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Master Thesis Systems for Sketching in 3D

Author(s): Jonathan M. Cohen.
Master Thesis: Brown University, May, 2000.
[BibTeX] Find this paper on Google

In this thesis we describe two systems for sketching in 3D with a 2D input device. The first system allows the user to draw 3D stick figures. This system includes a novel technique 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. The second system, Harold, combines ideas from existing techniques and introduces new concepts to make an interactive system for creating 3D worlds. The interface paradigm in Harold is drawing: all objects are created simply by drawing them with a 2D input device. Most of the 3D objects in Harold are collections of planar strokes that are reoriented in a view-dependent way as the camera moves through the world. Virtual worlds created in Harold are rendered with a stroke-based system so that a world will maintain a hand-drawn appearance as the user navigates through it. Harold is not suitable for representing certain classes of 3D objects, especially geometrically regular or extremely asymmetric objects. However, Harold supports a large enough class of objects that a user can rapidly create expressive and visually rich 3D worlds. We conclude with a discussion of 3D sketch-based interfaces in general, and propose a framework for analyzing them. From this analysis, we propose interface design principles and a general interface design methodology. We demonstrate this methodology by designing a system for sketching motion paths in 3D.

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