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5.2 Stereoscopy

As hinted in the presentation, FORTRAN 3D offers the possibility, on certain terminals disposing of a sufficiently large number of colors, to obtain a stereoscopic set of images for a relief vision of the three-dimensional objects. The color table of these terminals must be totally modifiable (on an APOLLO station this necessitates utilization in "borrow" mode). The utilization of this function is very simple: It corresponds to call it directly after the terminal declaration (DEFDEV). Thereafter, the object is plotted totally normally without any other modification. To be able to distinguish the relief, it is of course necessary to wear a pair of glasses with red and green lenses, with the red lens on the left. If the stereoscopic image is printed on a color printer, it then necessary to look at it with red and cyan (blue and green) lenses, with red lens still on the left.

      INTEGER FUNCTION STEREO(FLAG, ECART)
      LOGICAL FLAG
      REAL ECART

generates a red-green stereoscopic couple    on a color graphics terminal, or a red-cyan stereoscopic couple on a printer.

The parameters are as follows:

• if FLAG is .TRUE., stereo
• if FLAG is .FALSE., suppress the stereo

• ECART: the pupillary distance of the observer's eyes expressed in the object's unit system (user space). It can be calculated as a function of the object's dimensions and its distance from the observer. The relief effect depends on its size. If it is too big, it can happen that the brain cannot reconstruct the image (the user will be obliged to squint too much). On return, if STEREO 0, it is because stereoscopy is not possible on the terminal in use. If not, the stereo mode is introduced.