanate relief. Our developments are aimed at amending the flexibility and user-friendliness during the generation process. The main focus is on providing real-time solutions with intuitive usability that make it possible to create precise, lifelike and aesthetic results. These goals are reached by a GPU implementation, the use of efficient filtering techniques, and the replacement of user defined parameters by adaptive values. Our methods are capable of processing dynamic scenes and allow the generation of seamless artistic reliefs which can be composed of multiple elements. The second part addresses the analysis of repetitive structures, so-called symmetries, within very large data sets. The automatic recognition of components and their patterns is a complex correspondence problem which has numerous applications ranging from information visualization over compression to automatic scene understanding. Recent algorithms reach their limits with a growing amount of data, since their runtimes rise quadratically. Our aim is to make even massive data sets manageable. Therefore, it is necessary to abstract features and to develop a suitable, low-dimensional descriptor which ensures an efficient, robust, and purposive search. A simple inspection of the proximity within the descriptor space helps to significantly reduce the number of necessary pairwise comparisons. Our method scales quasi-linearly and allows a rapid analysis of data sets which could not be handled by prior approaches because of their size.Die vorgelegte Arbeit beschreibt die wissenschaftlichen Ergebnisse und Beiträge, die während der vergangenen Promotionsphase entstanden sind. Sie gliedert sich in zwei voneinander unabhängige Teile, von denen jeder einem eigenen Forschungsschwerpunkt gewidmet ist. Der erste Teil beschäftigt sich mit der detailgetreuen Erzeugung digitaler Kunstwerke, sogenannter Reliefplastiken, aus gegebenen 3D-Modellen. Das Ziel ist es, die Objekte, abhängig von der Perspektive, stark in ihrer Tiefe zu limitieren, ohne dass der Eindruck der räumlichen Ausdehnung verloren geht. Hierbei kommt dem Aufrechterhalten der Schärfe signifikanter Merkmale besondere Bedeutung zu. Dafür ist es notwendig, die feinen Details der Objektoberfläche überzubetonen, um ihre Sichtbarkeit im flacheren Relief zu gewährleisten. Unsere Weiterentwicklungen zielen auf die Verbesserung der Flexibilität und Benutzerfreundlichkeit während des Enstehungsprozesses ab. Der Fokus liegt dabei auf dem Bereitstellen intuitiv bedienbarer Echtzeitlösungen, die die Erzeugung präziser, naturgetreuer und visuell ansprechender Resultate ermöglichen. Diese Ziele werden durch eine GPU-Implementierung, den Einsatz effizienter Filtertechniken sowie das Ersetzen benutzergesteuerter Parameter durch adaptive Werte erreicht. Unsere Methoden erlauben das Verarbeiten dynamischer Szenen und die Erstellung nahtloser, kunstvoller Reliefs, die aus mehreren Elementen und Perspektiven zusammengesetzt sein können. Der zweite Teil behandelt die Analyse wiederkehrender Stukturen, sogenannter Symmetrien, innerhalb sehr großer Datensätze. Das automatische Erkennen von Komponenten und deren Muster ist ein komplexes Korrespondenzproblem mit zahlreichen Anwendungen, von der Informationsvisualisierung über Kompression bis hin zum automatischen Verstehen. Mit zunehmender Datenmenge geraten die etablierten Algorithmen an ihre Grenzen, da ihre Laufzeiten quadratisch ansteigen. Unser Ziel ist es, auch massive Datensätze handhabbar zu machen. Dazu ist es notwendig, Merkmale zu abstrahieren und einen passenden niedrigdimensionalen Deskriptor zu entwickeln, der eine effiziente, robuste und zielführende Suche erlaubt. Eine simple Betrachtung der Nachbarschaft innerhalb der Deskriptoren hilft dabei, die Anzahl notwendiger paarweiser Vergleiche signifikant zu reduzieren. Unser Verfahren skaliert quasi-linear und ermöglicht somit eine rasche Auswertung auch auf Daten, die für bisherige Methoden zu groß waren

Interactive shape from shading

Shape from shading (SfS) has always been difficult for real applications due to its intrinsic ill-posedness. In this paper, we propose an interactive SfS method which efficiently uses human knowledge in order to resolve ambiguity. We propose a global solution of continuous surfaces with a few constraints of surface normals that are interactively imposed to regularize the problem. A surface is divided into local patches, and each local solution is estimated with a fast marching SfS. It is shown that the boundaries of local solutions constitute a weighted Voronoi diagram, which allows for the formation of a global solution from the local ones. Finally, we optimize this global estimation by minimizing an energy functional based on shading and smoothness priors. Reconstruction results from both synthetic and real images demonstrate the usability of the new approach for various modeling applications