(3) Temussi, P. A.; Lelj, F.: Tancrodi, T.: Csatiglione Moreui. M. A.; P a a m . A. Inf.J . Quan~um Chem. I9H,26,889. ( 4 ) van der Heijden, A,; Brussel, L. B. P.; Peer,H. G. Fond Chem. 1978,3,m. ( 5 ) Iwsmura. H.J . Mod. Chem. 1981.24.572,
Mazur,R. H.: Sehlatter,J.M.;Goldkamp,A.H.J.Amer. Chem.Soe. 1969.91.26e4 (7) Verlmp. A.: H w n s t r a a t e n . W.:Tipker, J.Drug Design 1976,7,165. (8) Schiffman, S. S.;C a b , H.: Lindley, M. G. Phormocol. Blocham. Behouior 1981, 15, 377. (6)
A Novel Method of Viewing Stereo Drawings D. M. Graham Vancouver Community College, Langara Campus, 100 West 49th Avenue, Vancower, BC, Canada V5Y 226 Stereo vairs of drawines are commonlv used in chemi~trv to represent three-dimensional 0hjects"such as moleculLs and surface m a ~ h sTraditionallv . thev have been viewed hv one of three methods: (1) through polarizi& screens, with the viewers using polarizing glasses; (2) using a stereo viewer into which the drawings are inserted; or (3) direct viewing of side-by-side drawings, often with the help of a card placed between the drawings and held between the eyes. Methods (1) and (2) have the disadvantage that special apparatus is required, and in method (3) the maximum size of the drawings is limited by the separation of the eyes. A method I have used successfully for some time overcomes all the above disadvantaces. and has some additional advantages of its own. ~ e s p i t e i h fact e that it is simplicity itself, I have never encountered anv reference to i t or use of it. Briefly, i t involves no more than transposing the left- and right-eye images, and viewing them with crossed eyes. Even naive viewers often achieve excellent depth perception, and viewers experienced in the parallel viewing method generally report an enhanced stereo effect. Poster-sized drawings can he prominently displayed on bulletin hoards and classroom walls, and readily examined hv several viewers simultaneouslv. Persons who have trouble crossing their eyes may he able to overcome this difficultv. even with the ~oster-sizeddrawings mentioned above, h i t h e following procedure: ~
~
1) Use a viewing distance between four and 25 times the separation
Temperaturelpre~s~rdmole fraction surface tor
Crossed viewing.
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between corresponding points on the drawings. The optimum seems to he about six to eight. Closer than four puts a severe strain on the eyes; beyond 25 it is difficult to perceive detail. 2) Hold a finger vertically at arm's length, so that its image falls between the drawings, and slowly move it closer to the eyes, which should remain focussed on it. 3) When the finger approaches the eyes so closely that focussing is difficultor uncomfortable,withdraw it vertically from the line of sight, and slowlv relax the eves while directine attention to the d;awincs. ~h&theicft-handimagtfrom fhrriphr eye meewthe right-hand irnogr from the lrft rye, the twn images shtndd t u x , grnrraring a sterro image. The drawings were hand-plotted from coordinates provided bv. a s.w e m of nrnrrams designed for use wirh a TI-59 programmable calchaior, ~ a t h - e t i l i t i e sSolid-state Software module, and PC-100C printer. The system is modular in nature, and contains 21 programs for almost every aspect of preparing stereoscopic line drawings, either from equations in any of a wide variety of coordinate systems, or from discrete data, with special emphasis on hall-stick and fusedhall molecular drawings. The system involves 7300+ lines of code recorded on 24 magnetic cards, 15 of them recorded on both sides, and can handle up to 216 coordinates simultaneously. These 216 coordinates can represent either 72 dimensionless points, or 54 points, each with a hall size associated with i t for making hall-stick or fused-hall drawings. Special routines permit drawing meridians for improved modeling of spheres, allowing for parallax distortions of shape in wide-angle views of spheres, and generating hallhall, hall-stick, and stick-stick intersection curves.
me benzene-toluene system, showing linear isotherms and curved isobars. Stereoscopic drawings placed for
Journal of Chemical Education
