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diff --git a/help/rest/stereogram.txt b/help/rest/stereogram.txt new file mode 100644 index 0000000..3f48bfa --- /dev/null +++ b/help/rest/stereogram.txt @@ -0,0 +1,109 @@ +.. _stereogram: + +.. index:: + pair: menu item; Random dot stereogram + pair: command line option; stereogram + pair: filter; Random dot stereogram + +Random dot stereogram +===================== + +Fractal images are good as a base for random dot stereograms. In case you don't +know what these are, please point your browser to Google or another search +engine and find some articles about such images, because learning to read such +images takes some effort. They make it possible to generate three dimensional +images on a normal monitor without any additional hardware, by exploiting bugs +in the human brain (although you need two working eyes, and some people never +learn to see them; they can simply ignore this feature). + +XaoS is able to generate these images in animations, so you may use all normal +XaoS functions (except palette changing and palette rotation, which makes no +sense applied to a stereogram). To make the animation yet more exciting, XaoS +emulates "falling" into the set; while you zoom in, your distance from the set +drops and drops--but you never hit it; when the set reaches the level of your +monitor, the distance is changed again so you are far away. + +To make this work right, XaoS needs to know the **exact size of your monitor**. +Because most platforms have no way to determine this, you need to use **command +line options** to tune it. If it's not set or is wrong, the stereograms will +probably be impossible to see (if your monitor is too big or resolution too +low), or the images will seem to be shallow (if your monitor is too small or +resolution too high). + +By default XaoS expects my 15" monitor (29.0cm x 21.5 cm). Another cause of +problems is the virtual screen supported by some windowed environments (like +some X servers) that makes a program think that the resolution is higher than +it actually is, and you see only part of this extra-large screen. + +The worst thing you could possibly do is to run full-screen XaoS in some +graphical windowing system (OS/2 on top of Windows or Wine on top of Linux, +perhaps) where XaoS can't tell the real size of its window at all. In such +cases, it's normally better (not to mention faster) to run XaoS natively, +rather than under such an emulation layer. + +The following command line options are provided to specify sizes: + +-screenwidth, -screenheight + + Lets you specify the size of your screen in centimeters. Note that you need + to specify the size of the visible image on the monitor, not the size with + edge borders, or the size of the tube. The simplistic 'my monitor is 17", + just turn 17" into centimeters' doesn't work; that 17" is a marketing + figure and has only a vague connection to reality. Get out a ruler and + measure it. + +-pixelwidth, -pixelheight + + Lets you specify the exact size of a single pixel, if XaoS cannot determine + this for itself from your screen size. + +These options are used by some other parts of XaoS as well, so you should use +them even when you don't want to see stereograms. You should probably write a +small starting script (or alias, or shortcut; whatever your environment uses) +that passes the correct parameters to XaoS. + +If the window is **smaller than 8cm in any direction**, you will probably be +unable to see anything; make the window bigger. The correct way to see XaoS +stereograms is: + +1 + + Start XaoS with options specifying the exact size of your screen or one + pixel on it + +2 + + Sit 60cm away from monitor + +3 + + If you use a windowed environment, resize XaoS's window to make it wider + than, say, 15 cm. + +4 + + Enable the filter (by pressing E) + +5 + + focus on a point far away from the monitor (try to use your own reflection, + if your monitor's not antireflective); the random blurring should + eventually fall into the pattern of a Mandelbrot set. + +6 + + Carefully use your mouse to zoom into interesting areas (it is easy to lose + concentration when you are not trained; but you can use the autopilot...) + +7 + + Enjoy animation :) + +If you still can't see the stereograms, it could be that the fractal, or your +eye, is deformed. A deformed fractal can be caused by your specifying your +monitor size wrongly. Visual problems that damage depth perception, as well as +problems like astigmatism, can make it impossible to see stereograms at all. + +:ref:`More information about filters <filter>` + +**Available as**: menu item, command line option |