Constrained random sampling and gap filling technique for near-regular texture synthesis

Projecte realitzat mitjançant programa de mobilitat. TECHNISCHE UNIVERSITÄT BERLIN. FAKULTÄT ELEKTROTECHNIK UND INFORMATIK. INSTITUT FÜR TECHNISCHE INFORMATIK UND MIKROELEKTRONIK COMPUTER VISION AND REMOTE SENSINGThis thesis addresses the synthesis of near-regular textures, i.e. textures that consist of a regular global structure plus subtle yet very characteristic stochastic irregularities, from a small exemplar image. Such textures are difficult to synthesize due to the complementary characteristics of these structures. The main purpose of this thesis is to present a novel method which we call Random Sampling and Gap Filling (RSGF) to synthesize near-regular textures. The synthesis approach is guided by a lattice of the global structure estimated from a generalized normalized autocorrelation of the sample image. This lattice constrains a random sampling process to maintain the global regular structure yet ensuring the characteristic randomness of the irregular structures. An alternative method to find the piece of texture within the input sample whose simple tiling presents less visible seams is also presented for illustration of quality enhancement purposes. Results presented in this work show that our method does not only produce convincing results for regular or near-regular textures but also for irregular textures

Around the Domino Problem – Combinatorial Structures and Algebraic Tools

Given a finite set of square tiles, the domino problem is the question of whether is it possible to tile the plane using these tiles. This problem is known to be undecidable in the planar case, and is strongly linked to the question of the periodicity of the tiling. In this thesis we look at this problem in two different ways: first, we look at the particular case of low complexity tilings and second we generalize it to more general structures than the plane, groups. A tiling of the plane is said of low complexity if there are at most mn rectangles of size m × n appearing in it. Nivat conjectured in 1997 that any such tiling must be periodic, with the consequence that the domino problem would be decidable for low complexity tilings. Using algebraic tools introduced by Kari and Szabados, we prove a generalized version of Nivat’s conjecture for a particular class of tilings (a subclass of what is called of algebraic subshifts). We also manage to prove that Nivat’s conjecture holds for uniformly recurrent tilings, with the consequence that the domino problem is indeed decidable for low-complexity tilings. The domino problem can be formulated in the more general context of Cayley graphs of groups. In this thesis, we develop new techniques allowing to relate the Cayley graph of some groups with graphs of substitutions on words. A first technique allows us to show that there exists both strongly periodic and weakly-but-not-strongly aperiodic tilings of the Baumslag-Solitar groups BS(1, n). A second technique is used to show that the domino problem is undecidable for surface groups. Which provides yet another class of groups verifying the conjecture saying that the domino problem of a group is decidable if and only if the group is virtually free

The evolution of a craft: Post-Byzantine bookbinding between the late fifteenth and the early eighteenth century from the libraries of the Iviron Monastery in Mount Athos/Greece and the St. Catherine's monastery in Sinai/Egypt.

The thesis investigates the ways through which the Greek-style bookbinding was gradually supplanted by European bookbinding, a process which occurred between the late fifteenth century, after the fall of the Byzantine Empire, and the early eighteenth century. The Greek-style bookbinding is a distinctive typological binding structure confined in the milieu of the Byzantine and post-Byzantine civilization. The research is based on two major monastic libraries, those of the Iviron monastery in Mount Athos/Greece and of the St. Catherine's monastery in Sinai/Egypt. The primary material of the research consists of a detailed survey of 419 bookbindings dated between the late fifteenth and the early eighteenth century. To collect and store the collected data a survey methodology had to be devised and a computer database appositely built. Through the analysis of the collected data twelve major bookbinding ateliers are identified and described in full detail, representing both monastic communities, providing the most extensive body of information on bindings of the Greek-Orthodox Christian monastic communities so far. It is through the description of these ateliers that the various influences, both from the West and the East, under which the aforementioned evolution occurred, are identified, considered, and interpreted. A statistical analysis is provided at the end of the thesis using tables and graphics in the effort to illustrate the major changes in time and space of the most significant bookbinding features, both technical and decorative. Except providing a full photographic survey of the bookbindings described in the examination of twelve different bookbinding ateliers, graphic representations of many technical and decorative features, and a complete indexed list of all the 593 decorative motifs recorded, the thesis also tries to explore, whenever possible, how these bookbindings reflect the social, religious and commercial life of the time. Since there is only little, isolated and dispersed, information published, and practically no systematic research on this specific subject and for the specific period considered here, the thesis aims to contribute in filling in a gap as well as providing a methodology for further research in the subject

A system for image-based modeling and photo editing

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Architecture, 2002.Includes bibliographical references (p. 169-178).Traditionally in computer graphics, a scene is represented by geometric primitives composed of various materials and a collection of lights. Recently, techniques for modeling and rendering scenes from a set of pre-acquired images have emerged as an alternative approach, known as image-based modeling and rendering. Much of the research in this field has focused on reconstructing and rerendering from a set of photographs, while little work has been done to address the problem of editing and modifying these scenes. On the other hand, photo-editing systems, such as Adobe Photoshop, provide a powerful, intuitive, and practical means to edit images. However, these systems are limited by their two-dimensional nature. In this thesis, we present a system that extends photo editing to 3D. Starting from a single input image, the system enables the user to reconstruct a 3D representation of the captured scene, and edit it with the ease and versatility of 2D photo editing. The scene is represented as layers of images with depth, where each layer is an image that encodes both color and depth. A suite of user-assisted tools are employed, based on a painting metaphor, to extract layers and assign depths. The system enables editing from different viewpoints, extracting and grouping of image-based objects, and modifying the shape, color, and illumination of these objects. As part of the system, we introduce three powerful new editing tools. These include two new clone brushing tools: the non-distorted clone brush and the structure-preserving clone brush. They permit copying of parts of an image to another via a brush interface, but alleviate distortions due to perspective foreshortening and object geometry.(cont.) The non-distorted clone brush works on arbitrary 3D geometry, while the structure-preserving clone brush, a 2D version, assumes a planar surface, but has the added advantage of working directly in 2D photo-editing systems that lack depth information. The third tool, a texture-illuminance decoupling filter, discounts the effect of illumination on uniformly textured areas by decoupling large- and small-scale features via bilateral filtering. This tool is crucial for relighting and changing the materials of the scene. There are many applications for such a system, for example architectural, lighting and landscape design, entertainment and special effects, games, and virtual TV sets. The system allows the user to superimpose scaled architectural models into real environments, or to quickly paint a desired lighting scheme of an interior, while being able to navigate within the scene for a fully immersive 3D experience. We present examples and results of complex architectural scenes, 360-degree panoramas, and even paintings, where the user can change viewpoints, edit the geometry and materials, and relight the environment.by Byong Mok Oh.Ph.D

Querying and creating visualizations by analogy

Journal ArticleWhile there have been advances in visualization systems, particularly in multi-view visualizations and visual exploration, the process of building visualizations remains a major bottleneck in data exploration. We show that provenance metadata collected during the creation of pipelines can be reused to suggest similar content in related visualizations and guide semi-automated changes. We introduce the idea of query-by-example in the context of an ensemble of visualizations, and the use of analogies as first-class operations in a system to guide scalable interactions. We describe an implementation of these techniques in VisTrails, a publicly-available, open-source system

Braids via term rewriting

We present a brief introduction to braids, in particular simple positive braids, with a double emphasis: first, we focus on term rewriting techniques, in particular, reduction diagrams and decreasing diagrams. The second focus is our employment of the colored braid notation next to the more familiar Artin notation. Whereas the latter is a relative, position dependent, notation, the former is an absolute notation that seems more suitable for term rewriting techniques such as symbol tracing. Artin's equations translate in this notation to simple word inversions. With these points of departure we treat several basic properties of positive braids, in particular related to the word problem, confluence property, projection equivalence, and the congruence property. In our introduction the beautiful diamond known as the permutohedron plays a decisive role