The HoloSketch VR Sketching System (Deering 1996)

Summary:
The paper discusses a general 3D drawing program called HoloSketch which allows interaction using a specialized 3D input device. The display for the HoloSketch system is a 20" CRT monitor with a resolution of 960x680, relatively high compared to head mounted displays of that time. A pair of head-tracked shutter goggles allows the user to view a sequential stereo images as one 3D image, similar to a hologram. Although the HoloSketch system was optimized for the stereo CRT display, it could be used with other types of displays in a variety of applications.
The primary input device is a 3D wand that has six degrees of freedom. The menu system for HoloSketch takes advantage of the 3D positioning of the wand and is described as "fade-up", since the geometry fades away and the menu options fade into place just in front of where the geometry was located. Commands such as movement, rotation, and finer motion control require the wand input be combined with key presses to be interpreted. Elemental animation objects can be applied to primitives to achieve animation of position, orientation, scale, and color.
The paper mentions the possibility of interoperability with geometry from other 3D programs, but does not mention what specific packages or file formats are supported. The paper demonstrates that a general purpose drawing program can be extended into 3D, but suggests that the input devices required for 3D manipulation may not be accurate enough for mainstream users.

Discussion:
The extent to which accuracy was pursued in the project is commendable. I was impressed by the fact that the system corrects for changes in intraocular distance due to the rotation of the viewer's eyes in their sockets.
The design of the interface could be improved in two ways:
1. While an RGB cube is a uniquely 3D choice for color selection, I think the colors not on the exterior of the cube would be difficult to select for a novice user that doesn't have the intuition of the RGB colorspace. In particular, to get shades of gray colors, the user would have to move along the diagonal of the cube between the vertices corresponding to black and white. Looking at the exterior of the RGB color cube would not reveal any gray colors.
2. When selecting an object, the object flashes between it's intrinsic color and white. This visual cue does not work well for colors that are very near white and is imperceptible if the object is pure white. Instead, I think an improvement would flashing between the intrinsic color and its compliment. That way, a user will be able to notice the flashing regardless of its intrinsic color.
The ability to draw two-handed was added into the program because of the test user's request. The mouse motion was mapped to control the radius of the toothpaste primitive. Instead of requiring the mouse motion to control thickness, a possible extension would be to add a second wand-like input so that the interaction could take place more directly in 3D space. Using the mouse to vary the radius requires seeing the output to get feedback on the changes, whereas a second position-tracking device would provide one-to-one control.