.
An Interface for Sketching 3D Curves
Author(s): Jonathan M. Cohen, Lee Markosian, Robert C. Zeleznik, John F. Hughes, Ronen Barzel.
Proceedings: Proceedings of the 1999 ACM Symposium on Interactive 3D Graphics, pp. 17--21,
1999.
[BibTeX] 
Abstract:
The ability to specify nonplanar 3D curves is of fundamental importance in 3D modeling and animation systems. Effective techniques for specifying such curves using 2D input devices are desirable, but existing methods typically require the user to edit the curve from several viewpoints. We present a novel method for specifying 3D curves with 2D input from a single viewpoint. The user first draws the curve as it appears from the current viewpoint, and then draws its shadow on the floor plane. The system correlates the curve with its shadow to compute the curve's 3D shape. This method is more "natural" than existing methods in that it leverages skills that many artists and designers have developed from work with pencil and paper.
Art-Based Rendering of Fur, Grass, and Trees
Michael A. Kowalski, Lee Markosian, J.D. Northrup, Lubomir D. Bourdev, Ronen Barzel, Loring S. Holden, John F. Hughes.
Proceedings of Siggraph 99,
1999. [BibTeX]
Interactive Pen-and-Ink Illustration
Michael P. Salisbury, Sean E. Anderson, Ronen Barzel, David H. Salesin.
SIGGRAPH 94 Conference Proceedings, pp. 101--108, July,
1994. [BibTeX]