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| author | Travis CI <zmoelnig@travis-ci.umlaeute.mur.at> | 2015-03-14 20:32:26 +0000 |
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| committer | Travis CI <zmoelnig@travis-ci.umlaeute.mur.at> | 2015-03-14 20:32:26 +0000 |
| commit | c6030846f5c1e34048774d60ca4c15e804bee839 (patch) | |
| tree | fb75f89275a78ea383c0fd64e8fe5b3ae57cc898 /Gem/manual/GemFaq.html | |
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+<html>
+<head>
+ <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
+ <meta name="Author" content="Mark Danks">
+ <meta name="GENERATOR" content="Mozilla/4.5 [en] (WinNT; I) [Netscape]">
+ <title>Gem FAQ</title>
+</head>
+<body>
+
+<center>
+<h2>
+<u>GEM FAQ</u></h2></center>
+
+<p><br>* : new question
+<br>+ : changed question
+<p><img SRC="tribar.gif" height=13 width=561>
+<h2>
+<u>QUESTIONS</u></h2>
+<i><a href="#General">GENERAL</a></i>
+<br><a href="#1.1">1.1) What is GEM?</a>
+<br><a href="#1.2">1.2) What is Pd?</a>
+<br><a href="#1.3">1.3) What platforms do GEM and Pd run on?</a>
+<br><a href="#1.4.0">1.4.0) How do I install GEM and Pd on IRIX?</a>
+<br><a href="#1.4.1">1.4.1) How do I install GEM and Pd on linux?</a>
+<br><a href="#1.4.2">1.4.2) How do I install GEM and Pd on WinNT?</a>
+<br><a href="#1.7">1.7) What is a good intro to OpenGL?</a>
+<br><a href="#1.8">1.8) Are there any web sites for Pd or GEM?</a>
+<br><a href="#1.9">1.9) What libraries does GEM use? (aka: Who does Mark
+want to thank?)</a>
+<br><a href="#1.10">1.10) Are there any restrictions on GEM?</a>
+<br><a href="#1.11">1.11) How do I use GEM in a performance?</a>
+<p><i><a href="#UsingGem">USING GEM</a></i>
+<br><a href="#2.1">2.1) How do I (???)</a>
+<br><a href="#2.2">2.2) How do I make GEM run?</a>
+<br><a href="#2.3">2.3) Why doesn't GEM run?</a>
+<br><a href="#2.4">2.4) I've got it running. Now what?</a>
+<br><a href="#2.5">2.5) On IRIX 5.3, why does GEM dump with an rld error?</a>
+<br><a href="#2.6">2.6) Why can't I compile GEM on IRIX 5.3?</a>
+<br><a href="#2.7">2.7) Why is GEM slow in general?</a>
+<br><a href="#2.8">2.8) Why is GEM slow on IRIX?</a>
+<br><a href="#2.9">2.9) Why is GEM slow on WinNT/Win95?</a>
+<br><a href="#2.10">2.10) Why is GEM slow on Linux?</a>
+<br><a href="#2.11">2.11) If I resize the window, everything looks strange.</a>
+<br><a href="#2.12">2.12) Can GEM run on a 3Dfx Voodoo card?</a>
+<br><a href="#2.13">2.13) Will GEM support hardware transform and lighting
+(T&L) ?</a>
+<br><a href="#2.14">2.14) I get an error "GEM needs Truecolor visual support".</a>
+<p><i><a href="#ViewingObjects">VIEWING OBJECTS</a></i>
+<br><a href="#3.1">3.1) Why does everything seem dim?</a>
+<br><a href="#3.2">3.2) Why does everything seem dark?</a>
+<p><i><a href="#TextureMapping">TEXTURE MAPPING</a></i>
+<br><a href="#4.1">4.1) My image doesn't appear. What is going on?</a>
+<br><a href="#4.2">4.2) My image looks strange. What is going on?</a>
+<br><a href="#4.3">4.3) Why does GEM say that it can't handle a gray image?</a>
+<br><a href="#4.4">4.4) What image formats can GEM handle?</a>
+<br><a href="#4.5">4.5) What movie formats can GEM handle?</a>
+<br><a href="#4.6">4.6) Why is pix_draw so slow?</a>
+<p><i><a href="#WorkingWithPd">WORKING WITH PD</a></i>
+<br><a href="#5.1">5.1) Why do I get clicks in the audio?</a>
+<br><a href="#5.2">5.2) How do I get audio data to GEM?</a>
+<br><a href="#5.3">5.3) Why can't GEM find an image/model file?</a>
+<br><a href="#5.4">5.4) How can I optimize my patches?</a>
+<p><i><a href="#NewGemObjects">WRITING NEW GEM OBJECTS</a></i>
+<br><a href="#6.1">6.1) How do I write a new GEM object?</a>
+<br><a href="#6.2">6.2) What are the default OpenGL states?</a>
+<p><i><a href="#ObjectSpecific">OBJECT SPECIFIC</a></i>
+<br><a href="#7.1">7.1) Why doesn't <object> exist on <platform>?</a>
+<br><a href="#7.2">7.2) Why doesn't gemtablet work?</a>
+<br><a href="#7.3">7.3) I don't want GEM to take over my tablet.
+How do I stop it?</a>
+<br><a href="#7.4">7.4) Why doesn't gemmouse work in IRIX/Linux?</a>
+<br><a href="#7.5">7.5) Why doesn't gemorb work?</a>
+<br><a href="#7.6">7.6) What is wrong with pix_video in WinNT?</a>
+<p><img SRC="tribar.gif" height=13 width=561>
+<h2>
+<u>ANSWERS</u></h2>
+<a NAME="General"></a><h3>GENERAL</h3>
+<br><a NAME="1.1"></a>1.1) What is GEM?
+<p>GEM is the Graphics Environment for Multimedia.
+It was originally written by <a href="mailto:mark@danks.org">Mark Danks</a> to generate real-time computer
+graphics, especially for audio-visual compositions. It originally ran under
+FTS/Max (which is why you might see some papers reference it), but all
+new development is under Pd.
+<p>You can get GEM at <a href="http://www.iem.at/GEM">http://gem.iem.at/</a>
+<p>GEM was sponsored by a grant from Intel (<a href="http://www.intel.com">http://www.intel.com</a>)
+<p>GEM was ported to <a href="http://www.linux.org">linux</a> by <a href="mailto:geiger@xdv.org">Günter Geiger</a>
+<p>GEM is now maintained by <a href="mailto:zmoelnig@iem.at">IOhannes m zmölnig</a>.
+<p>the core-development team consists of<ul>
+<li>chris clepper</li>
+<li>günter geiger</li>
+<li>daniel heckenberg</li>
+<li>james tittle</li>
+<li>IOhannes m zmölnig</li></ul>
+lots of contributions are made by various people (thanks to all of them)
+<p>----
+<br><a NAME="1.2"></a>1.2) What is Pd?
+<p>Pd is a real-time environment for audio and MIDI.
+It was written by <a href="mailto:msp@ucsd.edu">Miller Puckette</a>, who created FTS/Max when
+he was at IRCAM. Basically, Pd can be seen as the next generation
+of real-time visual programming languages. GEM runs inside of the
+Pd environment.
+<p>You can get Pd at <a href="http://www.crca.ucsd.edu/~msp/software.html">http://www.crca.ucsd.edu/~msp/software.html</a>
+<p>Pd is sponsored by a grant from Intel (<a href="http://www.intel.com">http://www.intel.com</a>)
+<p>----
+<br><a NAME="1.3"></a>1.3) What platforms do GEM and Pd run on?
+<p>GEM and Pd run on Windows (95, 98, ME, NT 4.0, 2000, XP), linux and macOS-X (>10.2).
+SGI-Irix (> 6.2) used to be supported but i don't have any prove that it still works).
+<a href="mailto:geiger@xdv.org">Günter Geiger</a>
+has done an initial port of GEM and Pd to Linux <a href="http://gige.epy.co.at/">http://gige.epy.co.at</a>).
+<p>GEM is now maintained by <a href="mailto:zmoelnig@iem.at">me</a> and
+developed by a team of several independent programmers (see <a href="1.1">section 1.1</a>)
+<p>----
+<br><a NAME="1.4"></a>1.4) How do I install GEM ?
+<p>----
+<br><a NAME="1.4.0"></a>1.4.0) How do I install GEM and Pd on IRIX?
+<p>See the readme for installing Pd.
+<p>GEM should be at
+<p>pd/gem
+<p>If you run GEM.INSTALL.sh, then all of the example files and documention
+should be put in the correct locations.
+<p>----
+<br><a NAME="1.4.1"></a>1.4.1) How do I install GEM and Pd on linux?
+<p>See the readme for installing Pd.
+<p>GEM should be at
+<p>chdir to <gem>/src/Gnu and build Gem following the instructions in the README.build
+(<tt>./configure; make</tt>)
+<p>If you then <tt>make install</tt>, then all of the example files and documention
+should be put in the correct locations.
+<p>if you are using debian, Gem should be available via apt</p>
+<p>if you are using an rpm-based distribution, check out the builds at planetCCRMA</p>
+<p>----
+<br><a NAME="1.4.2"></a>1.4.2) How do I install GEM and Pd on WinNT?
+<p>See the readme for installing Pd.
+<p>unzip GEM so that it is at
+<p>pd\gem
+<p>If you run GEM.INSTALL.bat, then all of the example files and documentation
+should be put in the correct locations.
+<p>there is also an installer for windows.
+<p>----
+<br><a NAME="1.4.3"></a>1.4.3) How do I install GEM and Pd on macOS?
+<p>See the readme for installing Pd.
+<p>there is also an installer for macOS.
+<p>----
+<br><a NAME="1.7"></a>1.7) What is a good intro to OpenGL?
+<p>The best book is the <u>OpenGL Programming Manual</u>
+by Mason and Woo. This is also called the "Red Book". If you search
+the web, there are many sites on OpenGL. A good starting point is
+<a href="http://www.opengl.org">http://www.opengl.org</a>.
+Also, Mark Kilgard (who used to work for SGI) has a wonderful site with
+lots of links (<a href="http://reality.sgi.com/mjk">http://reality.sgi.com/mjk</a>)
+Also, Normal Lin has written another great book on <u>3D-graphics under linux</u>
+<p>----
+<br><a NAME="1.8"></a>1.8) Are there any web sites for Pd or GEM?
+<p>Except for the ones noted above, there is the Japanese
+installation page at
+<br><a href="http://www.rinc.or.jp/~kotobuki/gem/index.htm">http://www.rinc.or.jp/~kotobuki/gem/index.htm</a>
+<p>There is a Pd mailing list. Subscription info
+is on IEM's site <a href="http://www.iem.at/mailinglists/pd-list">http://www.iem.at/mailinglists/pd-list</a>
+<p>One of pd's unofficial home-pages is at <a href="http://pd.iem.at">http://pd.iem.at</a> hosted by the
+<a href="http://iem.at">Institute of Electronic Music and Acoustics, Graz, Austria</a>
+<p>Also hosted by the <a href="http://iem.at">iem</a> is the site of the pd-community
+<a href="http://www.puredata.info">http://www.puredata.info</a>
+<p>An interesting place might also be Günter Geiger's size <a href="http://gige.epy.co.at/">http://gige.epy.co.at/</a>
+<p>there are lot's of other cool pages (search the net...)
+<p>----
+<br><a NAME="1.9"></a>1.9) What libraries does GEM use?
+(aka: Who does Mark want to thank?)
+<p>All copyrights and license info can be found in
+<br> GEM.LICENSE.TERMS
+<br> Thanks to Sam Leffner for libTiff, the TIFF image
+loader.
+<br>
+sam@engr.sgi.com
+<br> <a href="ftp://ftp.sgi.com/graphics/tiff/">ftp://ftp.sgi.com/graphics/tiff/</a>
+<br> Thanks to Masayuki Matsumoto for fstimage for OpenGL,
+the SGI
+<br> image loader.
+<br>
+matumot@dst.nk-exa.co.jp
+<br> Thanks to the Independent JPEG Group for libjpeg,
+the JPEG image loader.
+<br>
+jpeg-info@uunet.uu.net
+<br> <a href="ftp://ftp.simtel.net/pub/simtelnet/msdos/graphics/">ftp://ftp.simtel.net/pub/simtelnet/msdos/graphics/</a>
+<br> Thanks to Mark Kilgard at al. (and SGI) for glut, the openGL Utility Toolkit
+<br> <a href="http://www.pobox.com/~ndr">http://www.pobox.com/~ndr</a>
+<br> Thanks to Stephane Rehel for GLTT, the OpenGL TrueType
+render.
+<br>
+rehel@worldnet.fr
+<br> <a href="http://home.worldnet.fr/~rehel/gltt/gltt.html">http://home.worldnet.fr/~rehel/gltt/gltt.html</a>
+<br> Thanks to David Turner, Robert Wilhelm, and Werner
+Lemberg for
+<br> Freetype, a TrueType font
+rendering engine.
+<br>
+turner@enst.fr
+<br>
+robert@physiol.med.tu-muenchen.de
+<br>
+a7971428@unet.univie.ac.at
+<br> <a href="http://www.physiol.med.tu-muenchen.de/~robert/freetype.html">http://www.physiol.med.tu-muenchen.de/~robert/freetype.html</a>
+<br> Thanks to the MPEG Software Simulation Group, for
+libmpeg, the
+<br>MPEG-2 Encoder/Decoder
+<br>
+mssg@mpeg.org
+<br> <a href="http://www.mpeg.org/MSSG/">http://www.mpeg.org/MSSG/</a>
+<br> Thanks to Heroine for quicktime4linux
+a quickime Decoder
+and libmpeg3, another MPEG-2 Encoder/Decoder
+<br>MPEG-2 Encoder/Decoder
+<br>
+mssg@mpeg.org
+<br> <a href="http://heroinewarrior.com/">http://heroinewarrior.com/</a>
+<br> Thanks to LCS/Telegraphics for Wintab, the Windows
+tablet library.
+<br>
+wintab@pointing.com
+<br> Thanks to David McAllister for the Particle System
+library.
+<br>
+davemc@cs.unc.edu
+<br> <a href="http://www.cs.unc.edu/~davemc/Particle/">http://www.cs.unc.edu/~davemc/Particle/</a>
+<br> Thanks to John Stone for the Space Orb library,
+libOrb
+<br>
+j.stone@acm.org
+<br> <a href="http://www.umr.edu/~johns/projects/liborb/">http://www.umr.edu/~johns/projects/liborb/</a>
+<p>----
+<br><a NAME="1.10"></a>1.10) Are there any restrictions on GEM?
+<p>GEM is under the Gnu Public License. This basically
+means that it will always be free software.Check out <a href="http://www.gnu.org">http://www.gnu.org</a>
+for more information and read the full license in GnuGPL.LICENSE in the GEM release.
+<p>----
+<br><a NAME="1.11"></a>1.11) How do I use GEM in a performance?
+<p>This is a constant problem, because there is no consistent
+way to display video on any platform. Also, you usually do not want
+to send the entire screen, but only the GEM window. It is also useful
+to be able to edit/control the Pd patch window while the patch is actually
+running.
+<p>On SGIs, the best way is to get a video out option.
+On the SGI O2, Impact, and Onyx (Mark has used all of these), there is a
+simple connector or breakout box to do video.
+If you run the video out program, then you will get a rectangle on your screen
+which shows what is being sent out the video connector.
+Make your GEM window a little larger than 640x480 and center it in the rectangle.
+You can now project this with a standard video projector.
+<p>On PCs it is a bit harder.
+Several modern video-cards have the possibility to output several screens
+(either 2 (or more) VGA-screens or 1 VGA-screen and 1 TV (Composite or S-HVS)
+or a combination with DFTs)
+If you have a Canopus Voodoo2 card it has a video and s-video output on it. As described
+in <a href="#2.12">question 2.12</a>, you can get a Voodoo to work with
+GEM. If any one else has a better solution, please let me know.
+The nVidia Riva TNTs require that you output the full screen, so this is
+not a very good option. You can use a video scan convertor.
+Some of them only display a part of the scene, which is exactly what you
+want.
+<p>With modern multi-headed cards it is more simple:
+Configure your card to display the desktop spread over your multiple screens
+(e.g.: from left-to-right).
+On windows and macOS you can do this via the display-properties dialog.
+On linux you will have to edit your /etc/X11/XF86Config-4 file either by hand or
+(if your system supports it) via an appropriate editor (yes, nowadays there are some).
+Now create your gem-window on the second screen:
+it should have the same dimensions as the 2nd screen (e.g: "[dimen 800 600(").
+to place it at the second screen use the offset (e.g: if your primary sreen
+(the one you want for patch-editing) has the dimension 1024x768 use "[offset 1024 0(",
+which will create the gem-window 1024 pixels right of the upper-left corner
+of the total screen (and 0 pixels below it),
+which is exactly the upper-left corner of the 2nd screen.
+You most probably want to turn off the borders with "[border 0(".<br>
+<em>Note:</em> some grafix-card have openGL-hardware-acceleration only on the 1st screen
+(so you should create the gem-window on the 1st screen and move
+your patches to the 2nd screen)
+<p>If you are using an XServer for displaying (under linux) you can also use another
+computer for rendering.
+You can specify the place where the gem-window should be created with something like
+"create <<em>render.host</em>>:0.0"
+
+<p>If you are doing audio with graphics, the only solution
+to prevent clicking (<a href="#5.1">question 5.1</a>) is to run 2 computers
+and have them communicate with netsend/netreceive. We are working
+on making Pd/GEM multi-processor friendly, so if you have a multi-processor
+system, you can run everything on one machine eventually.
+<p>
+<hr WIDTH="100%"><a NAME="UsingGem"></a><h3><i>USING GEM</i></h3>
+<br><a NAME="2.1"></a>2.1)How do I (???)
+<p>Many of the general usage questions are probably
+answered in the manual or release notes. The pd mailing list is also
+a good place to find answers as well.
+<p><a NAME="2.2"></a>2.2) How do I make GEM run?
+<p>GEM is not an executable. It requires Pd to
+work and is loaded in at run time. For example, I have an alias on
+the SGI which does
+<p>/usr/people/mdanks/pd/bin/pd -lib /usr/people/mdanks/pd/gem/Gem
+<p>and on WinNT
+<p>\pdDir\pd\bin\pd -lib /pdDir/pd/gem/Gem
+<p>on UNIX-systems you will probably want to use a <tt>.pdrc</tt> file,
+ where you can put the command-line arguments for pd that you "always" need.
+<p>If you don't see a startup message from GEM, then something went wrong.
+<p>Most people use use the command shell to start Pd.
+It is not very difficult to configure Pd to run from double-clicking on the icon.
+<p>----
+<br><a NAME="2.3"></a>2.3) Why doesn't GEM run?
+<p><b>Notice that the -lib flag always requires Unix
+styles slashes</b>. This is the case even on Windows.
+<p>You may also want to use the -nosound flag.
+For instance, my PC has problems using audio (it leaks memory), so I just
+turn off the audio part of Pd. However, other people can't get GEM
+to work if the -nosound is used (on Win95). You can also try the
+-dac or -adc flags (for digital-analog-conversion only and analog-digital-conversion
+only).
+<p>----
+<br><a NAME="2.4"></a>2.4) I've got it running. Now what?
+<p>Try out the manual. It will step you through
+the basics.
+<br> You will also want to look at the example files.
+Assuming that everything is installed correctly, you can get to the examples
+by going to the Help menu in Pd and selecting examples. A bunch of
+the patches should start with gem<something>. The best one is
+<i>gem/01.basic/01.redSquare.pd</i>
+It puts a red square up on the screen and allows you to rotate it. <i>gemImage.pd</i>
+shows how to load in a TIFF file. <i>gem/03.lighting/04.moveSpheres.pd</i>
+moves two spheres around the screen. Try the other ones.
+<br> Most of the GEM objects have test patches which
+give some information about the various controls for the object.
+<p>----
+<br><a NAME="2.5"></a>2.5) On IRIX 5.3, why does GEM dump with an rld error?
+<p>GEM only works under IRIX 6.2+. The rld error
+is probably something about not having glBindTextureEXT (or something).
+OpenGL 1.0 has some extensions to speed up texture mapping (which are an
+integral part of OpenGL 1.1). However, these don't exist on IRIX
+5.3. If you recompile GEM (see the next question), things should
+work fine.
+<br> I don't have access to an IRIX machine, so don't
+expect any builds from me. Upgrading to IRIX 6.2+ is worth it.
+<p>----
+<br><a NAME="2.6"></a>2.6) Why can't I compile GEM on IRIX 5.3?
+<p>There was probably an error saying that the compiler
+couldn't find the file "dmedia/vl_vino.h" in pix_videoSGI.cpp. IRIX
+6.2+ adds new functionality to the media libraries which makes life much
+easier. You cannot compile pix_video or pix_indycam as is under 5.3.
+You can remove them from the Pix/Makefile and from the linker part of the
+global Makefile. You will also need to recompile the Td and Tiff
+libraries.
+<p>There shouldn't be any problems doing this. I haven't tried any
+of this, so if it works for someone, please let me know.
+<p>----
+<br><a NAME="2.7"></a>2.7) Why is GEM slow in general?
+<p>Examine what you are doing. If you are constantly
+changing textures, then this is probably your problem. If you have
+models with a million triangles, then this is probably the problem.
+Compare what you are doing with realistic specs on your system. Some
+systems slow down when they have to draw very large polygons (slow fill
+rate).
+<br> You can also turn on profiling to see how long it
+takes to render a frame. Send a profile message to the gemwin object.
+The number that is printed is the number of milliseconds one frame takes
+to render. 50 milliseconds is 20 frames per second. 'profile 2' is
+good if you want to see how long the image processing is taking.
+<br> profile 0 - turn off profiling
+<br> profile 1 - turn on profiling
+<br> profile 2 - turn on profiling
+and don't cache pixes
+<p>----
+<br><a NAME="2.8"></a>2.8) Why is GEM slow on IRIX?
+<p>If you are having major slowdowns, then please let
+me know. I have gotten very good performance on most machines (Indy,
+O2, Impact, Onyx2).
+<p>----
+<br><a NAME="2.9"></a>2.9) Why is GEM slow on WinNT/Win95?
+<p>You probably don't have hardware acceleration.
+You can use software rendering, but it basically useless except for extremely
+basic patches. You can get a good graphics accelerator for really
+cheap these days. I recommend a card based on nVidia's chipsets,
+such as the TNT2 or GeForce, but there are other companies such as 3dfx
+and Matrox. Make sure that you are running the latest drivers for
+your card. The basic drivers that come with the cards are usually
+very bad.
+<br> Also, PCs don't deal with lots of texture maps very
+well (they are bus limited, at least until AGP), so if you are trying to
+use lots of constantly changing texture maps
+(especially with [pix_multiimage], [pix_video] or [pix_film]), that will cause problems.
+<p>----
+<br><a NAME="2.10"></a>2.10) Why is GEM slow on Linux?
+<p>It is because you have to use Mesa, which might be
+running iin software. Mesa (<a href="http://www.mesa.org">http://www.mesa.org</a>)
+is an awesome package by Brian Paul (brianp@avid.com) which "emulates"
+OpenGL. Basically, it is a fully compliant OpenGL package, but it
+isn't officially sanctioned by the OpenGL ARB, such, it is doesn't have
+the OpenGL name. There is an acceleration package for the many graphics
+card, but I don't know anything about it.
+<br>nVidia is being very supportive of Linux:
+their TNT2 and GeForce cards work under Linux with hardware-acceleration of openGL.
+(but the drivers are proprietary)
+<br>radeon cards should also be supported very well under linux (even with open-source drivers)
+<p>----
+<br><a NAME="2.11"></a>2.11) If I resize the window, everything looks strange.
+<p>GEM doesn't trap resize events in IRIX or Linux (this
+is not a problem in WinNT). This means that OpenGL doesn't have the
+correct information to render properly. If you want to resize the
+window, send a 'dimen x y' message to gemwin before you create the window.
+<p>----
+<br><a NAME="2.12"></a>2.12) Can GEM run on a 3Dfx Voodoo card?
+<p>I (this is: Mark Danks) have a Voodoo2 card, which runs fine under WinNT.
+I use the OpenGL beta driver from 3Dfx at work all the time without any
+problems and, except that the Voodoo takes over the full screen, it seems
+to work fine. You will need to download the OpenGL Beta driver from
+3Dfx's web site at http://www.3dfx.com and put the OpenGL32.dll into the
+same directory as pd.exe (NOT gem.dll). Debugging patches is much
+easier if you have two monitors, one for the 3-D card and one for the 2-D
+card.
+<p>IMPORTANT: You MUST set the environment variable
+<p>GEM_SINGLE_CONTEXT = 1
+<p>to make the Voodoo card work. It will make a window 640x480 (which
+is the correct size for TV video out on my Canopus V2 card). On WinNT,
+right click "My Computer" and go to "Properties". On the "Environment"
+tab, you need to add the variable "GEM_SINGLE_CONTEXT" with a value of
+1.
+<br>Resizing the GEM window with a Voodoo card is not
+a great idea. The Voodoo card can only display certain window sizes and
+will clip the graphics.
+<p>For the tech heads in the audience...I create an
+OpenGL context at startup and never actually display its associated window.
+This means that GEM objects can create display lists, call OpenGL commands,
+etc. in their constructors, even if no window is actually being displayed.
+However, with the Voodoo card, there can only be one OpenGL context.
+So, instead of creating one context and just holding onto it in the background,
+I create the normal GEM window and associate the OpenGL context with it...and
+the user can never destroy or close that window.
+<p>----
+<br><a NAME="2.13"></a>2.13) Will GEM support hardware transform and lighting
+(T & L)?
+<p>Absolutely! Unlike some other APIs, OpenGL
+will automatically use hardware accelerated transform and lighting if the
+card has it. GEM gets great performance from cards like nVidia's
+GeForce.
+<p><a NAME="2.14"></a>2.14) I get an error "GEM needs Truecolor visual
+support".
+<p>This error means that your X display is running with
+paletted colors, which is the result of limited color depth. If you
+start the X display with
+<p>startx -- -bpp 16
+<p>or some higher number, then it should work fine. 32-bit color
+is the best.
+<p>
+<hr WIDTH="100%"><a NAME="ViewingObjects"></a><h3><i>VIEWING OBJECTS</i></h3>
+<br><a NAME="3.1"></a>3.1)Why does everything seem dim?<
+<p>You probably turned on lighting but don't have any
+lights in the world. Either add a light with <i>world_light</i> or
+<i>light</i>
+or turn lighting off by sending a message 'lighting 0' to the <i>gemwin</i>.
+You can also send a reset message to <i>gemwin</i> to set it back to the
+startup state (which doesn't have any lighting).
+<p>----
+<br><a NAME="3.2"></a>3.2) Why does everything seem dark?
+<p>See question 3.1.
+<br> If you are using <tt>view</tt> in your patch to change the viewpoint,
+you may not be pointing in the correct direction. You also might have translated
+everything outside of the current viewport.
+<br> Also, if you have been using single buffering ('buffer
+1' message to <i>gemwin</i>), then you might still be in that mode.
+Either send a 'buffer 2' message or a 'reset' message to <i>gemwin</i>.
+Then, destroy and create your window.
+<p>
+<hr WIDTH="100%"><a NAME="TextureMapping"></a><h3><i>TEXTURE MAPPING</i></h3>
+<br><a NAME="4.1"></a>4.1) My image doesn't appear. What is going
+on?
+<p>Normally images have to be texture-mapped onto Geos.
+You have to use [pix_texture] to map the current image onto a Geo.
+"Current" means that any pix-manipulation that is done after texturing will not be displayed.
+<p>Any Geo has a color (which is initially set to white).
+If you have set the color to black, your Geo (including the image) might be very dark.
+If you are using alpha-blending, make sure that the Geo is not invisible.
+<p>Normally images that want to be texture mapped with openGL should have dimensions that are a power of 2 in both height and width.
+Now [pix_texture] will make this totally transparent to you (so normally you don't have to care about the size of the image).
+However with non-power-of-2 images <i>pix_coordinate</i> might not behave as expected,
+because these images need absolute texture-coordinates rather than normalized ones
+(as are used with power-of-2 images): so if the texture-coordinates are set to "(0,0) (1,0) (1,1) (0,1)" you might see only the first pixel of the image (which might be black).
+<p>Also, make sure that GEM can find your image (ie,
+that the path name is correct).
+<p>----
+<br><a NAME="4.2"></a>4.2) My image looks strange. What is going
+on?
+<p>GEM supports gray8, YUV, and RGBA images. If
+it sees that the number of bits per channel and the number of channels
+is something that it should be able to handle, it tries to load the raw
+data. If you have compressed or stored the pixel data in some "strange"
+format, then GEM will probably not read the information correctly.
+<br> Also, if it is an RGBA image, then make sure that
+the alpha channel is something useful (this only matters if you are using
+the alpha channel, like in the alpha object or pix_mask).
+<p>----
+<br><a NAME="4.3"></a>4.3) Why does GEM say that it can't handle a gray
+image?
+<p>This error message occurs whenever a pix object receives
+a gray8 image and the implementor hasn't provided a way to deal with that
+format of image. (Implementors often only provide functions for GEM's <i>native</i>
+color-format RGBA. Any other color-format (like BGR) will try to call the function
+for gray8 images, which might not be supported.)
+ If you do not want to change the image format with some extern image-programm
+(like Photoshop or the Gimp) you might want to try <i>pix_rgba</a>
+or harass whoever made the object to add the functionality.
+<p>----
+<br><a NAME="4.4"></a>4.4) What image formats can GEM handle?
+<p>GEM can read in TIFF, JPEG, and SGI images.
+These can be in any color format. Gray scale images are loaded in
+as gray scale (ie, one byte per pixel). Everything else is loaded
+in or converted to an RGBA image (ie, four bytes per pixel). If there
+is an alpha channel, then it will be respected. Otherwise, the alpha
+channel will be set to fully opaque (alpha == 255).
+<p>GEM can write TIFF and JPEG images.
+TIFF-images will be full RGBA-images, wheras JPEG-files only support (compressed) RGB.
+<p>----
+<br><a NAME="4.5"></a>4.5) What movie formats can GEM handle?
+<p>The movie formats GEM can handle (still) depend on the platform
+you are using.
+<p>On Windoze you can read all AVI-files you have codecs for
+<p>On linux the readable formats depend on the libraries you had installed when you compiled GEM.
+Currently there is (optional) support for AVI, quicktime (*.MOV) and MPEG (*.MPG) files.
+Not all quicktime-formats are supported. This is unfortunate but is due to linux restrictions.
+I highly recommend that you install the mpeg3-library from Heroine because it is much more stable than mpeg1 (which comes with many linux-distributions).
+If you have compiled in support for libavifile, you will be able to open Micro$oft-AVI-files.
+If you have installed the proper codecs
+(libavifile supports a mechanism for loading codecs from windows-DLLs) you should be able to
+open almost any format.
+
+If you have serious problems, mail them <a href="mailto:zmoelnig@iem.at">to me</a>.
+(Be ready to upload the movie-file that won't work)
+<p>----
+<br><a NAME="4.6"></a>4.6) Why is <i>pix_draw</i> so slow?
+<p><i>pix_draw</i> is almost never hardware accelerated
+on PCs graphics accelerator. This means that it runs <i>extremely</i>
+slowly. Always use <i>pix_texture</i>, even if you are just displaying
+an image.
+<p>
+<hr WIDTH="100%"><a NAME="WorkingWithPd"></a><h3><i>WORKING WITH PD</i></h3>
+<br><a NAME="5.1"></a>5.1) Why do I get clicks in the audio?
+<p>If you are getting a constant stream of clicks in
+your audio, then it is probably because you are trying to do graphics and
+audio in the same process. Rendering a graphics frame usually takes
+longer than the size of the audio buffer, which is why you get clicks (the
+clicks are usually at 20Hz...the typical frame rate).
+<br> One way around this is to use two computers, one
+for graphics and one for audio. If you have enough processing power
+(or dual processors), then you can run two versions of Pd, one for graphics
+and one for audio. Just use <i>netsend</i> and <i>netreceive</i>
+to have the two versions of Pd talk to each other.
+<p>----
+<br><a NAME="5.2"></a>5.2) How do I get audio data to GEM?
+<p>One simple way to get raw audio values right now is
+to use <i>snapshot~</i>. Just set up a <i>metro</i> which bangs <i>snapshot~</i>
+and use the floating point value. If you want "musical" information,
+then use objects such as <i>env~</i>.
+You might also have a look at the <i>pix_sig2pix~</i> which interprets audio-data as pixels
+and its counterpart <i>pix_pix2sig~</i>
+<p>----
+<br><a NAME="5.3"></a>5.3) Why can't GEM find an image/model file?
+<p>This means that GEM can't locate the file.
+If you use an absolute path (with / for instance), then GEM will look there.
+Otherwise, GEM will look in the directory of where the patch is.
+Then pd/GEM will search the paths you specified at startup with the <i>-path</i> flag.
+<p>Check the following:
+<p>1) Does the file exist?
+<br> 2) Did you make a typo in the filename?
+<br> 3) Is the file in the search-path ?
+<p>----
+<br><a NAME="5.4"></a>5.4) How can I optimize my patches?
+<p>One of the biggest performance hits is having UI
+elements in your patch which have to be updated. The biggest performance
+hog is the number box. While the number box is great for debugging,
+make sure that they are all gone from your "release" patch. If you
+run a performance meter, you will see that whenever Tcl/Tk has to update
+the user interface, it sucks the entire processor. Another examples
+of this is when you move a lot of objects at once, everything jerks and
+slides across the screen. There are probably ways to improve this...
+<br> Another problem is doing unneccessary calculations.
+When you are throwing lots of numbers around, especially packing/unpacking,
+doing vector math, etc., they add up. If the calculations are going
+unused (for instance, that part of the patch is turned off), then do not
+trigger the math objects. Use <i>spigot</i> or <i>gate</i> and block
+the events early. This is especially important with objects that
+send a lot of numbers, like ~ objects or <i>line</i>/<i>tripleLine</i>.
+<p>
+<hr WIDTH="100%"><a NAME="NewGemObjects"></a><h3><i>WRITING NEW GEM OBJECTS</i></h3>
+<br><a NAME="6.1"></a>6.1) How do I write a new GEM object?
+<p>For the time being, you have to look at the code.
+It is fairly well documented and straight forward (if you know C++ and
+OOP). Start with an object which is similar to what you want and
+derive a new class. The biggest issue right now is how to load in
+GEM as a DSO/DLL. For SGIs, you will need to setenv LD_LIBRARY_PATH.
+On NT, you will need to have your path include the directory with GEM.
+<p>----
+<br><a NAME="6.2"></a>6.2) What are the default OpenGL states?
+<p>GemMan (and by association, gemwin) disables alpha
+testing, alpha blending, culling, and lighting. Lighting defaults
+to two sided, with GL_COLOR_MATERIAL enabled. The viewport is set
+to
+<p>float xDivy = (float)m_width / (float)m_height;
+<br> glMatrixMode(GL_PROJECTION);
+<br> glLoadIdentity();
+<br> glFrustum(-xDivy, xDivy, -1.0, 1.0, 1.0, 20.0);
+<br> gluLookAt(0.0, 0.0, 4.0, 0.0, 0.0, 0.0, 0.0, 1.0,
+0.0);
+<br> glMatrixMode(GL_MODELVIEW);
+<br> glViewport(0, 0, m_width, m_height);
+<p>which gives a range of about -4 to 4 in X and Y at the origin.
+This is a small range, but changing it now would break a lot of patches.
+<p>The specific functions to look at are:
+<p>GemMan::windowInit()
+<br>GemMan::resetValues()
+<br>gemhead::renderGL()
+<p>
+<hr WIDTH="100%"><a NAME="ObjectSpecific"></a><h3><i>OBJECT SPECIFIC</i></h3>
+<br><a NAME="7.1"></a>7.1) Why doesn't <object> exist on <platform>?
+<p>Usually, this is because I don't have the resources
+to get the object running on that platform. If an object that you
+want doesn't exist on your platform, then ask for it! However, if
+it is tied to hardware, then it is much less likely that I will be able
+to do anything about it (unless someone donates the hardware to me...)
+<p>----
+<br><a NAME="7.2"></a>7.2) Why doesn't <i>gemtablet</i> work?
+<p><i>gemtablet</i> only works on WinNT. I don't
+have drivers for IRIX or Linux (also, see question 7.4)
+<br> If GEM can find the tablet, then it will print a
+message at window creation time. If you don't see a message, then
+GEM doesn't think that you have a tablet.
+<br> The tablet is mapped to the size of the GEM graphics
+window.
+<p>---
+<br><a NAME="7.3"></a>7.3) I don't want GEM to take over my tablet.
+How do I stop it?
+<p>Set the environment variable
+<p>GEM_NO_TABLET = 1
+<p>----
+<br><a NAME="7.4"></a>7.4) Why doesn't <i>gemmouse</i> work in IRIX?
+<p>Basically, I don't have physical access to an SGI machine.
+This makes it hard to do some of the OS specific work.
+It should be straightforward to do the event handling, so if someone gets
+it working, I would love to include it (and give you credit). All
+you have to do is call the correct event functions from GemEvent.h and
+everything should just start to work (ie, gemmouse doesn't have any OS
+specific code in it).
+<p>----
+<br><a NAME="7.5"></a>7.5) Why doesn't gemorb work?
+<p>You need to make sure that your SpaceOrb is hooked
+up correctly. I am using a library which isn't supported by SpaceTec so
+there can be problems, although I have not had any.
+<br> <RANT> When will companies wake up and actually
+provide drivers and support for their products under WinNT? </RANT>
+<p>----
+<br><a NAME="7.6"></a>7.6) What is wrong with <i>pix_video</i> in WinNT?
+<p>I haven't completely figured out how to get access
+to the video stream in WinNT. I'm using Video for Windows with a
+Connectix QuickCam, as well as an Intel Video Capture Card, and it seems
+to assume that you are only writing to a file or previewing into a window.
+Windows tries to take over the system and doesn't really provide any stable
+hooks (unlike IRIX). If anyone knows how to deal with this, please
+let me know.
+<p><a href="index.html">[return]</a>
+<br>
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