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Monster Media 1994 #2
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1994-06-14
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3DV
Copyright 1994
By Terran Melconian
1.0 Stereoscopic Images
1.1 How Stereoscopic Images Work
1.2 How To See Stereoscopic Images
2.0 This Program
2.1 Hardware Requirements
2.2 How To Run This Program
2.3 The Data File
1.0 STEREOSCOPIC IMAGES
Stereoscopic images make things appear in three dimensions, even though
they are only two-dimensional. Stereoscopic images are becoming popular
with still photographs and stereoscopic T.V. is being developed.
1.1 How Stereoscopic Images Work
When you look, each of your eyes sees a slightly different image,
because it is not quite in the same place as the other one. To test this,
look through one eye then the other, switching back and forth. Close things
will seem to move from side to side, but far away things will seem to stay
in the same place. Your brain puts these two images together and you seem
to see only one image in which some things seem near and some things seem far.
The things that moved from side to side the most when you looked through
your eyes in sequence are the ones that appeared the closest when you looked
through your eyes together.
To create a stereoscopic image, a person uses two cameras side by side (or
a special camera with two lenses). He then takes two pictures, one taken
from a position slightly to the right of the other. When he looks at these
pictures, he places the one that was taken by the right-hand camera on the
right, and the one taken by the left-hand camera on the left. His right eye
sees the picture taken by the right-hand camera, and his left eye sees the
picture taken by the left-hand camera. He is therefore seeing exactly the
same thing he would see if he was standing where his cameras had been when
he took the pictures. This program display a left-hand image and a right-hand
image that look similar but not identical. Your right eye sees one thing
and you left eye sees another, so the image displayed appears to be
three-dimensional.
1.2 How to See Stereo Images
If you just look at the images the way you usually look at a computer
screen, both eyes will see both images, and it will look like two
two-dimensional pictures. You need to relax your eyes so that the two
images split into four. When you relax your eyes more, the center two will
combine to become one, making a total of three. Look at the center image
and ignore the other two.
Before you try to look at the screen, put your finger a few inches away
from your nose and look at a distant wall. You should see two images of the
finger that are somewhat transparent. Now put another finger parallel to
the first one, a few inches to the side. You should see four fingers. Move
one of the fingers in or out, as needed, until two of the "ghost fingers"
join and become one solid one. You should now see one solid finger and two
transparent ones. This is the effect you need to achieve to play the game,
and you need to do it without the benefit of a wall behind the images. When
you can get these two lines to merge (that is, make three images with one of
them solid), you're ready to play. In the game, where the two images are
slightly different, the center image (the solid one) will look
three-dimensional.
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If you're having trouble, there are a few things you can do that might
help. Try placing a piece of stiff paper or cardboard between the two
lines. One edge should touch the screen (or paper, if you printed this out)
and the other edge should touch your nose. You can also print this out (if
you haven't) and hold the paper so that the two lines are at the top. Then
hold the paper so that behind it there is something far away. Try to look
at the wall and see if the lines merge.
If you still can't do it, keep trying. Sometimes it takes days to get
it. There are special viewers that help you see stereoscopic images, but
unfortunately I had no way of including one with my program. If you can't
seem to get it any other way, and you really want to be able to see it,
consider purchasing a viewer (they often come with cards of stereoscopic
images). You can find them in places like your Science Musuem Gift Shop.
It is also possible to reverse the images so that you can look at them
cross-eyed. My programs do not support this because it is tiring and
painful, and no one would want to look for long that way. If you want it,
though, mail me and I'll include it in a future version.
2.0 THIS PROGRAM
This program, 3DV, will take information which you have entered in a
data file and convert it to a stereoscopic display. Stereoscopic images are
usually quite difficult to make. One method is to use a CADD program and
take two different views, one from a viewpoint slightly to the left of the
other. While producing reasonably high quality results, this method is
time-consuming and is not practical as an introduction to stereoscopic
images. This program is designed to introduce the user to the world of
stereoscopic images and to allow the user to create simple images.
This program is distributed as Freeware (it is copyrighted but you can
distribute it freely and not feel guilty). The display routines for 3DV are
written in C. Anyone wishing to incorporate stereoscopic graphics into
his own program can contact me to purchase the routines for a small fee.
When you run the program (described below), you will see two images.
You should view them as described in sections 1.x. That's all there is to
it. Future versions of the program will allow you to rotate the images and
zoom in/out, but this version simply allows you to look at them.
If there is a demand, future releases of this program will contain the
capacity to generate a red/blue image to be used with red/blue 3D glasses.
While this picture is generally inferior to the one produced by relaxing
your eyes, almost anyone can put on some glasses while about 1/3 of all
people never master the technique required to view the two separate images.
2.1 Hardware Requirements
This display requires a VGA monitor and appropriate supporting
hardware.
2.2 How To Run This Program
The command line for the program is quite simple:
3DV [3dv datafile]
The datafile is not optional -- without it the program will not do anything.
2.3 The Data File
There are three different commands you can give in the data file. The
first is "c" for color. This sets the drawing color to be used until
another color command is encountered. The next command is "p" for point.
This command must be followed by three numbers -- the X, Y, and Z
coordinates of the point to display. X and Y coordinates range from 0 to
200 while Z coordinates range from 0 to 400. The 0 coordinate for
everything is in the lower-left front corner:
Y
Z (into screen)
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|------------------------------- X
A Z coordinate of 400 is right at the vanishing point, so a maximum of 200
or 300 is recommended. The third option acceptable in the command file is
"l" for line. The line command requires six numbers, three for the first
point and three for the second point. Future versions will also include "r"
for a filled rectangle. In addition to these commands, any line beginning
with a semicolon will be treated as a comment and ignored. Beginning a line
with anything but these four symbols will result in an error. The sample
data file, 3dv.dat, give a simply idea of how data files work.