2D Sketches Research Articles

Sketch-based free-form shape modelling with a fast and stable numerical engine

In this paper, we present a feature-based free-form shape modelling technique based on solving a fundamental problem of reconstructing the depth information from 2D sketch planes. First, to mathematically define the problem with the human perception, the proposed technique (1) formulates the 2D shaded regions on sketches by a hybrid thin plate surface model that can exhibit controlled continuity over the recovered 3D surface and (2) formulates the 1D salient open free-form curves and salient corners as linear sketch constraints. The 3D free-form shape from sketch planes is then achieved by solving a linearly constrained quadratic optimization problem which unifies both 2D region-based and 1D contour-based shape information over 2D sketches. Secondly, to solve the formulated optimization problem with an interactive-rate performance, a fast and stable numerical engine is proposed with a rigorous proof that for our specially formulated problem, system decomposition with reduced computational cost is always possible. Stability, accuracy and efficiency are studied in depth for the proposed numerical engine. Finally a prototype system utilizing the proposed technique is presented with two applications that demonstrate the usefulness and effectiveness of the proposed technique.

Using solid diagrams for tangible interface prototyping

In most design disciplines, early concept development involves paper-and-pencil brainstorming. However, we've found that when designing a tangible user interface, it's best to start with a solid diagram - a 3D sketch created using simple construction materials. In the early stages of research and concept development, solid diagrams are more suitable for rapid reconfiguration and exploration than pencil sketches. They also let us analyze modes of correspondence between physical structures and abstract-information structures. Furthermore, because we can manipulate these diagrams, they help us explore usability properties and certain design trade-offs.

A freehand sketching interface for progressive construction of 3D objects

This paper presents an intuitive, freehand sketching application for Computer Aided Design (CAD) that can reconstruct a 3D object from a single, flat, freehand sketch. A pen is used to draw 2D sketches consisting of straight and curved strokes connected at vertices. The sketches are processed by a reconstruction algorithm that uses the angular distribution of the strokes and their connectivity to determine an orthogonal 3D axis system whose projection correlates with the observed stroke orientations. The axis system is used to determine a plausible depth for each vertex. This approach works well for drawings of objects whose edges predominantly conform to some overall orthogonal axis system. A second, independent optimization procedure is then used to reconstruct each curved stroke in the original sketch, assuming that the curve is planar. New strokes can be attached to the 3D object, or drawn directly onto the object's faces. An implementation of the reconstruction algorithm based on Levenberg–Marquardt optimization allows objects with over 50 strokes to be reconstructed in interactive time.

Large mesh deformation using the volumetric graph Laplacian

We present a novel technique for large deformations on 3D meshes using the volumetric graph Laplacian. We first construct a graph representing the volume inside the input mesh. The graph need not form a solid meshing of the input mesh's interior; its edges simply connect nearby points in the volume. This graph's Laplacian encodes volumetric details as the difference between each point in the graph and the average of its neighbors. Preserving these volumetric details during deformation imposes a volumetric constraint that prevents unnatural changes in volume. We also include in the graph points a short distance outside the mesh to avoid local self-intersections. Volumetric detail preservation is represented by a quadric energy function. Minimizing it preserves details in a least-squares sense, distributing error uniformly over the whole deformed mesh. It can also be combined with conventional constraints involving surface positions, details or smoothness, and efficiently minimized by solving a sparse linear system.We apply this technique in a 2D curve-based deformation system allowing novice users to create pleasing deformations with little effort. A novel application of this system is to apply nonrigid and exaggerated deformations of 2D cartoon characters to 3D meshes. We demonstrate our system's potential with several examples.

VIRTOPSY—Scientific Documentation, Reconstruction and Animation in Forensic: Individual and Real 3D Data Based Geo-Metric Approach Including Optical Body/Object Surface and Radiological CT/MRI Scanning

Until today, most of the documentation of forensic relevant medical findings is limited to traditional 2D photography, 2D conventional radiographs, sketches and verbal description. There are still some limitations of the classic documentation in forensic science especially if a 3D documentation is necessary. The goal of this paper is to demonstrate new 3D real data based geo-metric technology approaches. This paper present approaches to a 3D geo-metric documentation of injuries on the body surface and internal injuries in the living and deceased cases. Using modern imaging methods such as photogrammetry, optical surface and radiological CT/MRI scanning in combination it could be demonstrated that a real, full 3D data based individual documentation of the body surface and internal structures is possible in a non-invasive and non-destructive manner. Using the data merging/fusing and animation possibilities, it is possible to answer reconstructive questions of the dynamic development of patterned injuries (morphologic imprints) and to evaluate the possibility, that they are matchable or linkable to suspected injury-causing instruments. For the first time, to our knowledge, the method of optical and radiological 3D scanning was used to document the forensic relevant injuries of human body in combination with vehicle damages. By this complementary documentation approach, individual forensic real data based analysis and animation were possible linking body injuries to vehicle deformations or damages. These data allow conclusions to be drawn for automobile accident research, optimization of vehicle safety (pedestrian and passenger) and for further development of crash dummies. Real 3D data based documentation opens a new horizon for scientific reconstruction and animation by bringing added value and a real quality improvement in forensic science.

A New ISO 10303 (STEP) Resource for Modeling Parameterization and Constraints

ISO 10303 (STEP) is a standard for the electronic exchange of product life-cycle data. It has been continually expanded by the addition of new capabilities since its first release by ISO in 1994. Until now, the standard has not been capable of exchanging models with parameterization and constraints such as those commonly generated by modern CAD systems. This makes it difficult to modify a model for any purpose following an exchange. However, new STEP resources have been developed to rectify this situation, and the paper reports on the the first of them to reach International Standard status. It provides the capability to associate explicitly represented parameterization and constraint information with CAD models. The primary application areas are in the 2D profiles or sketches that are inherent in many CAD model constructional procedures, in the positioning and orientation of features in 3D models and in the positioning and orientation of assembly components. Other complementary new STEP resources are briefly discussed at the end of the paper.

SMARTPAPER: An Interactive and User Friendly Sketching System

Abstract This paper describes an interactive sketching system for 3D design/modeling that diverts from the conventional menu‐and‐button interfaces of CAD tools. The system, dubbed SMARTPAPER, offers a unified sketching environment that supports direct sketching as well as gestured sketching with more emphasis on the former to encourage natural sketching styles. SMARTPAPER also provides a unified 2D and 3D drawing domain by allowing the user to sketch directly on a 3D model in addition to the usual 2D sketching from scratch. A natural sketching experience is offered by supporting casual sketching consisting of wiggly, discontinuous, overlapping strokes. The system is empowered by an array of seamlessly integrated 2D and 3D features such as 2D sketch cleaning, 3D reconstruction from 2D sketch, 3D transformations, sketching on 3D, and conventional 3D CSG operations like cutting and joining. The key to the success of SMARTPAPER is efficient and robust 3D reconstruction from a single freehand 2D sketch with minimal hints. We have employed and improved Lipson's optimization method, originally designed for offline reconstruction of engineering drawings, in our interactive system by leveraging additional clues obtained by interaction during sketching. Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Interaction Techniques, Pen‐based Interaction

Interactive Design of Botanical Trees Using Freehand Sketches and Example-based Editing

We present a system for quickly and easily designing three-dimensional (3D) models of botanical trees using free-hand sketches and additional example-based editing operations. The system generates a 3D geometry from a two-dimensional (2D) sketch using the assumption that trees spread their branches so that the distances between the branches are as large as possible. The user can apply additional gesture-based editing operations such as adding, cutting, and erasing branches. Our system also supports example-based editing modes in which many branches and leaves are generated by using a manually designed tree as an example. User experience demonstrates that our interface lets novices design a variety of reasonably natural-looking trees interactively and quickly.

Let There Be Light! Knowledge-Based 3-D Sketching Design Tools

This paper presents a framework for 3D knowledge-based sketching tools for lighting design and two software prototypes built to illustrate sketch-based interaction with intelligent systems in 3-D domains. Spot supports direct sunlight simulation and visualization in a selected time period and Light Pen supports placement of electric lighting designs to light an intended area in space. In both examples, a 3-D sketching front-end is coupled with a back-end knowledge-based system. This enables a designer to pose a problem by drawing onto a 3-D model to which the knowledge-based system offers a solution – in one case by providing quantitative data analysis; in the other by modifying the 3-D model. Spot and Light Pen's specific domain of architectural lighting design exemplifies a more general class of 3-D interaction with intelligent systems.

Supporting creative design in a visual evolutionary computing environment

In product design, sketches and images are strong devices for stimulating creativity. This paper presents a novel visual evolutionary computing environment to provide support for creative design. The 2D sketches and 3D images can be generated by combination of evolutionary computing technology and visualization technology in this environment. A tree-based genetic algorithm is illustrated by a reading lamp design example, which uses genetic algorithm with binary mathematical expression tree to form 2D sketches and programming using Visual C++6.0 and ACIS to generate 3D images. It shows that the approach is able to generate some creative solutions and demonstrates the potential of computational approach in creative design.

Peak localization of sparsely sampled luminance patterns is based on interpolated 3D surface representation

Objects in the world are typically defined by contours and local features separated by extended featureless regions. Sparsely sampled profiles were therefore used to evaluate the cues involved in localizing objects defined by such separated features (as opposed to typical Vernier acuity or other line-based localization tasks). Objects, in the form of Gaussian blobs, were defined at the sample positions by luminance cues, binocular disparity cues or both together. Remarkably, the luminance information in the sampled profiles was unable to support localization for objects requiring interpolation when the perceived depth from the luminance cue was cancelled by a disparity cue. Disparity cues, on the other hand, improved localization substantially over that for luminance cues alone. These data indicate that it is only through the interpolated depth representation that the position of the sampled object can be recognized. The dominance of a depth representation in the performance of such tasks shows that the depth information is not just an overlay to the 2D sketch of the positional information, but a core process that must be completed before the position of the object can be recognized.

Feature-based 3D non-manifold freeform object construction

This paper presents a novel technique for modeling a 3D non-manifold freeform model around a 3D reference model. To represent both the design abstractions and the incomplete topological information, a new non-manifold data structure is first defined. Our data structure embodies the functional vitalities of both the boundary representation data structure and the complex-based data structure. Along with our data structure, a set of topological operators is defined to manipulate the entities in the data structure. Based on the non-manifold data structure and the topological operators, we develop a technique to construct 3D freeform objects around a reference model. Intuitive 2D sketches are adopted to specify the detailed profile of the object constructed. The construction method is feature-based – every reference model has pre-defined features, and the feature template of the constructed object is related to the features of the reference model by feature node encoding. Therefore, the surfaces derived from one reference model can be regenerated automatically on another reference model with the same features. The geometry coverage of our geometric modeling approach includes both manifold and non-manifold 3D freeform objects.

A search engine for 3D models

As the number of 3D models available on the Web grows, there is an increasing need for a search engine to help people find them. Unfortunately, traditional text-based search techniques are not always effective for 3D data. In this article, we investigate new shape-based search methods. The key challenges are to develop query methods simple enough for novice users and matching algorithms robust enough to work for arbitrary polygonal models. We present a Web-based search engine system that supports queries based on 3D sketches, 2D sketches, 3D models, and/or text keywords. For the shape-based queries, we have developed a new matching algorithm that uses spherical harmonics to compute discriminating similarity measures without requiring repair of model degeneracies or alignment of orientations. It provides 46 to 245% better performance than related shape-matching methods during precision--recall experiments, and it is fast enough to return query results from a repository of 20,000 models in under a second. The net result is a growing interactive index of 3D models available on the Web (i.e., a Google for 3D models).

Feature based 3D garment design through 2D sketches

This paper presents a new approach for intuitively modeling a three-dimensional (3D) garment around a 3D human model by two-dimensional (2D) sketches input. Our approach is feature based—every human model has pre-defined features, and the constructed garments are related to the features on human models. Firstly, a feature template for creating a customized 3D garment is defined according to the features on a human model; secondly, the profiles of the 3D garment are specified through 2D sketches; finally, a smooth mesh surface interpolating the specified profiles is constructed by a modified variational subdivision scheme. The resulting mesh surface can be cut and flattened into 2D patterns to be manufactured. Our approach provides a 3D design tool to create garment patterns directly in the 3D space through 2D strokes, which is a characteristic not available in other computer aided garment design systems. The constructed garment patterns are related to the features on a human model, so the patterns can be regenerated automatically when creating the same style of garment for other human models. Our technique can greatly improve the efficiency and the quality of pattern making in the garment industry.

Drawing for Illustration and Annotation in 3D

We present a system for sketching in 3D, which strives to preserve the degree of expression, imagination, and simplicity of use achieved by 2D drawing. Our system directly uses user-drawn strokes to infer the sketches representing the same scene from different viewpoints, rather than attempting to reconstruct a 3D model. This is achieved by interpreting strokes as indications of a local surface silhouette or contour. Strokes thus deform and disappear progressively as we move away from the original viewpoint. They may be occluded by objects indicated by other strokes, or, in contrast, be drawn above such objects. The user draws on a plane which can be positioned explicitly or relative to other objects or strokes in the sketch. Our system is interactive, since we use fast algorithms and graphics hardware for rendering. We present applications to education, design, architecture and fashion, where 3D sketches can be used alone or as an annotation of an existing 3D model.

Fill 'er up! [Graphics filling algorithms

One of the most important and useful ideas in 2D computer graphics is the fill. Simple in concept but powerful in practice, filling is so basic a technique that there's a fill tool in just about every 2D drawing system sold today. Probably one of the first important uses of fills was to color in 2D cartoon characters, but that's just the tip of the iceberg. It's hard to know who wrote the first fill routine, but it may have been Dick Shoup, who implemented a fill technique for his Superpaint system in the mid-1970s. The next big step was Alvy Ray Smith's 24-bit flood-fill algorithm, which also included tint fill. Change came fast after that point, culminating in the sophisticated filling tools we have today. In this article, I discuss some fill techniques that I've cooked up over time to solve different jobs. I focus on techniques for identifying fill pixels.

The n-Dimensional Village

The n-Dimensional Village

Real interactivity ~Internet discussion lists\

The word "interactive" is often heard in the ravings of the popular press about the Internet, yet in truth the kind of interactivity being touted usually focuses on the latest hip and hype applications-personalized stock tickers, chat rooms, spinning 3D cartoon characters and FM radios-but interactivity also has a second, older, simpler and more direct meaning that echoes back io the original purpose of the Internet-professional collaboration. So, this article presents a review of one of the most useful and yet often most overlooked tools for interactivity on the Internet today: e-mail discussion lists (also known as listservers, listservs, mailing lists or mailservers).

Acceleration of the outer iterations of the space-dependent neutron kinetics equations solution

A variant of the Chebyshev iterative procedure, called the Chebyshev Semi-Analytical (CSA) method, is developed for acceleration of outer iterations of the space-dependent neutron kinetics equations solution. A Chebyshev polynomials sequence is chosen to optimize the convergence of residual vectors to the eigenvector of the iteration matrix. When the convergence is attained, the “exact” solution is computed by adding an error vector to the obtained approximate solution. Convergence rate of the CSA method is determined by the second eigenvalue of the iteration matrix in contrast to the Chebyshev Semi-Iterative (CSI) method where it is defined by the spectral radius of the same matrix. An adaptive Chebyshev procedure is modified for estimation of the optimum iteration parameters of the CSA method. The proposed method is implemented in the 3D neutron kinetics computer code SKETCH. The numerical results of benchmark problem calculations demonstrate that the CSA method is 2–5 times faster than the CSI method for delayed critical transient calculations. The relative effectiveness of the CSA method increases with increase in time step size.

Intuitive Three-Dimensional Sketching in Digital Space: The Synthesis of the Genetic Code for Buildings/Organisms

The author views buildings and the human-made environment as synthetic organisms, living lives that execute the will of their genetic codes. The intuitive three-dimensional (3D) sketch in the digital space of the computer acts as the generator for the future shape of a building. The author describes a series of workshops in which the intuitive 3D sketch forms the descriptive basis for the genetic code of the architecture of future buildings/organisms. He believes that when the creative potential of the intuitive 3D sketch is fully exploited, architecture can be freed from its traditional constraints. It will become more fluid and complex in appearance and will reach a higher level of performance as a result.