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====================================== 3D RANDOM DOT PLOTTER, VERSION 1.0 Online Manual ====================================== DISCLAIMER What you are about to read was generated completely by me, Derry Bryson, very late at night and may contain few, if any, actual facts or useful information. No claim is made to the truthfulness or quality of the information contained. Use at your own risk! WHAT IS A RANDOM DOT STEREOGRAM? A random dot stereogram, as the name suggests, is a stereogram composed of random dots of color. In general, a stereogram consists of two images (one for each eye) designed to viewed in such a way as to create a three-dimensional (3D) image. A common example of stereograms are the discs used with the View-Master (at least they used to be common). In the case of View-Master, two pictures of each scene were taken (each shot from a slightly different position and angle) and placed on opposite sides of the disc. When viewed through the View-Master, each eye views a different image and your brain puts them together to form one apparently solid (3D) image. In a random dot stereogram both images are combined into one seemingly random field of dots. In reality, the stereogram consists of series of interleaved strips of dots. Each strip is a portion of the image for one eye. These strips alternate in the stereogram from left to right, one for the left eye, one for the right eye, one for the left eye, and so on. To view the stereogram in 3D you must focus your eyes behind the stereogram at the distance at which the strips overlap, your mind then magically perceives a pattern in the dots and combines the two images to form a solid 3D scene. There are other techniques, which I don't yet understand, that appear to be variations on random dot stereograms but don't seem quite as random. If you have any information on how these are generated, please let me know so I can incorporate them into the program as well. WHAT THE 3D RANDOM DOT PLOTTER DOES The 3D Random Dot Plotter (RD3D) takes a standard 256 color PCX graphics file (or a RAW file, described below) and generates a random dot stereogram from it that can be viewed on the computer screen or dumped out on a printer. The PCX file is not used as an image in its normal form, but rather the color of each pixel in the image indicates the depth at the given X and Y position in the scene to be depicted. Color 0 is the depth farthest from the viewer and color 255 the nearest. These files can be created with any program that can generate 256 color PCX files. The actual color of each pixel (as seen on the screen) is unimportant, only the value (depth) of the color. USING THE PROGRAM Use of the program is pretty straight forward; you will be prompted for the file to be plotted, how to plot the image, and where to display it (screen or printer). Each prompt is described in the order in which it will be encountered below: File to plot: You may type in the name of the specific name of a PCX (or RAW) file to be plotted or you may enter a wildcard pattern and the program will allow you to select from a list of files matching the pattern. For example you might enter *.PCX to select from all PCX files. NOTE: If you select a PCX format file, the file will be converted into RAW format and placed in a temporary file called TEMP.RAW which is removed when you exit the program. You will see a window appear indicating the progress of the conversion. It may take a little time depending on the size of the PCX file, but it will not be converted again as long as you are viewing the same PCX file. You should not name any RAW file you might create or obtain TEMP.RAW as it will be overwritten. Pattern width (0-8000): This is the width of the strips used to create the stereogram, as described above. The pattern width determines both the distance behind the image your eyes will have to focus to and the maximum depth in the image (the maximum depth cannot exceed the pattern width). The program will enter a hopefully useful value if you enter a 0 for the pattern width. In general, a value from 1/5 to 1/8 the width of the image width works well; however, this may end up being either too narrow or too wide for your eyes to easily focus on (especially on printed stereograms). Experimentation is what this program is good at, so try different values until you find one that works for a given image. Maximum elevation (0-8000): This is the maximum number of depth levels in the stereogram and it cannot exceed the pattern width. Lower values (between 10 and 50) seem to work best as most people can't seem to see the different depth levels anyway. Values close to the pattern width usually cause a smearing effect across the image that can be very distracting and cause problems when viewing. Maximum colors (2-256): This the the number of colors that will be used when generating the image. Color doesn't seem to add much much to the effect, but it looks pretty. Random number gen seed: This is the seed value for the random number generater. Because computers cannot really generate random numbers, but rather generate a seemingly random series of numbers we can set the starting point in this "random" series. Hence we generate the same "random" dot pattern over and over by using the same seed, or use a different seed to generate a different "random" pattern. This can be very useful because one "random" pattern may work well with a given stereogram, while another may not. If the image appears muddled, you may try different values for this field. Setting this to 0 will cause the program to load the seed from the computer's clock which should give a fairly random starting point. Once the values above are entered, you will be presented with a menu allowing selection of the device on which to display the image. Use the cursor keys to move up and down the menu items and press ENTER to select a device. Once a device is selected, another menu will appear allowing you to select the resolution to use. If you select a printer as the output device (registered version only), you will be presented with a menu allowing you to select either LPT1 or LPT2. Select the correct printer port for the selected printer. Next, select either portrait or landscape mode. Once you have selected a device for display, the image will be plotted. If viewing on the computer screen, once the image is complete the computer will beep. Press any key to erase the image and continue with another plot. If printing the image, you may press ESC to abort any time while plotting or printing. WARNING: printing a large image can take a few minutes and consume quite a bit of disk space. VIEWING A RANDOM DOT STEREOGRAM The general idea is to stare at the stereogram and force your eyes to focus behind the stereogram until the image appears. When doing this, double images will appear until your brain locks in on the image. You might want to practice doing this with your eyes a bit to get a feel for how to control your eyes in this way. The stereograms produced by this program each have two boxes along the top of the image. These are placed in the center of the image exactly pattern width apart (or the width of the strips in the stereogram apart). These can be used to help focus your eyes at the correct distance. What you want to do is adjust your focus until you see three boxes (the center dot will be two boxes overlapping). When you can see three boxes, concentrate on holding the image of the three boxes steady. Once this is pretty stable shift your view down to the rest of the image, concentrating on keeping it in focus. If the boxes are too far apart or too close together you will have a difficult time bringing the image into focus. Try to select pattern width values which position the boxes about 2 inches apart. You might want to practice shifting focus from your normal focus (two boxes) to the point where you see three boxes until you can do it without much thought. Many people find it easier to relax their eyes as one might do when day dreaming or thinking intensly about something to shift their focus. It may be difficult at first (and really difficult if you make the pattern width too wide or too narrow), but once you learn to do it you won't need the alignment boxes anymore. In fact, you will be able to view other things as stereograms. Computer keyboards are good subjects for viewing, just shift your focus in the same way as for the stereogram until the double image of the keys overlaps. Does it look more 3D when viewed as stereogram? EXAMPLE PCX FILES Several example PCX files are included for you to view. They are listed below with example viewing parameters. CONES.PCX (800 x 600) Pattern width -> 0 (let program make it up) Maximum elevation -> 0 (let program make it up) Maximum colors -> 256 Random number gen seed -> 0 Select SVGA256 and 800x600 resolution. TREX.PCX (320x200) Pattern width -> 40 Maximum elevation -> 40 Maximum colors -> 256 Random number gen seed -> 0 Select SVGA256 and 320x200 resolution CREATING YOUR OWN STEREOGRAMS Because the program can use standard 256 color PCX files, you can create your own stereograms with almost any paint program or any program that can generate 256 color PCX files. Make sure that you save the files in 256 color format, the program cannot handle monochrome or 16 color format files. Start with simple shapes like rectangles and circles of different colors. Then move on to more complex shapes. The dinosaur example PCX file (TREX.PCX) was generated by scanning an image from a coloring book into the computer in black and white and then coloring the image in a paint program to create the different depth levels. (We actually faxed the picture with a standard fax machine to a FAX/MODEM). For those with programming skills, you might try generating RAW format files (see below) from mathematical formulas. *** TECHNICAL INFORMATION *** RAW FILE FORMAT The RAW file format is specific to this program (although its pretty simple so others may inadvertantly be using it as well) and is used to store a depth map from which to generate a stereogram. This file format is used for two reasons: 1) in many PCX files, the encoding continues beyond the end of a single line making it difficult to read on a line by line basis, and 2) PCX files are more difficult to generate. This format should be selected if you decide to write a program to generate a depth map for display by this program. A RAW file consists of a short header which contains the width, length, maximum elevation, and data size for the depth map. Following the header is width * length * data size bytes which make up the depth map. In C notation, the header is defined as follows: struct { int Width, Length, DataSize, MaxElevation; } At this time the DataSize must be either 1 or 2, indicating either a 1 or 2 byte integer. While a data size of 2 should theoretically work, it has not been tested because depth values beyond 256 don't seem useful (in fact depth values above 50 really don't either). MaxElevation SHOULD be set to the maximum value of the depth data as it is used when scaling the depth values when plotting. PROGRAM DETAILS This program is written entirely in C and compiled with the Borland C++ V3.1 compiler. All plotting to the screen and printers is acomplished through the use of BGI drivers. The BGI printer drivers were obtained from Ryle Design, P.O. Box 22, Mt. Pleasant, MI, 48804, (517) 773-0587. The BGI graphics drivers for the 16 and 256 color SVGA modes are from Jordan Hargrave, 1615 Burnley Road, Charlotte, NC, 28210, (704) 553-2332. Just how did I get BGI to load 7 user drivers? Hack, hack, hack... BIBLIOGRAPY _Random Dot Stereograms_ by Andrew A. Kinsman. Copyright 1992 by Andrew Kinsman. Published by Kinsman Physics, P.O. Box 22682, Rochester, NY, 14692-2682 ($17pp). ISBN 0-9630142-1-8 Copyright (c) 1994 by Derry Bryson. All Rights Reserved. No part of this document may be reproduced in any form without specific written permission of the author.