Silhouette and Pen-and-Ink Rendering

Hand-drawn pen-and-ink drawings have fascinated me for a long time. Using non-photorealistic rendering I have worked on generating such drawings consisting of silhouette lines and other strokes with the computer.

My specific interests lie in object-space techniques because this allows easy stylization and further processing of the extracted features. I worked on silhouette as well as hatching line extraction from polygonal models and the necessary hidden line removal. I also did research to reduce the visual artifacts that sometimes occur in this type of rendering. The programs implemented within the framework of the OpenNPAR project demonstrate most of these techniques.

Other techniques address stylization issues such as how to represent style information in NPR line rendering pipelines and the interactive, object hierarchy-independent stylization of line drawings as shown in the image below:

Using G-strokes to capture style information and NPR Lenses to stylize renditions independent of their object hierarchy.

Recently, I worked on fast silhouette and stipple rendering of implicit surfaces. The project made use of some of the polygonal techniques mentioned above to speed up the process of finding silhouette lines and stipple points on the surface of an implicit shape. This is typically difficult because implicits lack the inherent sampling that polygonal shapes possess. The new technique not only allows interactive rendering but also interactive modelling at the same time which is a significant improvement over previous techniques.

Pen-and-ink rendering created from an implicit model.

Publications

• Petra Neumann, Tobias Isenberg, and Sheelagh Carpendale. NPR Lenses: Interactive Tools for Non-Photorealistic Line Drawings. In Andreas Butz, Brian Fisher, Antonio Krüger, Patrick Olivier, and Shigeru Owada, editors, Proceedings of the 7^th International Symposium on Smart Graphics (SG 2007, June 25–27, 2007, Kyoto, Japan), volume 4569 of Lecture Notes in Computer Science, pages 10–22, Berlin, Heidelberg, 2007. Springer-Verlag. (PDF, 2414698 bytes) (doi:10.1007/978-3-540-73214-3_2)
• Ryan Schmidt, Tobias Isenberg, Pauline Jepp, Karan Singh, and Brian Wyvill. Sketching, Scaffolding, and Inking: A Visual History for Interactive 3D Modeling. In Maneesh Agrawala and Oliver Deussen, editors, Proceedings of the Fifth International Symposium on Non-Photorealistic Animation and Rendering (NPAR 2007, August 4–5, 2007, San Diego, California, USA), pages 23–32, New York, 2007. ACM Press. (PDF, 9725249 bytes) (doi:10.1145/1274871.1274875)
• Tobias Isenberg and Angela Brennecke. G-Strokes: A Concept for Simplifying Line Stylization. Computers & Graphics, 30(5):754–766, October 2006. (PDF, 3584265 bytes) (doi:10.1016/j.cag.2006.07.006)
• Tobias Isenberg, Petra Neumann, Sheelagh Carpendale, Mario Costa Sousa, and Joaquim A. Jorge. Aesthetics of Hand-Drawn and Computer-Generated Illustrations. In Bruce Gooch, László Neumann, Werner Purgathofer, and Mateu Sbert Casasayas, editors, Dagstuhl Seminar 06221 on Computational Aesthetics in Graphics, Visualization and Imaging. 2006. Also see the paper at NPAR 2006.
• Tobias Isenberg, Petra Neumann, Sheelagh Carpendale, Mario Costa Sousa, and Joaquim A. Jorge. Non-Photorealistic Rendering in Context: An Observational Study. In Doug DeCarlo and Lee Markosian, editors, Proceedings of the Fourth International Symposium on Non-Photorealistic Animation and Rendering (NPAR 2006, June 5–7, 2006, Annecy, France), pages 115–126, New York, 2006. ACM Press. Also see the presentation at Dagstuhl Seminar 06221. (PDF, 37376205 bytes) (doi:10.1145/1124728.1124747)
• Petra Neumann, Tobias Isenberg, and Sheelagh Carpendale. NPR Lenses: Local Effect Control for Non-Photorealistic Line Drawings. In Doug DeCarlo and Lee Markosian, editors, Poster Presentations of the Fourth International Symposium on Non-Photorealistic Animation and Rendering (NPAR 2006, June 5–7, 2006, Annecy, France), 2006. Also see the paper at Smart Graphics 2007 and the technical report. (PDF, 658412 bytes)
• Ryan Schmidt, Tobias Isenberg, and Brian Wyvill. Interactive Pen-and-Ink Rendering for Implicit Surfaces. In Hanspeter Pfister, editor, ACM SIGGRAPH 2006 Conference Abstracts and Applications (Technical Sketch at SIGGRAPH 2006, July 30–August 3, 2006, Boston, Massachusetts, USA), New York, 2006. ACM Press. Also see the paper at NPAR 2007. (PDF, 1197926 bytes) (doi:10.1145/1179849.1179972)
• Tobias Isenberg and Angela Brennecke. G-Strokes: A Concept for Simplifying Line Stylization. Technical Report 2005-780-11, Department of Computer Science, University of Calgary, Canada, April 2005. Also see the article in Computers & Graphics. (PDF, 1909506 bytes) (doi:1880/46353)
• Tobias Isenberg, Angela Brennecke, Mario Costa Sousa, and Sheelagh Carpendale. Beyond Pixels: Illustration with Vector Graphics. Technical Report 2005-804-35, Department of Computer Science, University of Calgary, Canada, December 2005. (PDF, 6424414 bytes) (doi:1880/45776)
• Tobias Isenberg, Petra Neumann, Sheelagh Carpendale, Mario Costa Sousa, and Joaquim A. Jorge. Non-Photorealistic Rendering in Context: An Observational Study. Technical Report 2005-805-36, Department of Computer Science, University of Calgary, Canada, December 2005. Also see the paper at NPAR 2006 and the presentation at Dagstuhl Seminar 06221. (PDF, 39012237 bytes) (doi:1880/45777)
• Petra Neumann, Tobias Isenberg, M. Sheelagh T. Carpendale, and Thomas Strothotte. Expressive Distortion of Strokes and 3D Meshes. Technical Report 2005-776-07, Department of Computer Science, University of Calgary, Canada, March 2005. Also see the paper at Smart Graphics 2007 and the poster at NPAR 2006. (PDF, 2477272 bytes) (doi:1880/45771)
• Christian Tietjen, Tobias Isenberg, and Bernhard Preim. Combining Silhouettes, Shading, and Volume Rendering for Surgery Education and Planning. In Ken W. Brodlie, David J. Duke, and Kenneth I. Joy, editors, Data Visualization 2005: Proceedings of the Eurographics / IEEE VGTC Symposium on Visualization (EuroVis 2005, June 1–3, 2005, Leeds, England, UK), Eurographics Workshop Series, pages 303–310, 335, Aire-la-Ville, Switzerland, 2005. Eurographics Association. (PDF, 4500939 bytes) (doi:10.2312/VisSym/EuroVis05/303-310)
• Tobias Isenberg, Roland Jesse, Oscar Meruvia, and Thomas Strothotte. Seeing Between the Strokes. Technical Report, FIN Preprint Series 11/2004, Department of Computer Science, Otto-von-Guericke University of Magdeburg, Germany, 2004. (PDF, 7255412 bytes)
• Roland Jesse, Tobias Isenberg, Bernd Nettelbeck, and Thomas Strothotte. Dynamics by Hybrid Combination of Photorealistic and Non-Photorealistic Rendering Styles. Technical Report, FIN Preprint Series 5/2004, Department of Computer Science, University of Magdeburg, Germany, 2004. (PDF, 5659642 bytes)
• Johannes Zander, Tobias Isenberg, Stefan Schlechtweg, and Thomas Strothotte. Creating High Quality Hatching Illustrations. Technical Report, FIN Preprint Series 12/2004, Department of Computer Science, Otto-von-Guericke University of Magdeburg, Germany, 2004. Also see the paper at Eurographics 2004. (PDF, 6642264 bytes)
• Johannes Zander, Tobias Isenberg, Stefan Schlechtweg, and Thomas Strothotte. High Quality Hatching. Computer Graphics Forum (Proceedings of Eurographics 2004, August 30–September 3, 2004, Grenoble, France), 23(3):421–430, September 2004. Also see the technical report which contains additional details and examples. (PDF, 5110034 bytes) (doi:10.1111/j.1467-8659.2004.00773.x)
• Nick Halper, Tobias Isenberg, Felix Ritter, Bert Freudenberg, Oscar Meruvia, Stefan Schlechtweg, and Thomas Strothotte. OpenNPAR: A System for Developing, Programming, and Designing Non-Photorealistic Animation and Rendering. In Jon Rokne, Reinhard Klein, and Wenping Wang, editors, Proceedings of the 11^th Pacific Conference on Computer Graphics and Applications, Pacific Graphics 2003 (PG 2003, October 8–10, Canmore, Alberta, Canada), pages 424–428, Los Alamitos, CA, 2003. IEEE Computer Society, IEEE. Short paper and poster. (PDF, 2293447 bytes) (doi:10.1109/PCCGA.2003.1238288)
• Tobias Isenberg, Bert Freudenberg, Nick Halper, Stefan Schlechtweg, and Thomas Strothotte. A Developer's Guide to Silhouette Algorithms for Polygonal Models. IEEE Computer Graphics and Applications, 23(4):28–37, July/August 2003. (PDF, 1737442 bytes) (doi:10.1109/MCG.2003.1210862)
• Henry Sonnet, Tobias Isenberg, Jana Dittmann, and Thomas Strothotte. Illustration Watermarks for Vector Graphics. In Jon Rokne, Reinhard Klein, and Wenping Wang, editors, Proceedings of the 11^th Pacific Conference on Computer Graphics and Applications, Pacific Graphics 2003 (PG 2003, October 8–10, Canmore, Alberta, Canada), pages 73–82, Los Alamitos, CA, 2003. IEEE Computer Society, IEEE. (PDF, 1545648 bytes) (doi:10.1109/PCCGA.2003.1238249)
• Tobias Isenberg, Nick Halper, and Thomas Strothotte. Stylizing Silhouettes at Interactive Rates: From Silhouette Edges to Silhouette Strokes. Computer Graphics Forum (Proceedings of Eurographics 2002, September 2–6, 2002, Saarbrücken, Germany), 21(3):249–258, September 2002. (PDF, 829789 bytes) (doi:10.1111/1467-8659.00584)
• Tobias Isenberg, Maic Masuch, and Thomas Strothotte. 3D Illustrative Effects for Animating Line Drawings. In Proceedings of the IEEE International Conference on Information Visualisation (IV 2000, July 19–21, 2000, London, England, UK), pages 413–418, Los Alamitos, California, 2000. IEEE Computer Society, The Institute of Electrical and Electronics Engineers, Inc. (PDF, 1214046 bytes) (doi:10.1109/IV.2000.859790)
• Tobias Isenberg. Visualisierung von Modellierungsentscheidungen und Unsicherheiten in virtuellen Rekonstruktionen [Visualization of Modeling Decisions and Uncertainties in Virtual Reconstructions]. Unpublished report at the Department of Simulation and Graphics, Otto-von-Guericke University Magdeburg, Germany, 1999. In German, also see paper at CGI 1999. (PDF, 2587313 bytes)
• Tobias Isenberg. Visualisierungseffekte in liniengraphischen Animationen und Stillbildern [Visualization Effects in Animated and Single-Frame Line Drawings]. Diplom thesis at the department of simulation and graphics, Otto-von-Guericke University Magdeburg, Germany, 1999. In German, also see paper at IV 2000. (PDF, 6914065 bytes)
• Thomas Strothotte, Maic Masuch, and Tobias Isenberg. Visualizing Knowledge about Virtual Reconstructions of Ancient Architecture. In Proceedings Computer Graphics International 1999 (CGI 99, June 7–11, 1999, Canmore, Alberta, Canada), pages 36–43, Los Alamitos, CA, 1999. The Computer Graphics Society, IEEE Computer Society. (PDF, 1904742 bytes) (doi:10.1109/CGI.1999.777901)