On expert performance in 3D curve-drawing tasks

A study is described which examines the drawing accuracy of experts when drawing foreshortened projections of 3D curves in ecologically-valid conditions. The main result of this study is that the distribution of error in expert drawings exhibits a bias similar to that previously observed in non-expert subjects, which is dependent on the degree of foreshortening of the imagined drawing surface. A review of existing perceptual studies also finds that only absolute 2D image-space error has been considered, which has been found to be largest with viewing angles of 25-55 ◦. Our visualizations of 3D error indicate that 3D bias continues to increase with decreasing viewing angle. Based on these findings, we analyze current 3D curve drawing techniques for susceptibility to foreshortening bias, and make suggestions for future sketch-based modeling systems

A Sketching Interface for Garment Design

National audienceThe range of approaches used for clothing virtual characters is large: for incidental characters, the clothing may be no more than a texture map. For lead characters in feature films, full-fledged physical simulation of detailed cloth models may be used. And in the midrange, simple skinning techniques, combined with texture mapping, are common, providing some deformation of clothing as the character moves, but no physical realism. There are three problems one can associate with clothing virtual characters: the design of the clothes (tailoring), placing them on the character (dressing), and making them look physically correct (typically through simulation). The process of tailoring involves choosing the cloth and fitting it to the body, often making adjustments in the patterns of the cloth to adapt it to the particular person's body shape, and then sewing it. For virtual characters, clothing often has no "patterns" from which it is sewn, instead it is represented by a simple polygonal mesh that is constructed to fit the body. It's currently tedious to construct such meshes even without the issues of patterns and stitching. It's sometimes done by directly incorporating the cloth mesh into a character's geometric model, so that the character doesn't actually have legs, for instance, but just pants (see figure 1.1). In this case physical simulation is no longer a possibility, and when a character needs new clothes, it must be largely re-modeled. An alternative approach involves drawing pattern pieces for a garment and positioning them over the naked form of the character, defining stitching constraints, etc. This can be tedious, especially when the character is not important enough to merit this amount of effort; it also requires an understanding of how cloth fits over shapes, although the actual pattern-and-stitching information may not be relevant after the tailoring is completed (except in the rare case where the physical properties of the cloth -- was it cut on the bias? Does the cloth resist folding along one axis? -- are later used in a full-fledged physical simulation). Our approach combines tailoring and dressing into a single step to create a mesh that's suitable for later simulation or skinning approaches. The idea is to make it easy to generate simple garments that are adapted to an existing model. We believe that most people know better how to draw garments than the patterns which are needed to sew them. The aim of this work is thus to explore the use of a sketch-based interface for quickly constructing 3D virtual garments over a character model. This report describes simple solutions to the problems of shape generation and placement of the clothing. The resulting system is so easy to use that it takes only few minutes to create a simple garment

Sketch-based path design

We first present a novel approach to sketching 2D curves with minimally varying curvature as piecewise clothoids. A stable and efficient algorithm fits a sketched piecewise linear curve using a number of clothoid segments with G2 continuity based on a specified error tolerance. We then present a system for conceptually sketching 3D layouts for road and other path networks. Our system makes four key contributions. First, we generate paths with piecewise linear curvature by fitting 2D clothoid curves to strokes sketched on a terrain. Second, the height of paths above the terrain is automatically determined using a new constraint optimization formulation of the occlusion relationships between sketched strokes. Third, we present the break-out lens, a novel widget inspired by break-out views used in engineering visualization, to facilitate the in-context and interactive manipulation of paths from alternate view points. Finally, our path construction is terrain sensitive. ii Acknowledgements I would like to acknowledge the efforts of my supervisor, Karan Singh, and thank him for his guidance over the duration of the Masters program. I learned much from him a

Set-Based User Interaction

This work demonstrates specific ways that the design of computer user interfaces can influence how individuals structure the problem solving process. In particular, an observational study of expert users of an image manipulation application indicates that current user interfaces make it difficult to explore sets of alternatives in parallel, despite this being a common problem solving practice. As a consequence, individuals tend to engage in highly linear problem solving processes. To address this problem, this work introduces the concept of a set-based interface, or an interface that facilitates the generation, manipulation, evaluation, and management of sets of alternative solutions. The concepts of a set-based interface are demonstrated in two tools, Side Views and Parallel Pies, both designed for use in the domain of image manipulation. Side Views automatically generates sets of previews for one or more commands and their parameters, enabling side-by-side comparison of alternatives. Parallel Pies streamlines the process of forking, or the act of creating new, standalone alternatives, and provides a visualization to evaluate results. Two controlled laboratory studies and a third think-aloud study reveal that these tools lead to users more broadly exploring the solution space and developing more optimal solutions for some types of tasks. These studies also show that the ability to broadly explore can initially be overused, adversely affecting solution quality if not enough time is spent maturing a single solution instance. This enthusiastic use of exploration tools is especially notable because such features are entirely optional to developing a solution. As such, these results suggest the need to further research ways user interfaces can support individuals in rapidly generating sets of alternative solutions. To support future research in this direction, this work contributes a set of metrics for quantifying breadth and depth of exploration; backtracking; and dead-ends in the problem solving process. A visualization called a process diagram aids in communicating these concepts.Ph.D.Committee Chair: Mynatt, Elizabeth; Committee Member: Abowd, Gregory; Committee Member: Hudson, Scott; Committee Member: MacIntyre, Blair; Committee Member: Nakakoji, Kumiy

Data-driven shape analysis and processing

Data-driven methods serve an increasingly important role in discovering geometric, structural, and semantic relationships between shapes. In contrast to traditional approaches that process shapes in isolation of each other, data-driven methods aggregate information from 3D model collections to improve the analysis, modeling and editing of shapes. Through reviewing the literature, we provide an overview of the main concepts and components of these methods, as well as discuss their application to classification, segmentation, matching, reconstruction, modeling and exploration, as well as scene analysis and synthesis. We conclude our report with ideas that can inspire future research in data-driven shape analysis and processing

Doctor of Philosophy

dissertationVisualization has emerged as an effective means to quickly obtain insight from raw data. While simple computer programs can generate simple visualizations, and while there has been constant progress in sophisticated algorithms and techniques for generating insightful pictorial descriptions of complex data, the process of building visualizations remains a major bottleneck in data exploration. In this thesis, we present the main design and implementation aspects of VisTrails, a system designed around the idea of transparently capturing the exploration process that leads to a particular visualization. In particular, VisTrails explores the idea of provenance management in visualization systems: keeping extensive metadata about how the visualizations were created and how they relate to one another. This thesis presents the provenance data model in VisTrails, which can be easily adopted by existing visualization systems and libraries. This lightweight model entirely captures the exploration process of the user, and it can be seen as an electronic analogue of the scientific notebook. The provenance metadata collected during the creation of pipelines can be reused to suggest similar content in related visualizations and guide semi-automated changes. This thesis presents the idea of building visualizations by analogy in a system that allows users to change many visualizations at once, without requiring them to interact with the visualization specifications. It then proposes techniques to help users construct pipelines by consensus, automatically suggesting completions based on a database of previously created pipelines. By presenting these predictions in a carefully designed interface, users can create visualizations and other data products more efficiently because they can augment their normal work patterns with the suggested completions. VisTrails leverages the workflow specifications to identify and avoid redundant operations. This optimization is especially useful while exploring multiple visualizations. When variations of the same pipeline need to be executed, substantial speedups can be obtained by caching the results of overlapping subsequences of the pipelines. We present the design decisions behind the execution engine, and how it easily supports the execution of arbitrary third-party modules. These specifications also facilitate the reproduction of previous results. We will present a description of an infrastructure that makes the workflows a complete description of the computational processes, including information necessary to identify and install necessary system libraries. In an environment where effective visualization and data analysis tasks combine many different software packages, this infrastructure can mean the difference between being able to replicate published results and getting lost in a sea of software dependencies and missing libraries. The thesis concludes with a discussion of the system architecture, design decisions and learned lessons in VisTrails. This discussion is meant to clarify the issues present in creating a system based around a provenance tracking engine, and should help implementors decide how to best incorporate these notions into their own systems

A Methodology for Using Assistive Sketch Recognition For Improving a Person’s Ability to Draw

When asked to draw, most people are hesitant because they believe themselves unable to draw well. A human instructor can teach students how to draw by encouraging them to practice established drawing techniques and by providing personal and directed feedback to foster their artistic intuition and perception. This thesis describes the first methodology for a computer application to mimic a human instructor by providing direction and feedback to assist a student in drawing a human face from a photograph. Nine design principles were discovered and developed for providing such instruction, presenting reference media, giving corrective feedback, and receiving actions from the student. Face recognition is used to model the human face in a photograph so that sketch recognition can map a drawing to the model and evaluate it. New sketch recognition techniques and algorithms were created in order to perform sketch understanding on such subjective content. After two iterations of development and user studies for this methodology, the result is a computer application that can guide a person toward producing his/her own sketch of a human model in a reference photograph with step-bystep instruction and computer generated feedback

Estudo de modos de comando em cenários de interacção gestual

Tese de mestrado, Engenharia Informática (Sistemas de Informação), Universidade de Lisboa, Faculdade de Ciências, 2010Recentemente, tem-se assistido a uma “revolução tecnológica” na concepção de dispositivos computacionais que visam a interacção pessoa-máquina. Os periféricos de entrada deixaram de ser a única forma de transmitir intenções às máquinas, sendo agora possível fazê-lo com o próprio corpo. Dispositivos que permitem interacção por toque estão-se a disseminar por locais públicos, mas não é só nestes locais que o fenómeno se verifica. A quantidade de produtos comerciais que permitem este género de interacção também não pára de aumentar, pelo que é necessário compreender as vantagens e desvantagens da interacção gestual e torná-la cada vez mais eficaz. Existem muitas tecnologias que possibilitam a construção de dispositivos tácteis, variando nas suas capacidades e custos. O estudo dessas tecnologias, no decorrer deste trabalho, resultou na construção de uma mesa interactiva multi-toque de “baixo custo”. Nos dispositivos vocacionados para interacção gestual as dimensões da superfície com a qual é possível interagir são iguais às dimensões do ecrã, o que leva à necessidade de ter uma especial atenção na concepção de aplicações para estes dispositivos. As características de uma interface concebida para um ecrã de grandes dimensões poderão não ser adequadas para um ecrã de dimensões mais reduzidas, e vice-versa. Além das dimensões, o género de aplicação também influencia o paradigma de interacção. No caso específico de interacção gestual em aplicações de desenho existe a dificuldade acrescida da aplicação compreender quando o gesto do utilizador tem por objectivo desenhar ou executar um comando. Neste trabalho são apresentados dois conjuntos de gestos de comando com o objectivo de eliminar a ambiguidade existente entre os gestos em aplicações de desenho. São também apresentadas as conclusões de estudos conduzidos para atestar a qualidade dos conjuntos propostos, assim como a sua adequabilidade relativamente a diferentes dimensões de ecrã.Lately we’ve been witnessing a “technologic revolution” in the making of devices that allow human-computer interaction. Input devices are no longer the only way to instruct intentions to computers. It’s now possible to do the same using one's own body. Devices that allow touch interaction are being disseminated in public places, but it’s not only in those places that the phenomenon occurs. The number of commercial products that allow this kind of interaction doesn’t stop growing. So, it’s of vital importance to understand the advantages and disadvantages of gestural interaction and make it more effective. There are a lot of technologies that allow the construction of tactile devices, going through a wide range of capabilities and manufacturing costs. The study of those technologies, during this work, resulted in the construction of a “low-cost” multi-touch interactive table. In devices oriented for gestural interaction, the dimensions of the surface of interaction are equal to the dimensions of the screen, which demands a special attention in the design of applications for those devices. The features of an interface conceived for a large screen may not be suitable for a screen of smaller dimensions, and vice-versa. Apart from the dimensions, the kind of application can also influence the interaction paradigm. In the specific case of gestural interaction in drawing applications there’s also the increased difficulty of making the application understand when the gesture has the objective of drawing or, instead, executing a command. In this work, two sets of command gestures are introduced, with the goal of disambiguating the intent of gestures in drawing applications. Also presented are the conclusions of studies who aimed to test the quality of the proposed sets, as well as their suitability to multi-sized screens