Note: Graduate Assistantships in computer graphics and visualization are currently available.
To date, most systems for information visualization have been 2D or 2.5D. Many of them provide very useful visualization tools and are good for showing two-dimensional relationships. Some can show the relationship among three parameters of the information space, but they fail to capitalize on the human perception system's ability to understand full three-dimensional volumetric space. With the correct use of volume visualization techniques and careful mapping of information to visualization attributes, the user can easily perceive more than three-dimensions of data at once.
A glyph (or icon) is a graphical object whose attributes--
location, size, shape, color, etc.--represent different dimensions of the data.
Three parameters of the data establish the location of the glyph,
while other parameters may affect its size, shape, color, opacity,
orientation, etc.
Many dimensions of the data can then be perceived at the same time.
A good example of glyphs is the simple stick-and-ball model used by chemists
in visualizing complex molecule structures.
The colored balls represent individual atoms in the molecule, and
the sticks of varying length stand for the bonds among the atoms.
Computational Fluid Dynamics (CFD) applications commonly use the
simple, but effective, arrow glyph to represent the flow vectors.
The length of the arrow indicates the magnitude, and
the head shows the direction of flow.Two-dimensional icons have been thoroughly studied and successfully applied to many areas: road signs, fighter aircraft HUDs, computer desktops, etc. The meaning of a well designed icon is immediately understood by the user without extensive learning. With 3D glyphs, the designer can encode more information with a single glyph than is possible with a 2D icon.
One advantage of the glyph approach is that its attributes are naturally associated with perceptual elements. For example, a large glyph can represent the importance of a data parameter; a bright color, such as red or yellow, can stand for urgency; and, transparency can show the apparent age of the information, as it slowly fades into time.
The human visual system is adept at seeing objects in space, making glyphs ideally suited for representing three-dimensional data. When combined with trackers and data gloves, glyphs allow two-handed direct manipulation of data in space.
Minimal immersion allows the user to interact with both hands and see and hear in stereo, while remaining in his normal working environment with its associated reference material. Additionally, the application may retain a 2D interface, allowing its use in the absence of 3D devices.
The user may wear a pair of stereoscopic glasses for three-dimensional vision and, by holding a tracker in each hand, is able to directly manipulate the data objects in space. In our minimally immersive set up, the user sits in front of a graphics console consisting of a keyboard, mouse, monitor, and a pair of 3D magnetic trackers, each of which has three buttons used to initiate various interaction tasks.
In our two-handed interaction approach, the non-dominant (left) hand sets up the frame of reference within which the dominant (right) hand performs intricate tasks. The tracker held in the left hand is responsible for low frequency context setting operations, and the other in the right hand is responsible for high frequency picking and manipulation operations. The use of two trackers gives the user access to double the spatial bandwidth, since both hands can be employed in parallel to quickly achieve the desired operation. Additionally, this approach takes advantage of a person's innate proprioceptive knowledge of where his two hands are in space. In contrast, with the spaceball and mouse approach, the user not only loses the natural use of his hands, but must also learn to operate the spaceball as a context setting device. This approach separates the user's position from the object's orientation, resulting in unnatural interaction (e.g., left and right may be reversed when the object is facing toward the user).
A typical use scenario in Telltale is to type in a text query and find the indexed documents that match the query. The documents returned by Telltale can also be used as queries. The Information Retrieval (IR) term for this is relevance feedback. Each returned document is rated by a similarity score that measures how well the document matches the query.
The Stereoscopic Field Analyzer (SFA) is a minimally-immersive volumetric visualization system, which uses glyphs to represent scalar and vector data. The user can change rendering parameters, such as glyph type, data volume size, scale factor, etc., using the Sundial 3D hierarchical menu. Pressing button 2 on the left hand tracker pops up the menu. The menu items are selected by pivoting the shadow stick about its base until the stick's endpoint lies visually in front of the desired item. Pressing button 3 grabs the data volume in the left hand, and pressing the button again releases it. Holding the volume in the left hand allows for natural rotation, zooming, and interactive exploration of the data volume.
In the SFA-Telltale system, each queried document is rendered as a 3D glyph. Several parameters of the document can be mapped to various glyph attributes, including size, color, and opacity. In our current application, the publication date of the document may be encoded as glyph color: new documents are assigned bright red, and old ones dark blue. Glyph opacity can be used as a filtering mechanism to remove documents unrelated to a theme. Additionally, two-handed spatial subsetting can be used to remove irrelevant documents.
With the Probe attached to the right hand tracker, the user can examine document details by pointing at the glyph and pressing a tracker button. SFA then displays the document ID next to the glyph and sends it back to the Telltale server for display in the hypertext viewer.
