# Stereo

Two examples shown below are easily viewed without the add of special glasses. Stereographic visual tools can obviously add new dimensions to your data but is not always justified. Some excellent examples of applications where data can benefit from stereo are: 1. 3-D animation of chaos, 2. volume visualization of CT scans, and 3. synthesis of complex chemical structures by simulation-visualization (see Molecular Simulation Inc. software).

Stereo example shown below taken from reference: Computer Graphics, F.S. Hill, Jr., Macmillan Publishing Company, New York, 1990.

• One way to practice is to hold the index fingers of each hand upright in front of you about 2 inches apart, and to stare "through them" at a blank wall in the distance. Each eye sees two fingers, of course, but two of the fingers seem to overlap in the middle. This overlap is precisely what is desired when looking at stereo figures: Each eye sees two figures, but the middle ones are brought into perfect overlap. When the middle ones fuse together like this, the brain constructs out of them a single 3D image. Some people find it helpful to place a piece of white cardboard between the two figures and to rest their nose on it. The cardboard barrier prevents each eye from seeing the image intended for the othere eye.

• As shown above, a three-dimensional view of a parametric curve being swept out can be useful in visualizing how the simultaneous undulation of the two functions x(t) and y(t) work together to produce the curve. The figure shows a stereo view of the ellipse being swept out as t increases. An extra axis, the t-axis, is shown emanating from the x, y-plane. The shape x(t)=A cos(2 pi t) + a is plotted versus t in the x, t-plane, and the shape y(t)=B sin(2 pi t) + b is shown in the y, t-plane. The offsets a and b have been included to move the ellipse away from the origin in order to clarify the picture. As t increases, both x(t) and y(t) undulate and togther with t they sweep out a helix given by (x(t),y(t),t). The two-dimensional ellipse that is being genereated is shown on the x, y-plane.

Now try to view the helix without the projections in the x-t and y-t planes in the figures shown below.

Click image to return to Visualization home page.

R.D. Kriz
Va. Tech
College of Engineering
Revised 02/11/95

http://www.sv.vt.edu/classes/ESM4714/Gen_Prin/stereo/stereo.html