SBM08: Sketch Based Interfaces and Modeling 2008

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https://diglib.eg.org/handle/10.2312/418

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Sketching Piecewise Clothoid Curves
(The Eurographics Association, 2008) McCrae, James; Singh, Karan; Christine Alvarado and Marie-Paule Cani
We 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. Further, adjacent clothoid segments can be locally blended to result in a G3 curve with curvature that predominantly varies linearly with arc length. We also handle intended sharp corners or G1 discontinuities, as independent rotations of clothoid pieces. Our formulation is ideally suited to conceptual design applications where aesthetic fairness of the sketched curve takes precedence over the precise interpolation of geometric constraints. We show the effectiveness of our results within a system for sketch-based road and robot-vehicle path design, where clothoids are already widely used.
A Data Collection Tool for Sketched Diagrams
(The Eurographics Association, 2008) Blagojevic, Rachel; Plimmer, Beryl; Grundy, John; Wang, Yong; Christine Alvarado and Marie-Paule Cani
Repositories of digital ink sketches would be invaluable for testing and evaluation of sketch recognition software. However, there is no existing tool for flexible data collection and management of digital ink data for building repositories of hand drawn diagrams. We present a tool for the efficient collection, management and analysis of ink data. A resultant dataset records each ink stroke accompanied by participant and diagram information, stroke labels and measurements of various stroke features. This tool enables the effective construction of a large database of sketches to aid the development of recognition techniques.
Rapid Sketch Modeling of Clouds
(The Eurographics Association, 2008) Wither, Jamie; Bouthors, Antoine; Cani, Marie-Paule; Christine Alvarado and Marie-Paule Cani
Clouds are an important visual element of any natural scene and computer artists often wish to create specific cloud shapes (for example in the film Amélie, as depicted in Fig 1). We describe a sketch based interface for modeling cumulous clouds. This interface allows rapid construction of a 3D cloud surface representation (mesh) using an underlying point based implicit surface representation. This mesh is rendered using the technique [BNM*08], resulting in a realtime cloud modeling and rendering system.
Matisse: Painting 2D regions for Modeling Free-Form Shapes
(The Eurographics Association, 2008) Bernhardt, Adrien; Pihuit, Adeline; Cani, Marie-Paule; Barthe, Loic; Christine Alvarado and Marie-Paule Cani
This paper presents Matisse, an interactive modeling system aimed at providing the public with a very easy way to design free-form 3D shapes. The user progressively creates a model by painting 2D regions of arbitrary topology while freely changing the view-point and zoom factor. Each region is converted into a 3D shape, using a variant of implicit modeling that fits convolution surfaces to regions with no need of any optimization step. We use intuitive, automatic ways of inferring the thickness and position in depth of each implicit primitive, enabling the user to concentrate only on shape design. When he or she paints partly on top of an existing primitive, the shapes are blended in a local region around the intersection, avoiding some of the well known unwanted blending artifacts of implicit surfaces. The locality of the blend depends on the size of smallest feature, enabling the user to enhance large, smooth primitives with smaller details without blurring the latter away. As the results show, our system enables any unprepared user to create 3D geometry in a very intuitive way.
Supporting Reinterpretation in Computer-Aided Conceptual Design
(The Eurographics Association, 2008) Jowers, Iestyn; Prats, Miquel; Lim, Sungwoo; McKay, Alison; Garner, Steve; Chase, Scott; Christine Alvarado and Marie-Paule Cani
This paper presents research that aims to inform the development of computational tools that better support design exploration and idea transformation - key objectives in conceptual design. Analyses of experimental data from two fields - product design and architecture - suggest that the interactions of designers with their sketches can be formalised according to a finite number of generalised shape rules defined within a shape grammar. Such rules can provide a basis for the generation of alternative design concepts and they have informed the development of a prototype shape synthesis system that supports dynamic reinterpretation of shapes in design activity. The notion of sub-shapes' is introduced and the significance of these to perception, recognition and the development of emergent structures is discussed. The paper concludes with some speculation on how such a system might find application in a range of design fields.
Using Sketches and Retrieval to Create LEGO Models
(The Eurographics Association, 2008) Santos, Tiago; Ferreira, Alfredo; Dias, Filipe; Fonseca, Manuel J.; Christine Alvarado and Marie-Paule Cani
In this paper we describe a system to create LEGO models using sketches. Although there are a few applications to create LEGO models, they are difficult to use, mainly due to the searching and manipulation mechanisms that they (do not) offer. Here, we propose a sketch based approach, where users can easily insert parts, by specifying their dimensions through sketches and the system suggests a list of possible parts. To help with the modeling and the manipulation we also developed a constraint based mechanism, which keeps parts connected, performs snapto- grid and detects collisions. Experimental tests with users revealed that our approach is easier and faster to use than a conventional application, such as LeoCAD.
AlgoSketch: Algorithm Sketching and Interactive Computation
(The Eurographics Association, 2008) Li, Chuanjun; Miller, Timothy S.; Zeleznik, Robert C.; Jr., Joseph J. LaViola; Christine Alvarado and Marie-Paule Cani
We present AlgoSketch, a pen-based algorithm sketching prototype with supporting interactive computation. AlgoSketch lets users fluidly enter and edit 2D handwritten mathematical expressions in the form of pseudocode-like descriptions to support the algorithm design and development process. By utilizing a novel 2D algorithmic description language and a pen-based interface, AlgoSketch users need not work with traditional, yet complex 1D programming languages in the early parts of algorithm development. In this paper, we present the details behind AlgoSketch including the design of our 2D algorithmic description language, support for iteration and flow of control constructs and a simple debugging trace tool. We also provide some examples of how AlgoSketch might be used in the context of image analysis and number-theoretic calculation problems found. Based on preliminary user feedback, we believe AlgoSketch has the potential to be used to design and test new algorithms before more efficient code is implemented. In addition, it can support users who may not be familiar with any advanced programming languages.
Sketching Faces
(The Eurographics Association, 2008) Gunnarsson, Orn; Maddock, Steve; Christine Alvarado and Marie-Paule Cani
Faces can be modelled using a number of techniques. Existing faces can be transferred to a digital form using equipment such as laser scanners. New faces can be constructed using commercial modelling tools, or using specialist software, e.g. Photo-fit software. We present a technique that can create a 3D head using intuitive 2D sketching techniques. This involves bringing together two types of graphics applications: sketching interfaces and systems used to create 3D faces, through the mediation of a statistical model.
ShortStraw: A Simple and Effective Corner Finder for Polylines
(The Eurographics Association, 2008) Wolin, Aaron; Eoff, Brian; Hammond, Tracy; Christine Alvarado and Marie-Paule Cani
In this paper we introduce ShortStraw, a simple and highly accurate polyline corner finder. ShortStraw uses a bottom-up approach to find corners by: (1) resampling the points of the stroke, (2) calculating the straw distance between the endpoints of a window around each resampled point, and (3) taking the points with the minimum straw distance to be corners. Using an all-or-nothing accuracy measure, ShortStraw achieves an accuracy more than twice that of the current best benchmark.
SOUSA: Sketch-based Online User Study Applet
(The Eurographics Association, 2008) Paulson, Brandon; Wolin, Aaron; Johnston, Joshua; Hammond, Tracy; Christine Alvarado and Marie-Paule Cani
Although existing domain-specific datasets are readily available, most sketch recognition researchers are forced to collect new data for their particular domain. Creating tools to collect and label sketched data can take time, and, if every researcher creates their own toolset, much time is wasted that could be better suited toward advanced research. Additionally, it is often the case that other researchers have performed collection studies and collected the same types of sketch data, resulting in large duplications of effort. We propose, and have built, a generalpurpose sketch collection and verification tool that allows researchers to design custom user studies through an online applet residing on our group's web page. By hosting such a tool through our site, we hope to provide researchers with a quick and easy way of collecting data. Additionally, our tool serves to create a universal repository of sketch data that can be made readily available to other sketch recognition researchers.
Sketch-Based Search and Composition of 3D Models
(The Eurographics Association, 2008) Lee, Jeehyung; Funkhouser, Thomas; Christine Alvarado and Marie-Paule Cani
There is growing interest in developing tools with which novice users can create detailed 3D models of their own designs. The most popular approaches to this problem include sketch-based interfaces and part-composition systems. The sketch-based modeling systems provide natural interfaces for creating 3D models from 2D sketches, but are generally limited to creating simple geometric models. The part-composition systems provide tools for combining parts extracted from a database of 3D models, and thus can generate very detailed 3D models, but usually with much higher overhead and expertise required by the user for manipulating 3D geometry interactively. In this paper, we introduce a new modeling method that overcomes these limitations by combining both approaches - we introduce a modeling system for parts composition with a sketching interface. The system allows the user to find a part in a database and composite it into a model with a single sketch. This approach combines the benefits of both approaches - i.e., it allows creation of highly detailed models/scenes (as details come from parts in the database), while 2D sketched strokes provide all the information for part selection and composition (no 3D manipulation is required, in general). To enable this modeling method, we investigate an algorithm for 3D shape search with 2D sketch as a shape query and a part placement algorithm which automatically orients, translates, scales, and attaches a new part into a modeling scene by taking the user sketch as a hint. User experiences with our prototype system show that novice users can create interesting and detailed models with our system.
Paper-based Scribble Simplification:Where Do We Stand?
(The Eurographics Association, 2008) Bartolo, Alexandra; Camilleri, Kenneth P.; Fabri, Simon G.; Borg, Jonathan C.; Christine Alvarado and Marie-Paule Cani
This paper presents a formal evaluation of the paper-based scribble simplification algorithm described in [BCFB07] and [BCFB08]. A comparative analysis of different aspects of the algorithm with other algorithms described in the literature such as Sparse Pixel Vectorization, spatial moving average filtering and Principal Component Analysis is performed, hence establishing the qualities of this paper-based scribble simplification algorithm. To quantify the performance of the algorithm, performance measures established in the literature, such as the Pixel Recovery Index are used when suitable. However, since there exists no quantitative measure which measures scribble simplification, this paper proposes a new methodology with which scribble simplification may be quantitatively assessed. Through the evaluation described in this paper, we will be able to determine remaining difficulties in the interpretation of paper-based scribbles and hence identify future research areas.
A Sketch-Based Method to Control Deformation in a Skeletal Implicit Surface Modeler
(The Eurographics Association, 2008) Sugihara, Masamichi; Groot, Erwin de; Wyvill, Brian; Schmidt, Ryan; Christine Alvarado and Marie-Paule Cani
Skeletal implicit surfaces offer many advantages for sketch-based modeling systems, such as blending, CSG, and a procedural object hierarchy. Free-form deformation (FFD) is also extremely useful in this context, however existing FFD approaches do not support implicit surface representations, and FFD lattice manipulation is timeconsuming compared to sketch-based techniques. In this paper, we describe an FFD technique suitable for implicit surface representations. To enhance real-time feedback, we split the problem into an approximate formulation used during interactive deformation, and a more robust variational technique which preserves desirable scalar field properties. As an interface to manipulate the deformation, we introduce a sketch-based volumetric peeling interface. The designer's task is to draw a curve on the surface, and pull or push the surface to the desirable position via the curve. Subsequently, the deformation is automatically defined. Results show that a desirable deformation can be easily achieved while preserving implicit properties.
MathBrush: A Case Study for Pen-based Interactive Mathematics
(The Eurographics Association, 2008) Labahn, George; Lank, Edward; Marzouk, Mirette; Bunt, Andrea; MacLean, Scott; Tausky, David; Christine Alvarado and Marie-Paule Cani
Current generations of computer algebra systems require users to transform two dimensional math expressions into one dimensional strings, to master complex sets of commands, and to analyze lengthy output strings for relevant information. MathBrush is a system, designed based on research in education pedagogy, that provides a pen-based interface to many of the features of computer algebra systems. We describe relevant work in education pedagogy as a motivation for MathBrush's design. We highlight aspects of MathBrush that are unique from other contemporary pen-math systems. Finally, we present the results of a thinkaloud evaluation of the MathBrush system. Together, these observations validate aspects of the current design of MathBrush, suggest areas for refinement, and inform the design of future pen-math systems.
Sketch-based Parameterization of L-systems using Illustration-inspired Construction Lines
(The Eurographics Association, 2008) Anastacio, Fabricio; Prusinkiewicz, P.; Sousa, Mario Costa; Christine Alvarado and Marie-Paule Cani
We present a sketch-based interface for parameter control of rule-based models. It allows intuitive specification and creation of plant structures with L-systems. Construction lines inspired by concept sketches are employed as a way to define and manipulate global-to-local characteristics of L-system models. The overall structure, posture and proportions of the plant are initially sketched by the user as construction line arrangements. They are automatically encoded as a set of positional functions controlling internode lengths, branching angles, organ sizes, and stem shape. These positional functions are then used to parameterize pre-defined L-system templates representing phyllotactic patterns for positioning lateral organ surfaces such as leaves and petals. Results are presented for single monopodial plant structures, all generated from simple input construction line sketches.
Investigating User Requirements and Usability of Immersive Three-dimensional Sketching for Early Conceptual Design - Results from Expert Discussions and User Studies
(The Eurographics Association, 2008) Israel, Johann Habakuk; Zöllner, Christian; Mateescu, Magda; Korkot, Rasim; Bittersmann, Gunnar; Fischer, Patrick Tobias; Neumann, Jens; Stark, Rainer; Christine Alvarado and Marie-Paule Cani
As immersive 3-d user interfaces reach broader acceptance, their use as sketching media is attracting both commercial and academic research. So far little is known about user requirements and cognitive aspects of immersive 3-d sketching. Also its integration into the workflow of virtual product development is far from being solved. In this paper we present results from two focus group expert discussions and a comparative user study on immersive 3-d sketching which we conducted among professional furniture designers. The results of the focus groups show a strong interest in using the three-dimensional space as a medium for conceptual design. Users expect it to provide new means for the sketching process, namely spatiality, one-to-one proportions, associations, and formability. Eight groups of functions required for 3-d sketching were generated during the discussions. The results from the user study show that both the sketching process and the resulting sketches differ in the 2-d and 3-d condition, namely in terms of the perceived fluency of sketch creation, of the perceived appropriateness for the task, of the perceived stimulation by the medium, movement speed, sketch sizes, details, functional aspects, and usage time. We argue that both 2-d and 3-d sketching are relevant for early conceptual design. As progress towards 3-d sketching, new tangible interactive tools are needed which account for the user's perceptual and cognitive abilities.
Sketch and Paint-based Interface for Highlight Modeling
(The Eurographics Association, 2008) Pacanowski, Romain; Granier, Xavier; Schlick, Christophe; Poulin, Pierre; Christine Alvarado and Marie-Paule Cani
In computer graphics, highlights capture much of the appearance of light reflection off a surface. They are generally limited to pre-defined models (e.g., Phong, Blinn) or to measured data. In this paper, we introduce new tools and a corresponding highlight model to provide computer graphics artists a more expressive approach to design highlights. For each defined light key-direction, the artist simply sketches and paints the main highlight features (shape, intensity, and color) on a plane oriented perpendicularly to the reflected direction. For other light-and- view configurations, our system smoothly blends the different user-defined highlights. Based on GPU cabilities, our solution allows real-time editing and feedback. We illustrate our approach with a wide range of highlights, with complex shapes and varying colors. This solution also demonstrates the simplicity of introduced tools.
Repoussé: Automatic Inflation of 2D Artwork
(The Eurographics Association, 2008) Joshi, Pushkar; Carr, Nathan A.; Christine Alvarado and Marie-Paule Cani
We describe a new system for the interactive enhancement of 2D art with 3D geometry. Repoussé creates a 3D shape by inflating the surface that interpolates the input curves. By using the mean curvature stored at boundary vertices as a degree of freedom, we are able to control the inflated surface intuitively and efficiently using a single linear system. Repoussé handles both smooth and sharp position constraints. Position constraint vertices can also have curvature constraints for controlling the inflation of the local surface. We show the applications of our system in font design, stroke design, photo enhancement and freeform 3D shape design.
Automatic Interpretation of Depiction Conventions in Sketched Diagrams
(The Eurographics Association, 2008) Lockwood, Kate; Lovett, Andrew; Forbus, Ken; Dehghani, Morteza; Usher, Jeff; Christine Alvarado and Marie-Paule Cani
Diagrams are used in many educational settings to convey physical and spatial information. Sketching is used, in turn, to test students' understanding of course concepts. The availability of Tablet PCs offer an exciting opportunity to create intelligent tutoring systems which automatically provide students with feedback on sketched work, and to create systems which can capture knowledge via interaction with people. However, for such systems to provide useful and relevant feedback, the software must be able to interpret diagrams that students have drawn. Interpreting diagrams correctly requires an understanding of some basic depiction conventions common in diagrammatic representation. Here we describe how to combine general semantic information about objects in sketched diagrams with geometric information from the sketch to aid in the interpretation of regions and edges. This system is implemented as an extension to the CogSketch sketch understanding system.
From Paper to Machine: Extracting Strokes from Images for use in Sketch Recognition
(The Eurographics Association, 2008) Rajan, Pankaj; Hammond, Tracy; Christine Alvarado and Marie-Paule Cani
Sketching is a way of conveying ideas to people of diverse backgrounds and culture without any linguistic medium. With the advent of inexpensive tablet PCs, online sketches have become more common, allowing for stroke-based sketch recognition techniques, more powerful editing techniques, and automatic simulation of recognized diagrams. Online sketches provide significantly more information than paper sketches, but they still do not provide the flexibility, naturalness, and simplicity of a simple piece of paper. Recognition methods exist for paper sketches, but they tend to be domain specific and don't benefit from the advances of stroke-based sketch recognition. Our goal is to combine the power of stroke-based sketch recognition with the flexibility and ease of use of a piece of paper. In this paper we will present a stroke-tracing algorithm that can be used to extract stroke data from the pixilated image of the sketch drawn on paper. The presented method handles overlapping strokes and also attempts to capture sequencing information, which is helpful in many sketch recognition techniques. We present preliminary results of our algorithm on several paper-drawn, hand-sketched, scanned-in pixilated images.

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