Interpretation of overtracing freehand sketching for geometric shapes

This paper presents a novel method for interpreting overtracing freehand sketch. The overtracing strokes are interpreted as sketch content and are used to generate 2D geometric primitives. The approach consists of four stages: stroke classification, strokes grouping and fitting, 2D tidy-up with endpoint clustering and parallelism correction, and in-context interpretation. Strokes are first classified into lines and curves by a linearity test. It is followed by an innovative strokes grouping process that handles lines and curves separately. The grouped strokes are fitted with 2D geometry and further tidied-up with endpoint clustering and parallelism correction. Finally, the in-context interpretation is applied to detect incorrect stroke interpretation based on geometry constraints and to suggest a most plausible correction based on the overall sketch context. The interpretation ensures sketched strokes to be interpreted into meaningful output. The interface overcomes the limitation where only a single line drawing can be sketched out as in most existing sketching programs, meanwhile is more intuitive to the user

A dept perception aware pen-based 3D sketching system

Ankara : The Department of Computer Engineering and the Graduate School of Engineering and Science of Bilkent Univ., 2012.Thesis (Master's) -- Bilkent University, 2012.Includes bibliographical refences.This thesis proposes a method that resembles a natural pen and paper interface to create curve based 3D sketches. The system is particularly useful for representing initial 3D design ideas without much effort. Users interact with the system by the help of a pressure sensitive pen tablet, and a camera. The input strokes of the users are projected onto a drawing plane, which serves as a paper that they can place anywhere in the 3D scene. The resulting 3D sketch is visualized emphasizing depth perception by implementing several monocular depth cues, including motion parallax performed by tracking user’s head position. Our evaluation involving several naive users suggest that the system is suitable for a broad range of users to easily express their ideas in 3D. We further analyze the system with the help of an architect to demonstrate the expressive capabilities of the system that a professional can benefit.Yıldız, CansınM.S

Modeling 3D objects with free-form surfaces using 2D sketches

Ankara : The Department of Computer Engineering and the Graduate School of Engineering and Science, Bilkent University, 2011.Thesis (Master's) -- Bilkent University, 2011.Includes bibliographical refences.Using sketches for 3D modelling is a popular research area, which is expected since using 2D sketches feels natural to most of the artists. Many techniques have been proposed to enable an intuitive and competent tool for 3D object creation. In the light of the previous research in this area, we designed a system that enables creation of 3D free-form objects with details. Our system aims to enable users to easily create simple free-form objects using strokes and perturb their surfaces using sketches that provide contours of details and shading information. We provide the user with the ability to create a 3D simple object just by drawing its silhouette. We take this stroke input and create a simple 3D object. Then we allow the user to shade the parts of the 2D silhouette drawn before. We take the shading information and use shape from shading techniques to create a height map and apply the height map on the surface of the object to construct a perturbed surface for the previously created mesh. With our system, it is possible to create and modify 3D meshes easily and intuitively.Akatürk, EmreM.S

Actas do 12º Encontro Português de Computação Gráfica

Actas do 12º Encontro Portugês de Computação Gráfica, Porto, 8-10 de Outubro de 2003O Encontro Português de Computação Gráfica teve lugar nesse ano 2003, naquela que foi a sua 12ª edição, no ISEP – Instituto Superior de Engenharia do Porto, entre os 8 a 10 de Outubro. O 12º Encontro Português de Computação Gráfica (12EPCG) veio no seguimento de encontros anteriores realizados anualmente e reuniu investigadores, docentes e profissionais nacionais e estrangeiros, que realizam trabalho ou utilizam a Computação Gráfica, Realidade Virtual e Multimédia, assim como todas as suas áreas afins, no sentido de permitir a divulgação de projectos realizados ou em curso e fomentar a troca de experiências e a discussão de questões relacionadas com a Computação Gráfica em Portugal, entre as comunidades académica,industrial e a de utilizadores finais. Este é o livro de actas do 12EPCG.Fundação Ilídio PinhoFC

SketchSoup: Exploratory Ideation Using Design Sketches

International audienceA hallmark of early stage design is a number of quick-and-dirty sketches capturing design inspirations, model variations, and alternate viewpoints of a visual concept. We present SketchSoup, a workflow that allows designers to explore the design space induced by such sketches. We take an unstructured collection of drawings as input, along with a small number of user-provided correspondences as input. We register them using a multi-image matching algorithm, and present them as a 2D interpolation space. By morphing sketches in this space, our approach produces plausible visualizations of shape and viewpoint variations despite the presence of sketch distortions that would prevent standard camera calibration and 3D reconstruction. In addition, our interpolated sketches can serve as inspiration for further drawings, which feed back into the design space as additional image inputs. SketchSoup thus fills a significant gap in the early ideation stage of conceptual design by allowing designers to make better informed choices before proceeding to more expensive 3D modeling and prototyping. From a technical standpoint, we describe an end-to-end system that judiciously combines and adapts various image processing techniques to the drawing domain – where the images are dominated not by color, shading and texture, but by sketchy stroke contours

An evaluation of user experience with a sketch-based 3D modeling system

Abstract With the availability of pen-enabled digital hardware, sketch-based 3D modeling is becoming an increasingly attractive alternative to traditional methods in many design environments. To date, a variety of methodologies and implemented systems have been proposed that all seek to make sketching the primary interaction method for 3D geometric modeling. While many of these methods are promising, a general lack of end user evaluations makes it difficult to assess and improve upon these methods. Based on our ongoing work, we present the usage and a user evaluation of a sketch-based 3D modeling tool we have been developing for industrial styling design. The study investigates the usability of our techniques in the hands of non-experts by gauging (1) the speed with which users can comprehend and adopt to constituent modeling steps, and (2) how effectively users can utilize the newly learned skills to design 3D models. Our observations and users' feedback indicate that overall users could learn the investigated techniques relatively easily and put them in use immediately. However, users pointed out several usability and technical issues such as difficulty in mode selection and lack of sophisticated surface modeling tools as some of the key limitations of the current system. We believe the lessons learned from this study can be used in the development of more powerful and satisfying sketch-based modeling tools in the future.

Hybrid sketching : a new middle ground between 2- and 3-D

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 2005.Includes bibliographical references (leaves 124-133).This thesis investigates the geometric representation of ideas during the early stages of design. When a designer's ideas are still in gestation, the exploration of form is more important than its precise specification. Digital modelers facilitate such exploration, but only for forms built with discrete collections of high-level geometric primitives; we introduce techniques that operate on designers' medium of choice, 2-D sketches. Designers' explorations also shift between 2-D and 3-D, yet 3-D form must also be specified with these high-level primitives, requiring an entirely different mindset from 2-D sketching. We introduce a new approach to transform existing 2-D sketches directly into a new kind of sketch-like 3-D model. Finally, we present a novel sketching technique that removes the distinction between 2-D and 3-D altogether. This thesis makes five contributions: point-dragging and curve-drawing techniques for editing sketches; two techniques to help designers bring 2-D sketches to 3-D; and a sketching interface that dissolves the boundaries between 2-D and 3-D representation. The first two contributions of this thesis introduce smooth exploration techniques that work on sketched form composed of strokes, in 2-D or 3-D. First, we present a technique, inspired by classical painting practices, whereby the designer can explore a range of curves with a single stroke. As the user draws near an existing curve, our technique automatically and interactively replaces sections of the old curve with the new one. Second, we present a method to enable smooth exploration of sketched form by point-dragging. The user constructs a high-level "proxy" description that can be used, somewhat like a skeleton, to deform a sketch independent of(cont.) the internal stroke description. Next, we leverage the proxy deformation capability to help the designer move directly from existing 2-D sketches to 3-D models. Our reconstruction techniques generate a novel kind of 3-D model which maintains the appearance and stroke structure of the original 2-D sketch. One technique transforms a single sketch with help from annotations by the designer; the other combines two sketches. Since these interfaces are user-guided, they can operate on ambiguous sketches, relying on the designer to choose an interpretation. Finally, we present an interface to build an even sparser, more suggestive, type of 3-D model, either from existing sketches or from scratch. "Camera planes" provide a complex 3-D scaffolding on which to hang sketches, which can still be drawn as rapidly and freely as before. A sparse set of 2-D sketches placed on planes provides a novel visualization of 3-D form, with enough information present to suggest 3-D shape, but enough missing that the designer can 'read into' the form, seeing multiple possibilities. This unspecified information--this empty space--can spur the designer on to new ideas.by John Alex.Ph.D