From 9b873693bdcbfe439a4157564ece781f67e58239 Mon Sep 17 00:00:00 2001 From: Travis CI Date: Thu, 9 May 2019 20:35:45 +0000 Subject: Gem 01b1861db023a225d01a4d5a519cf54f09f631f5 linux/amd64 built 'master:01b1861db023a225d01a4d5a519cf54f09f631f5' for linux/amd64 --- Gem/manual/GemFaq.html | 1334 ++++++++++++++++++++++++------------------------ 1 file changed, 667 insertions(+), 667 deletions(-) (limited to 'Gem/manual/GemFaq.html') diff --git a/Gem/manual/GemFaq.html b/Gem/manual/GemFaq.html index fe2e175..1fe41cd 100644 --- a/Gem/manual/GemFaq.html +++ b/Gem/manual/GemFaq.html @@ -1,667 +1,667 @@ - - - - - - - Gem FAQ - - - -
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-GEM FAQ

- -


* : new question -
+ : changed question -

-

-QUESTIONS

-GENERAL -
1.1) What is GEM? -
1.2) What is Pd? -
1.3) What platforms do GEM and Pd run on? -
1.4.0) How do I install GEM and Pd on IRIX? -
1.4.1) How do I install GEM and Pd on linux? -
1.4.2) How do I install GEM and Pd on WinNT? -
1.7) What is a good intro to OpenGL? -
1.8) Are there any web sites for Pd or GEM? -
1.9) What libraries does GEM use? (aka: Who does Mark -want to thank?) -
1.10) Are there any restrictions on GEM? -
1.11) How do I use GEM in a performance? -

USING GEM -
2.1) How do I (???) -
2.2) How do I make GEM run? -
2.3) Why doesn't GEM run? -
2.4) I've got it running. Now what? -
2.5) On IRIX 5.3, why does GEM dump with an rld error? -
2.6) Why can't I compile GEM on IRIX 5.3? -
2.7) Why is GEM slow in general? -
2.8) Why is GEM slow on IRIX? -
2.9) Why is GEM slow on WinNT/Win95? -
2.10) Why is GEM slow on Linux? -
2.11) If I resize the window, everything looks strange. -
2.12) Can GEM run on a 3Dfx Voodoo card? -
2.13) Will GEM support hardware transform and lighting -(T&L) ? -
2.14) I get an error "GEM needs Truecolor visual support". -

VIEWING OBJECTS -
3.1) Why does everything seem dim? -
3.2) Why does everything seem dark? -

TEXTURE MAPPING -
4.1) My image doesn't appear. What is going on? -
4.2) My image looks strange. What is going on? -
4.3) Why does GEM say that it can't handle a gray image? -
4.4) What image formats can GEM handle? -
4.5) What movie formats can GEM handle? -
4.6) Why is pix_draw so slow? -

WORKING WITH PD -
5.1) Why do I get clicks in the audio? -
5.2) How do I get audio data to GEM? -
5.3) Why can't GEM find an image/model file? -
5.4) How can I optimize my patches? -

WRITING NEW GEM OBJECTS -
6.1) How do I write a new GEM object? -
6.2) What are the default OpenGL states? -

OBJECT SPECIFIC -
7.1) Why doesn't <object> exist on <platform>? -
7.2) Why doesn't gemtablet work? -
7.3) I don't want GEM to take over my tablet. -How do I stop it? -
7.4) Why doesn't gemmouse work in IRIX/Linux? -
7.5) Why doesn't gemorb work? -
7.6) What is wrong with pix_video in WinNT? -

-

-ANSWERS

-

GENERAL

-
1.1) What is GEM? -

GEM is the Graphics Environment for Multimedia. -It was originally written by Mark Danks 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. -

You can get GEM at http://gem.iem.at/ -

GEM was sponsored by a grant from Intel (http://www.intel.com) -

GEM was ported to linux by Günter Geiger -

GEM is now maintained by IOhannes m zmölnig. -

the core-development team consists of

-lots of contributions are made by various people (thanks to all of them) -

---- -
1.2) What is Pd? -

Pd is a real-time environment for audio and MIDI. -It was written by Miller Puckette, 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. -

You can get Pd at http://www.crca.ucsd.edu/~msp/software.html -

Pd is sponsored by a grant from Intel (http://www.intel.com) -

---- -
1.3) What platforms do GEM and Pd run on? -

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). -Günter Geiger -has done an initial port of GEM and Pd to Linux http://gige.epy.co.at). -

GEM is now maintained by me and -developed by a team of several independent programmers (see section 1.1) -

---- -
1.4) How do I install GEM ? -

---- -
1.4.0) How do I install GEM and Pd on IRIX? -

See the readme for installing Pd. -

GEM should be at -

pd/gem -

If you run GEM.INSTALL.sh, then all of the example files and documention -should be put in the correct locations. -

---- -
1.4.1) How do I install GEM and Pd on linux? -

See the readme for installing Pd. -

GEM should be at -

chdir to <gem>/src/Gnu and build Gem following the instructions in the README.build -(./configure; make) -

If you then make install, then all of the example files and documention -should be put in the correct locations. -

if you are using debian, Gem should be available via apt

-

if you are using an rpm-based distribution, check out the builds at planetCCRMA

-

---- -
1.4.2) How do I install GEM and Pd on WinNT? -

See the readme for installing Pd. -

unzip GEM so that it is at -

pd\gem -

If you run GEM.INSTALL.bat, then all of the example files and documentation -should be put in the correct locations. -

there is also an installer for windows. -

---- -
1.4.3) How do I install GEM and Pd on macOS? -

See the readme for installing Pd. -

there is also an installer for macOS. -

---- -
1.7) What is a good intro to OpenGL? -

The best book is the OpenGL Programming Manual -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 -http://www.opengl.org. -Also, Mark Kilgard (who used to work for SGI) has a wonderful site with -lots of links (http://reality.sgi.com/mjk) -Also, Normal Lin has written another great book on 3D-graphics under linux -

---- -
1.8) Are there any web sites for Pd or GEM? -

Except for the ones noted above, there is the Japanese -installation page at -
http://www.rinc.or.jp/~kotobuki/gem/index.htm -

There is a Pd mailing list. Subscription info -is on IEM's site http://www.iem.at/mailinglists/pd-list -

One of pd's unofficial home-pages is at http://pd.iem.at hosted by the -Institute of Electronic Music and Acoustics, Graz, Austria -

Also hosted by the iem is the site of the pd-community -http://www.puredata.info -

An interesting place might also be Günter Geiger's size http://gige.epy.co.at/ -

there are lot's of other cool pages (search the net...) -

---- -
1.9) What libraries does GEM use? -(aka: Who does Mark want to thank?) -

All copyrights and license info can be found in -
GEM.LICENSE.TERMS -
Thanks to Sam Leffner for libTiff, the TIFF image -loader. -
-sam@engr.sgi.com -
ftp://ftp.sgi.com/graphics/tiff/ -
Thanks to Masayuki Matsumoto for fstimage for OpenGL, -the SGI -
image loader. -
-matumot@dst.nk-exa.co.jp -
Thanks to the Independent JPEG Group for libjpeg, -the JPEG image loader. -
-jpeg-info@uunet.uu.net -
ftp://ftp.simtel.net/pub/simtelnet/msdos/graphics/ -
Thanks to Mark Kilgard at al. (and SGI) for glut, the openGL Utility Toolkit -
http://www.pobox.com/~ndr -
Thanks to Stephane Rehel for GLTT, the OpenGL TrueType -render. -
-rehel@worldnet.fr -
http://home.worldnet.fr/~rehel/gltt/gltt.html -
Thanks to David Turner, Robert Wilhelm, and Werner -Lemberg for -
Freetype, a TrueType font -rendering engine. -
-turner@enst.fr -
-robert@physiol.med.tu-muenchen.de -
-a7971428@unet.univie.ac.at -
http://www.physiol.med.tu-muenchen.de/~robert/freetype.html -
Thanks to the MPEG Software Simulation Group, for -libmpeg, the -
MPEG-2 Encoder/Decoder -
-mssg@mpeg.org -
http://www.mpeg.org/MSSG/ -
Thanks to Heroine for quicktime4linux -a quickime Decoder -and libmpeg3, another MPEG-2 Encoder/Decoder -
MPEG-2 Encoder/Decoder -
-mssg@mpeg.org -
http://heroinewarrior.com/ -
Thanks to LCS/Telegraphics for Wintab, the Windows -tablet library. -
-wintab@pointing.com -
Thanks to David McAllister for the Particle System -library. -
-davemc@cs.unc.edu -
http://www.cs.unc.edu/~davemc/Particle/ -
Thanks to John Stone for the Space Orb library, -libOrb -
-j.stone@acm.org -
http://www.umr.edu/~johns/projects/liborb/ -

---- -
1.10) Are there any restrictions on GEM? -

GEM is under the Gnu Public License. This basically -means that it will always be free software.Check out http://www.gnu.org -for more information and read the full license in GnuGPL.LICENSE in the GEM release. -

---- -
1.11) How do I use GEM in a performance? -

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. -

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. -

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 question 2.12, 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. -

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(".
-Note: 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) -

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 <render.host>:0.0" - -

If you are doing audio with graphics, the only solution -to prevent clicking (question 5.1) 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. -

-

USING GEM

-
2.1)How do I (???) -

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. -

2.2) How do I make GEM run? -

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 -

/usr/people/mdanks/pd/bin/pd -lib /usr/people/mdanks/pd/gem/Gem -

and on WinNT -

\pdDir\pd\bin\pd -lib /pdDir/pd/gem/Gem -

on UNIX-systems you will probably want to use a .pdrc file, - where you can put the command-line arguments for pd that you "always" need. -

If you don't see a startup message from GEM, then something went wrong. -

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. -

---- -
2.3) Why doesn't GEM run? -

Notice that the -lib flag always requires Unix -styles slashes. This is the case even on Windows. -

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). -

---- -
2.4) I've got it running. Now what? -

Try out the manual. It will step you through -the basics. -
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 -gem/01.basic/01.redSquare.pd -It puts a red square up on the screen and allows you to rotate it. gemImage.pd -shows how to load in a TIFF file. gem/03.lighting/04.moveSpheres.pd -moves two spheres around the screen. Try the other ones. -
Most of the GEM objects have test patches which -give some information about the various controls for the object. -

---- -
2.5) On IRIX 5.3, why does GEM dump with an rld error? -

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. -
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. -

---- -
2.6) Why can't I compile GEM on IRIX 5.3? -

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. -

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. -

---- -
2.7) Why is GEM slow in general? -

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). -
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. -
profile 0 - turn off profiling -
profile 1 - turn on profiling -
profile 2 - turn on profiling -and don't cache pixes -

---- -
2.8) Why is GEM slow on IRIX? -

If you are having major slowdowns, then please let -me know. I have gotten very good performance on most machines (Indy, -O2, Impact, Onyx2). -

---- -
2.9) Why is GEM slow on WinNT/Win95? -

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. -
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. -

---- -
2.10) Why is GEM slow on Linux? -

It is because you have to use Mesa, which might be -running iin software. Mesa (http://www.mesa.org) -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. -
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) -
radeon cards should also be supported very well under linux (even with open-source drivers) -

---- -
2.11) If I resize the window, everything looks strange. -

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. -

---- -
2.12) Can GEM run on a 3Dfx Voodoo card? -

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. -

IMPORTANT: You MUST set the environment variable -

GEM_SINGLE_CONTEXT = 1 -

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. -
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. -

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. -

---- -
2.13) Will GEM support hardware transform and lighting -(T & L)? -

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. -

2.14) I get an error "GEM needs Truecolor visual -support". -

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 -

startx -- -bpp 16 -

or some higher number, then it should work fine. 32-bit color -is the best. -

-

VIEWING OBJECTS

-
3.1)Why does everything seem dim?< -

You probably turned on lighting but don't have any -lights in the world. Either add a light with world_light or -light -or turn lighting off by sending a message 'lighting 0' to the gemwin. -You can also send a reset message to gemwin to set it back to the -startup state (which doesn't have any lighting). -

---- -
3.2) Why does everything seem dark? -

See question 3.1. -
If you are using view 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. -
Also, if you have been using single buffering ('buffer -1' message to gemwin), then you might still be in that mode. -Either send a 'buffer 2' message or a 'reset' message to gemwin. -Then, destroy and create your window. -

-

TEXTURE MAPPING

-
4.1) My image doesn't appear. What is going -on? -

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. -

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. -

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 pix_coordinate 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). -

Also, make sure that GEM can find your image (ie, -that the path name is correct). -

---- -
4.2) My image looks strange. What is going -on? -

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. -
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). -

---- -
4.3) Why does GEM say that it can't handle a gray -image? -

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 native -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 pix_rgba -or harass whoever made the object to add the functionality. -

---- -
4.4) What image formats can GEM handle? -

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). -

GEM can write TIFF and JPEG images. -TIFF-images will be full RGBA-images, wheras JPEG-files only support (compressed) RGB. -

---- -
4.5) What movie formats can GEM handle? -

The movie formats GEM can handle (still) depend on the platform -you are using. -

On Windoze you can read all AVI-files you have codecs for -

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 to me. -(Be ready to upload the movie-file that won't work) -

---- -
4.6) Why is pix_draw so slow? -

pix_draw is almost never hardware accelerated -on PCs graphics accelerator. This means that it runs extremely -slowly. Always use pix_texture, even if you are just displaying -an image. -

-

WORKING WITH PD

-
5.1) Why do I get clicks in the audio? -

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). -
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 netsend and netreceive -to have the two versions of Pd talk to each other. -

---- -
5.2) How do I get audio data to GEM? -

One simple way to get raw audio values right now is -to use snapshot~. Just set up a metro which bangs snapshot~ -and use the floating point value. If you want "musical" information, -then use objects such as env~. -You might also have a look at the pix_sig2pix~ which interprets audio-data as pixels -and its counterpart pix_pix2sig~ -

---- -
5.3) Why can't GEM find an image/model file? -

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 -path flag. -

Check the following: -

1) Does the file exist? -
2) Did you make a typo in the filename? -
3) Is the file in the search-path ? -

---- -
5.4) How can I optimize my patches? -

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... -
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 spigot or gate and block -the events early. This is especially important with objects that -send a lot of numbers, like ~ objects or line/tripleLine. -

-

WRITING NEW GEM OBJECTS

-
6.1) How do I write a new GEM object? -

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. -

---- -
6.2) What are the default OpenGL states? -

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 -

float xDivy = (float)m_width / (float)m_height; -
glMatrixMode(GL_PROJECTION); -
glLoadIdentity(); -
glFrustum(-xDivy, xDivy, -1.0, 1.0, 1.0, 20.0); -
gluLookAt(0.0, 0.0, 4.0, 0.0, 0.0, 0.0, 0.0, 1.0, -0.0); -
glMatrixMode(GL_MODELVIEW); -
glViewport(0, 0, m_width, m_height); -

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. -

The specific functions to look at are: -

GemMan::windowInit() -
GemMan::resetValues() -
gemhead::renderGL() -

-

OBJECT SPECIFIC

-
7.1) Why doesn't <object> exist on <platform>? -

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...) -

---- -
7.2) Why doesn't gemtablet work? -

gemtablet only works on WinNT. I don't -have drivers for IRIX or Linux (also, see question 7.4) -
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. -
The tablet is mapped to the size of the GEM graphics -window. -

--- -
7.3) I don't want GEM to take over my tablet. -How do I stop it? -

Set the environment variable -

GEM_NO_TABLET = 1 -

---- -
7.4) Why doesn't gemmouse work in IRIX? -

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). -

---- -
7.5) Why doesn't gemorb work? -

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. -
<RANT> When will companies wake up and actually -provide drivers and support for their products under WinNT? </RANT> -

---- -
7.6) What is wrong with pix_video in WinNT? -

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. -

[return] -
-
- - + + + + + + + Gem FAQ + + + +

+

+GEM FAQ

+ +


* : new question +
+ : changed question +

+

+QUESTIONS

+GENERAL +
1.1) What is GEM? +
1.2) What is Pd? +
1.3) What platforms do GEM and Pd run on? +
1.4.0) How do I install GEM and Pd on IRIX? +
1.4.1) How do I install GEM and Pd on linux? +
1.4.2) How do I install GEM and Pd on WinNT? +
1.7) What is a good intro to OpenGL? +
1.8) Are there any web sites for Pd or GEM? +
1.9) What libraries does GEM use? (aka: Who does Mark +want to thank?) +
1.10) Are there any restrictions on GEM? +
1.11) How do I use GEM in a performance? +

USING GEM +
2.1) How do I (???) +
2.2) How do I make GEM run? +
2.3) Why doesn't GEM run? +
2.4) I've got it running. Now what? +
2.5) On IRIX 5.3, why does GEM dump with an rld error? +
2.6) Why can't I compile GEM on IRIX 5.3? +
2.7) Why is GEM slow in general? +
2.8) Why is GEM slow on IRIX? +
2.9) Why is GEM slow on WinNT/Win95? +
2.10) Why is GEM slow on Linux? +
2.11) If I resize the window, everything looks strange. +
2.12) Can GEM run on a 3Dfx Voodoo card? +
2.13) Will GEM support hardware transform and lighting +(T&L) ? +
2.14) I get an error "GEM needs Truecolor visual support". +

VIEWING OBJECTS +
3.1) Why does everything seem dim? +
3.2) Why does everything seem dark? +

TEXTURE MAPPING +
4.1) My image doesn't appear. What is going on? +
4.2) My image looks strange. What is going on? +
4.3) Why does GEM say that it can't handle a gray image? +
4.4) What image formats can GEM handle? +
4.5) What movie formats can GEM handle? +
4.6) Why is pix_draw so slow? +

WORKING WITH PD +
5.1) Why do I get clicks in the audio? +
5.2) How do I get audio data to GEM? +
5.3) Why can't GEM find an image/model file? +
5.4) How can I optimize my patches? +

WRITING NEW GEM OBJECTS +
6.1) How do I write a new GEM object? +
6.2) What are the default OpenGL states? +

OBJECT SPECIFIC +
7.1) Why doesn't <object> exist on <platform>? +
7.2) Why doesn't gemtablet work? +
7.3) I don't want GEM to take over my tablet. +How do I stop it? +
7.4) Why doesn't gemmouse work in IRIX/Linux? +
7.5) Why doesn't gemorb work? +
7.6) What is wrong with pix_video in WinNT? +

+

+ANSWERS

+

GENERAL

+
1.1) What is GEM? +

GEM is the Graphics Environment for Multimedia. +It was originally written by Mark Danks 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. +

You can get GEM at http://gem.iem.at/ +

GEM was sponsored by a grant from Intel (http://www.intel.com) +

GEM was ported to linux by Günter Geiger +

GEM is now maintained by IOhannes m zmölnig. +

the core-development team consists of

+lots of contributions are made by various people (thanks to all of them) +

---- +
1.2) What is Pd? +

Pd is a real-time environment for audio and MIDI. +It was written by Miller Puckette, 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. +

You can get Pd at http://www.crca.ucsd.edu/~msp/software.html +

Pd is sponsored by a grant from Intel (http://www.intel.com) +

---- +
1.3) What platforms do GEM and Pd run on? +

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). +Günter Geiger +has done an initial port of GEM and Pd to Linux http://gige.epy.co.at). +

GEM is now maintained by me and +developed by a team of several independent programmers (see section 1.1) +

---- +
1.4) How do I install GEM ? +

---- +
1.4.0) How do I install GEM and Pd on IRIX? +

See the readme for installing Pd. +

GEM should be at +

pd/gem +

If you run GEM.INSTALL.sh, then all of the example files and documention +should be put in the correct locations. +

---- +
1.4.1) How do I install GEM and Pd on linux? +

See the readme for installing Pd. +

GEM should be at +

chdir to <gem>/src/Gnu and build Gem following the instructions in the README.build +(./configure; make) +

If you then make install, then all of the example files and documention +should be put in the correct locations. +

if you are using debian, Gem should be available via apt

+

if you are using an rpm-based distribution, check out the builds at planetCCRMA

+

---- +
1.4.2) How do I install GEM and Pd on WinNT? +

See the readme for installing Pd. +

unzip GEM so that it is at +

pd\gem +

If you run GEM.INSTALL.bat, then all of the example files and documentation +should be put in the correct locations. +

there is also an installer for windows. +

---- +
1.4.3) How do I install GEM and Pd on macOS? +

See the readme for installing Pd. +

there is also an installer for macOS. +

---- +
1.7) What is a good intro to OpenGL? +

The best book is the OpenGL Programming Manual +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 +http://www.opengl.org. +Also, Mark Kilgard (who used to work for SGI) has a wonderful site with +lots of links (http://reality.sgi.com/mjk) +Also, Normal Lin has written another great book on 3D-graphics under linux +

---- +
1.8) Are there any web sites for Pd or GEM? +

Except for the ones noted above, there is the Japanese +installation page at +
http://www.rinc.or.jp/~kotobuki/gem/index.htm +

There is a Pd mailing list. Subscription info +is on IEM's site http://www.iem.at/mailinglists/pd-list +

One of pd's unofficial home-pages is at http://pd.iem.at hosted by the +Institute of Electronic Music and Acoustics, Graz, Austria +

Also hosted by the iem is the site of the pd-community +http://www.puredata.info +

An interesting place might also be Günter Geiger's size http://gige.epy.co.at/ +

there are lot's of other cool pages (search the net...) +

---- +
1.9) What libraries does GEM use? +(aka: Who does Mark want to thank?) +

All copyrights and license info can be found in +
GEM.LICENSE.TERMS +
Thanks to Sam Leffner for libTiff, the TIFF image +loader. +
+sam@engr.sgi.com +
ftp://ftp.sgi.com/graphics/tiff/ +
Thanks to Masayuki Matsumoto for fstimage for OpenGL, +the SGI +
image loader. +
+matumot@dst.nk-exa.co.jp +
Thanks to the Independent JPEG Group for libjpeg, +the JPEG image loader. +
+jpeg-info@uunet.uu.net +
ftp://ftp.simtel.net/pub/simtelnet/msdos/graphics/ +
Thanks to Mark Kilgard at al. (and SGI) for glut, the openGL Utility Toolkit +
http://www.pobox.com/~ndr +
Thanks to Stephane Rehel for GLTT, the OpenGL TrueType +render. +
+rehel@worldnet.fr +
http://home.worldnet.fr/~rehel/gltt/gltt.html +
Thanks to David Turner, Robert Wilhelm, and Werner +Lemberg for +
Freetype, a TrueType font +rendering engine. +
+turner@enst.fr +
+robert@physiol.med.tu-muenchen.de +
+a7971428@unet.univie.ac.at +
http://www.physiol.med.tu-muenchen.de/~robert/freetype.html +
Thanks to the MPEG Software Simulation Group, for +libmpeg, the +
MPEG-2 Encoder/Decoder +
+mssg@mpeg.org +
http://www.mpeg.org/MSSG/ +
Thanks to Heroine for quicktime4linux +a quickime Decoder +and libmpeg3, another MPEG-2 Encoder/Decoder +
MPEG-2 Encoder/Decoder +
+mssg@mpeg.org +
http://heroinewarrior.com/ +
Thanks to LCS/Telegraphics for Wintab, the Windows +tablet library. +
+wintab@pointing.com +
Thanks to David McAllister for the Particle System +library. +
+davemc@cs.unc.edu +
http://www.cs.unc.edu/~davemc/Particle/ +
Thanks to John Stone for the Space Orb library, +libOrb +
+j.stone@acm.org +
http://www.umr.edu/~johns/projects/liborb/ +

---- +
1.10) Are there any restrictions on GEM? +

GEM is under the Gnu Public License. This basically +means that it will always be free software.Check out http://www.gnu.org +for more information and read the full license in GnuGPL.LICENSE in the GEM release. +

---- +
1.11) How do I use GEM in a performance? +

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. +

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. +

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 question 2.12, 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. +

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(".
+Note: 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) +

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 <render.host>:0.0" + +

If you are doing audio with graphics, the only solution +to prevent clicking (question 5.1) 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. +

+

USING GEM

+
2.1)How do I (???) +

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. +

2.2) How do I make GEM run? +

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 +

/usr/people/mdanks/pd/bin/pd -lib /usr/people/mdanks/pd/gem/Gem +

and on WinNT +

\pdDir\pd\bin\pd -lib /pdDir/pd/gem/Gem +

on UNIX-systems you will probably want to use a .pdrc file, + where you can put the command-line arguments for pd that you "always" need. +

If you don't see a startup message from GEM, then something went wrong. +

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. +

---- +
2.3) Why doesn't GEM run? +

Notice that the -lib flag always requires Unix +styles slashes. This is the case even on Windows. +

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). +

---- +
2.4) I've got it running. Now what? +

Try out the manual. It will step you through +the basics. +
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 +gem/01.basic/01.redSquare.pd +It puts a red square up on the screen and allows you to rotate it. gemImage.pd +shows how to load in a TIFF file. gem/03.lighting/04.moveSpheres.pd +moves two spheres around the screen. Try the other ones. +
Most of the GEM objects have test patches which +give some information about the various controls for the object. +

---- +
2.5) On IRIX 5.3, why does GEM dump with an rld error? +

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. +
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. +

---- +
2.6) Why can't I compile GEM on IRIX 5.3? +

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. +

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. +

---- +
2.7) Why is GEM slow in general? +

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). +
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. +
profile 0 - turn off profiling +
profile 1 - turn on profiling +
profile 2 - turn on profiling +and don't cache pixes +

---- +
2.8) Why is GEM slow on IRIX? +

If you are having major slowdowns, then please let +me know. I have gotten very good performance on most machines (Indy, +O2, Impact, Onyx2). +

---- +
2.9) Why is GEM slow on WinNT/Win95? +

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. +
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. +

---- +
2.10) Why is GEM slow on Linux? +

It is because you have to use Mesa, which might be +running iin software. Mesa (http://www.mesa.org) +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. +
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) +
radeon cards should also be supported very well under linux (even with open-source drivers) +

---- +
2.11) If I resize the window, everything looks strange. +

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. +

---- +
2.12) Can GEM run on a 3Dfx Voodoo card? +

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. +

IMPORTANT: You MUST set the environment variable +

GEM_SINGLE_CONTEXT = 1 +

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. +
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. +

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. +

---- +
2.13) Will GEM support hardware transform and lighting +(T & L)? +

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. +

2.14) I get an error "GEM needs Truecolor visual +support". +

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 +

startx -- -bpp 16 +

or some higher number, then it should work fine. 32-bit color +is the best. +

+

VIEWING OBJECTS

+
3.1)Why does everything seem dim?< +

You probably turned on lighting but don't have any +lights in the world. Either add a light with world_light or +light +or turn lighting off by sending a message 'lighting 0' to the gemwin. +You can also send a reset message to gemwin to set it back to the +startup state (which doesn't have any lighting). +

---- +
3.2) Why does everything seem dark? +

See question 3.1. +
If you are using view 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. +
Also, if you have been using single buffering ('buffer +1' message to gemwin), then you might still be in that mode. +Either send a 'buffer 2' message or a 'reset' message to gemwin. +Then, destroy and create your window. +

+

TEXTURE MAPPING

+
4.1) My image doesn't appear. What is going +on? +

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. +

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. +

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 pix_coordinate 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). +

Also, make sure that GEM can find your image (ie, +that the path name is correct). +

---- +
4.2) My image looks strange. What is going +on? +

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. +
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). +

---- +
4.3) Why does GEM say that it can't handle a gray +image? +

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 native +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 pix_rgba +or harass whoever made the object to add the functionality. +

---- +
4.4) What image formats can GEM handle? +

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). +

GEM can write TIFF and JPEG images. +TIFF-images will be full RGBA-images, wheras JPEG-files only support (compressed) RGB. +

---- +
4.5) What movie formats can GEM handle? +

The movie formats GEM can handle (still) depend on the platform +you are using. +

On Windoze you can read all AVI-files you have codecs for +

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 to me. +(Be ready to upload the movie-file that won't work) +

---- +
4.6) Why is pix_draw so slow? +

pix_draw is almost never hardware accelerated +on PCs graphics accelerator. This means that it runs extremely +slowly. Always use pix_texture, even if you are just displaying +an image. +

+

WORKING WITH PD

+
5.1) Why do I get clicks in the audio? +

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). +
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 netsend and netreceive +to have the two versions of Pd talk to each other. +

---- +
5.2) How do I get audio data to GEM? +

One simple way to get raw audio values right now is +to use snapshot~. Just set up a metro which bangs snapshot~ +and use the floating point value. If you want "musical" information, +then use objects such as env~. +You might also have a look at the pix_sig2pix~ which interprets audio-data as pixels +and its counterpart pix_pix2sig~ +

---- +
5.3) Why can't GEM find an image/model file? +

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 -path flag. +

Check the following: +

1) Does the file exist? +
2) Did you make a typo in the filename? +
3) Is the file in the search-path ? +

---- +
5.4) How can I optimize my patches? +

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... +
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 spigot or gate and block +the events early. This is especially important with objects that +send a lot of numbers, like ~ objects or line/tripleLine. +

+

WRITING NEW GEM OBJECTS

+
6.1) How do I write a new GEM object? +

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. +

---- +
6.2) What are the default OpenGL states? +

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 +

float xDivy = (float)m_width / (float)m_height; +
glMatrixMode(GL_PROJECTION); +
glLoadIdentity(); +
glFrustum(-xDivy, xDivy, -1.0, 1.0, 1.0, 20.0); +
gluLookAt(0.0, 0.0, 4.0, 0.0, 0.0, 0.0, 0.0, 1.0, +0.0); +
glMatrixMode(GL_MODELVIEW); +
glViewport(0, 0, m_width, m_height); +

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. +

The specific functions to look at are: +

GemMan::windowInit() +
GemMan::resetValues() +
gemhead::renderGL() +

+

OBJECT SPECIFIC

+
7.1) Why doesn't <object> exist on <platform>? +

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...) +

---- +
7.2) Why doesn't gemtablet work? +

gemtablet only works on WinNT. I don't +have drivers for IRIX or Linux (also, see question 7.4) +
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. +
The tablet is mapped to the size of the GEM graphics +window. +

--- +
7.3) I don't want GEM to take over my tablet. +How do I stop it? +

Set the environment variable +

GEM_NO_TABLET = 1 +

---- +
7.4) Why doesn't gemmouse work in IRIX? +

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). +

---- +
7.5) Why doesn't gemorb work? +

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. +
<RANT> When will companies wake up and actually +provide drivers and support for their products under WinNT? </RANT> +

---- +
7.6) What is wrong with pix_video in WinNT? +

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. +

[return] +
+
+ + -- cgit v1.2.1