Stereograph for linux, an advanced stereogram generator, v0.30a (c) 2000 by Fabian Januszewski ------------------------------------------------------------------------------ Stereograph comes with ABSOLUTELY NO WARRANTY; This is free software under the GPL, and you are welcome to redistribute it under certain conditions; TABLE OF CONTENTS 1.0 HOW TO INSTALL THIS PACKAGE 2.0 WHAT DOES STEREOGRAPH 2.1 WHY ADVANCED? 3.0 RENDERER BASICS 4.0 REDNERING OPTIONS 5.0 TRANSPARENCY 6.0 SINGLE IMAGE STEREOGRAMS BASICS For a VERY short summary of useful arguments ask the executable. 1.0 HOW TO INSTALL THIS PACKAGE See INSTALL for a short reference. Since release 0.17 libpng is required. There should be no problems if this library is installed under /usr/lib. Otherwise please take a look to the Makefile and modify it to suit your system. The current version of Stereograph is available at stereograph.sourceforge.net. 2.0 WHAT DOES STEREOGRAPH Stereograph is a stereogram generator. In detail it is a single image stereogram (SIS) generator. That's a program that produces twodimensional images that seem to be threedimensional (surely you know the famous works of "The Magic Eye", Stereograph produces the same output). You do _not_ need any pair of colored spectacles to regard them - everyone can learn it. 2.1 WHY ADVANCED? Yes, that's an interesting question. I know that there are thousands of SIS generators available out there. I bought one because I wanted to create something special - but I was disappointed when I created my first well-prepared composition. The quality was anything but useful. In the third dimension (the depth of the image) I was able to see different rough steps instead of really smooth transitions as expected. I couldn't believe that. I had purchased a professional program that should complete a serious job for me. So I took a pencil, a piece of paper and some time to find an optimized way of processing stereograms. Stereograph is the result of all my inventions related to this this problem. I implemented anti-aliasing for more realistic level transitions and to follow exaclty the height structure that is described in the base image. I added a zoom feature which has the same effect but is more or less not useful for stereograms on a computer screen but interesting for printing. Additionally I expanded the depth detail level of 256 levels to 765. If it should be one day necessary to increase this level again, there are no limits to extend this range up to 24 bits (16.7 millions) or even more. I was pointed to tiff which supports floating point precision; I am working on this issue. 3.0 RENDERER BASICS -b [base file] First of all we begin with a file describing the "relief" of our 3d model. The base file should contain all information about our object(s). It is a simple graphic where the brightness of a pixel defines its individual depth. The darker a pixel is, the more far away it will seem to be in the final stereogram - the brighter it is, the closer it will be. Usually only gray scale images are used to keep this information. As there are only 256 tones I decided to terminate this limitation. Of course, any gray scale image will be enough for a nice stereogram and can be used with stereograph. But if you wanna go for real quality (I mean that quality that is needed when you want to render a realistic tree and put an ant on it) you can use the full bandwidth of 765 levels by using a special color map for rendering (POVRAY does a good job - www.povray.org). Internally the RGB values of each pixel are added to calculate the depth. -t [texture file] everybody identifies with a stereogram the beautiful textures that are used to produce themselves. A good texture for a good stereogram needs a lot of love and details and some know-how or enough intuitive feelings to create one. The texture is that what everyone sees when regarding your stereogram - even if he cannot get in the third dimensions of your composition. Without an attractive texture you won't invite attractive visitors for your personal art work. ;) Technical note: the width of the texture stands for the maximum depth of any steregram and it cannot be greater than the distance of your two eyes - otherwise you won't be able to see anything in your stereogram but your beautiful great texture. As a hand rule, 100 should work nice for stereograms of 640*480 up to 800*600 pixels. Use 110 to 120 for greater ones. Hey, the random texture generator is implemented now! See below near '-w' -o [output file] The file where the stereogram is written to. If it exists stereograph won't ask you to allow it to overwrite it, it will simply do it. The following file suffices are recognized by Stereograph: tga, png, ppm; output to stdout if no output file is specified stereograph writes the graphics data to stdout. -f [output format: tga/png/ppm] This optional argument let's you choose the output format Stereograph should write. Possible values are: "tga" for 24 bit uncompressed TARGA ouput, "png" for 32 bit compressed PNG output and finally "ppm" for PPM output; otherwise Stereograph will try to select the output format by the suffix of the output file name if there is one. 4.0 REDNERING OPTIONS Quality controling arguments -a <1 to 32> anti-aliasing describes a value between 1 and 32 that declares how many pixels shall be calculated by the renderer virtually for ONE pixel. So 1 is the absolute minimum, 4 is predefined. You can calculate easily: physically you habe n depth levels, where n is the width of the texture used for the stereogram. With the AA feature you now have theoretically a*n levels. This feature increases _massively_ the color depth of the output file - so always try to keep it in true color modes (24 bits or more). I've already converted different stereograms processed with AA (7+) to indexed ones and couldn't really feel a loss of 3d quality. It's always your decision and your former free disk space or net resources, a compromise with quality. -z <1 to 32> zoom based on the same idea as AA and has the same effects but physically increases the file size. Here 1 the minimum is predefined. It increases the width AND the height of the output stereogram by z - so be very careful with your free resources, it could end up in a great colorful mess... btw, for AA and zoom only integer values are expected. perspective -d distance describes the distance of your eyes and the virtual glass that is between you and your stereogram. Default value is 5.0 since release 0.30a, feel free to walk backwards up to 20.0 steps. 1.0 distance points reflect the distance between the screen and the maximum depth. -p front factor defines the depth of the nearest point (typically mere white). This value should be rendered linear which means that for a doubled value depth contrast of the scene should be doubled too. -e <-1.0..1.0> eye shift controls the perspective along the x axis (left to right). That is if e is positive the image is shifted slightly to the right. The predefined value of 0.0 is exactly the centered perspective. layout -x <0..(base image width) - (texture width) - 1> texture instert x where the texture is inserted the first time and where the rendering process begins its rounds. standard: 0 (left image border); -y <0..texture height - 1> texture instert y y offset of the texture. standard: 0 (top); -w <1(theoretically)..texture width/base width - 1> this argument specifies the texture width to use for the stereogram. This option tells stereograph to generate a random texture or if a texture was defined it resizes the texture to match your dimension. This can be very useful when rendering transparent stereograms with a lot of different textures that all differ in their width. Note that this can only reduce the width and stereograph doesn't care about image ratios. It just cuts your texture. Random textures cannot be used with transparent rendering. -M, -G, -C, S use one of there flags to define which color type the random texture should conform to. Use -M for monochrome, -G for a grayscale or -C for a random color texture. Please note that the random texture feature cannot be combined with transparent rendering and that anti-aliasing increases the color depth of you image - even if you use a monochrome texture. To disable anti-aliasing use '-a 1'. The -S flag is experimental - it generates an artistic random texture. aid -A this flag will add a pair of black triangles at the top of the stereogram to make it easier for unexperienced eyes to achieve the magic view. base options -I inverts a base (non-transparent rendering only); -l [level adjust type: none/back/top] adjusts the base levels for transparent rendering; the keyword 'none' keeps the defined height levels of the base images; the keyword 'back' adjusts the bottom area of all upper layers to the level defined by the preceding layer; the keyword 'top' adjusts the areas of upper layers that are not as far as the preceeding layer to the level of the preceding layer; disable linear rendering algorithm -L this option disables linear rendering the anti-artefacts feature -R this feature is enabled via the -r flag and tells stereograph to process every second line in reversed order to prevent artefacts. This flag should be used only with random textures. I am working on a more stealth algorithm that could be used with any texture. Please inform me about your experiences with this feature! Your feedback is important in the further development of this idea because as I know this implementation is really unique. output types -v orders stereograph to tell you everything he's doing; 5.0 TRANSPARENCY Transparent stereograms are rendered in the same way as normal stereograms. Stereograph accepts the same parametres, so the only difference for you is to define more than one input base file and provide respectively the same number of textures. The different bases must have the same dimensions, the textures must equal themselves in the width. Otherwise stereograph will complain and even not initialize the renderer. Since release 0.29a transparent rendering needn't to be enabled via the -T flag. Example command line: > stereograph [ADDITIONAL OPTIONS] -b glass0.png glass1.png glass2.png\ -t tex0.png tex1.png tex2.png -o glass_demo.png or, running on a sh compatible shell you may simply use > stereograph [ADDITIONAL OPTIONS] -b $(ls glass?.png) -t $(ls tex?.png)\ -o glass_demo.png At the moment there's no modifier for manipulating the alhpa channels. The alphas that may be defined in your png or targa files are ignored. This feature is ALPHA. Please inform me about your experiences! 6.0 SINGLE IMAGE STEREOGRAMS BASICS First of all, some basic rules. As you can see any stereogram is composed of a texture that is repeated n times on a horizontal line but not very regularly. There is a simple rule: the more complex the scene, the more complex the resulting stereogram appears and the more difficulty it becomes for a human being to regard it in its three dimensions. The greater the contrast in the scene, the more artefacts are produced as by-product of the rendering process and the fact that not every pair of pixels on the screen is unequivocal for our eyes. Before we discuss the necessary design properties of the three dimensional scene you should know, that the texture design is at least as important as the design of the scene. The more details a texture offers the more details from your scene the final stereogram can offer to the spectator. Finally the nicer your texture the more attractive your artwork becomes for the people out there. There are a lot of ways to produce a useful scene. For your first steps you can simply use a graphics program like the GIMP for example. You will learn how to use the different depth values as effective as possible. Put some text in your scene to test the ability of detail reproduction of your texture. Not every text and every font is readable in a stereogram but feel free to play with it! Use small differences in your scene and try to avoid huge contrasts on the horizontal line. In vertical direction you can do what you want - this behavior won't result in any artifacts that may attack your beautiful stereogram. Artifacts result of symmetric pixel distance constellations that result of typical height structures of a scene in combination with a typical texture constellation. Some shifting of the texture along x or y, some changes in the texture or some adjustments of the eye perspective or of the distance could correct this. If nothing helps, alter the width of your texture by one or two pixels, that should be enough.