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  Tutorial
Tutorial about T-real
by SKT

Prof.
Hyewon Seo

University of
Strasbourg
France


Prof.
Fredric Cordier

University of
Strasbourg
France








Title
Sketch-based modeling of 3D graphical objects

Abstract
Sketching is one of the most natural ways to exchange ideas. It has been shown that human beings have an inherent ability to understand sketches and are able to reconstruct 3D models from sketches instantly and effortlessly. Since the first computer animation movie, artists have used 3D modeling software to create 3D shapes, which requires hours of work even by well-trained artists. Sketch-based interfaces for 3D modeling offer an appealing alternative; creating and animating 3D shapes could become as simple as drawing with a tablet and a digital pen.

Research on sketch-based modeling began 50 years ago with the seminal Sketchpad by Ivan Sutherland. Since then, hundreds of papers have been published, exploring various aspects of sketch-based modeling and animation. The purpose of this tutorial is to explore the most important aspects of sketch-based modeling, from the preprocessing of sketch strokes to the problem of 3D reconstruction. In the introductory part, we will explain what sketch-based modeling is and why it can help artists create and animate 3D shapes. We will also explain some aspects of how humans interpret sketches. In particular, researchers have shown that we build a mental representation of sketches, using cues such as the compactness of shapes, the generic view assumption, shape simplicity and the use of symmetry. The second part of course will be dedicated to the problem of sketch preprocessing. Sketches are usually drawn by hand; as such, sketches are inherently imprecise. Different approaches will be presented for the filtering and processing of strokes. The purpose of stroke filtering is to generate a smooth curve that closely approximates the strokes provided by the artist. The processing step consists of grouping strokes, fitting them to precise geometric shapes, and interpreting these strokes as gestural input. In the third part, we will introduce the problem of sketch-based modeling of curves and surfaces. Two different classes of methods will be presented -- multi-view modeling where artists create shapes in an iterative manner using different editing tools and frequent changes of viewpoint, and single-view modeling where the 3D shape is entirely created using a single sketch provided by the artist. The last part of the course will focus on sketch-based modeling using prior-knowledge. Humans naturally make use of prior knowledge when recognizing complex objects from incomplete or ambiguous input. We will show how this class of methods is particularly adapted to the 3D reconstruction of complex shapes or animation control.


Speaker Introduction
Hyewon Seo is a CNRS researcher working at the University of Strasbourg as an associate professor since 2009. Before joining CNRS, she has been an assistant professor at the Chungnam National University in South Korea for 5 years where she led the Computer Graphics and Applications Lab. Her research interests include data-driven methods, intuitive control, and spatio-temporal analysis of graphical objects. She holds BSc & MSc degrees in CS from KAIST, and PhD in CS from University of Geneva, Switzerland. She is author of over 50 publications in internationally renowned conferences and journals such as ACM SIGGRAPH/Eurographics SCA, IEEE TVCG, CGF, and The Visual Computer. Hyewon Seo serves editorial boards of Computer Animation and Virtual World (2012~, associate editor) and The Visual Computer (associate editor-in-chef, October 2015~), and has served Computer Graphics International in 2015 as conference co-chair.

Frederic Cordier is an associate professor of Computer Science at the University of Haute-Alsace and at the University of Strasbourg. His research interests include sketch-based modeling, 3D modeling, texturing and human?computer interaction. Frederic holds a Ph.D. in Computer Science from the University of Geneva, Switzerland. He is an associated editor of Visual Computer.