We regard SKETCH as a proof-of-concept application, but it has many flaws. Many of the gestures were based on an ad hoc trial and error approach, and some of the gestures still do not satisfy us. For example, the pause in the freehand curve gesture rapidly becomes annoying in practice -- the user wants to do something, and is forced to wait. Possible solutions of course include using more modifier keys, although we would rather find a solution that preserves the simplicity of the interface.
SKETCH is based on an interface that is stretched to its limits. We expect that adding just a few more gestures will make the system hard to learn and hard to use. We'd like to perform user studies on ease of use, ease of learning, and expressive power for novice users as a function of the number of gestures. We're also interested in trying to determine to what extent artistic and spatial abilities influence users' preference for sketching over other modeling interfaces.
We have begun to implement a tablet-based version of SKETCH. The current generation of tablet pens include pressure sensitivity in addition to a single finger-controlled button, and one "eraser-like" button. In order to develop an equivalent interface for the tablet, we simply need to treat a specific pressure level as a button click to achieve the equivalent of three buttons. Therefore, the button 1 drawing interactions described for the mouse are done by simply pressing hard enough with the penpoint of the tablet pen. To achieve the button 2 operations of the mouse, the user simply presses the finger controlled button on the tablet pen. Finally, to effect camera motion, the user turns the pen over and uses its "eraser" to manipulate the camera. Our initial efforts with a tablet based interface lead us to believe that a tablet based system could be far more effective than a mouse based system, especially if pressure sensitivity is cleverly exploited.
SKETCH is a tool for initial design -- the ``doodling'' stage, where things are deliberately imprecise. But initial design work should not be cast away, and we are examining ways to export models from SKETCH to modelers that support more precise editing, so that the sketch can be moved towards a final design. Since subsequent analysis and design often requires re-thinking of some initial choices, we are also interested in the far more difficult task of re-importing refined models into SKETCH and then re-editing them, without losing the high-precision information in the models except in the newly-sketched areas.
The scenes shown here and in the video are relatively simple. Will sketching still work in a complex or cluttered environments? We do not yet have enough experience to know. Perhaps gestures to indicate an ``area of interest,'' which cause the remainder of the scene to become muted and un-touchable might help.
The tradeoffs in gesture design described in Section 4 must be further explored, especially with user-studies.
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