Weblog -- Computer Graphics

By Paul Quek (e-mail: quekpaul@hotmail.com), in Singapore

Surface Evolver Version 2.14 (August 18, 1999) -- by Ken Brakke

Ken Brakke's Surface Evolver  is an interactive program for the modelling of liquid surfaces shaped by various forces and constraints. The program is available free of charge and can be downloaded from http://www.geom.umn.edu/software/evolver/#download for various platforms.

I tried the MS-Windows NT/98/95 version ( evolver.exe ) with an example tutorial file called cube.fe, which can be obtained from http://www.geom.umn.edu/software/evolver/html/cube.htm -- to create cube.fe, just cut-and-paste from cube.htm using your favorite text editor, then ( while at Windows Explorer ) associate cube.fe with evolver.exe , and double-click cube.fe to run it.

The UI is pretty basic for a Windows program, but as Brakke explains it, this is his first Windows program, so there isn't any bells and whistles (e.g., no pull-down menus, etc.) -- basically, evolver.exe runs like a "DOS box" ( or "command prompt" box, if you are using Windows XP ).

Anyway, the program identifies itself as Surface Evolver Version 2.14 August 18, 1999; Windows NT/95/98 OpenGL  -- as you can see, it supports the OpenGL graphics library -- and there is a very simple command prompt as follows:

Enter command:

When I type in "s" at the Enter command:  prompt, meaning "show the surface of the cube, as specified in cube.fe", a new window pops up and in that window, as explained in cube.htm:

You should see a square divided into four triangles by diagonals. This is the front side of the cube; you are looking in along the positive x-axis, with the z axis vertical and the positive y axis to the right. On some systems, you can manipulate the displayed surface with the mouse (particularly Windows NT/95/98; hit the 'h' key with the mouse focus in the graphics window to get a summary of the possibilities).

This program is great: I point the mouse on the cube in the new window, and can rotate the cube by simply moving the mouse. Very nice!

Thanks to Ken Brakke.

Monday, 06 January 2003 -- Video & Still-Image Manipulation

VCR Tape to Video CD (VCD) Conversion

    After a really really late dinner and the usual ablutions, I reviewed a tape recording of the cable programmes from the Discovery Channel while automatically converting the tape-recorded programmes to VCD recordings via the Terapin VCD Recorder, which is an off-line piece of equipment (that is, not connected to any of my PCs). Each of the resulting VCDs contains a MPEGAV directory, which holds a file entitled MUSIC01.DAT ( for multi-recording sessions on the same VCD, there would be MUSIC02.DAT, MUSIC03.DAT and so on ).







VCD (in "DAT" format) to MPEG Conversion

    Then, I did a VCD-to-mpg conversion via the quite useful software VCDCutter. That is, from the MPEGAV directory on the VCD, the VCD's MUSIC01.DAT file -- which is the default filename created by the Terapin VCD Recorder -- is converted by VCDCutter to DIV00001.MPG on my hard disk. DIV00001.MPG, DIV00002.MPG, and so on are the default filenames created by VCDCutter.

    So, now, I have a mpeg file (DIV00001.MPG) on my hard disk, which can be viewed with any of the newer media players, such as Windows Media Player ( I am using version 7 and 8 on different PCs, although version 9 is already out ) or Global DIVX Player ( version 1.9.1 works just fine! ). Then, I wonder, "Now, what?"







Multi-Frame Extraction: Chopping Up A MPEG File

    Hmm ... wonder if I could "chop up" a long MPEG file into smaller files ... a sort of "multi-frame extraction", if you like. One can, perhaps, use the term "clip extraction", since a "clip" can refer to several movie frames. Sorry, I have yet to bone up on video editing terms!

    Anyway, I did a Yahoo! search of the Net for a mpeg editor, and found the demo version of the Honestech MPEG Editor Version 4, which has a limit of 5 minutes for mpg files being produced, but since I wasn't really interested in producing a long mpeg movie, that limitation didn't bother me ... the Honestech MPEG Editor did the job alright, allowing me to cut out those parts of the DIV00001.MPG file that I wanted -- most of these smaller mpeg files were smaller than 0.5MB ... which means I could easily upload them to the Net or e-mail them via the Net ...

    Actually, the software VCDCutter could have done the chopping-up job, but it had limitations because of its shareware nature ... You could save only a small mpeg file ( called "clips" ), but it would only be 7-8 seconds long ... Too bad! The demo version of the Honestech MPEG Editor Version 4 can produce 5-minute long mpeg files.

    Now, I wondered if I could convert individual frames of the smaller mpeg files ( or even the original DIV00001.MPG ) to still images ... that is, into BMP or JPG or TGA or even the poorer-resolution GIF still-image formats ...

    So, back to the Net ... Surfed it for a while ( read up several websites from the previous Yahoo! search for a mpeg editor ) and found a expertsXexchange posting where someone claimed you could chop up a mpeg file into smaller mpeg files by using Adobe Premier version 5.0 ...

    Hey ... doesn't the software VCDCutter have the ability to do this "single frame extraction" ...? I tried it, and found it a real pain ...

    Gave up for the night and went to snooze-land.

Tuesday, 07 January 2003 -- Single-Frame Extraction: Producing Still-Image Files

    Today, I re-did the Yahoo! search for a mpeg editor ( where previously I had found many websites/webpages describing the Honestech MPEG Editor Version 4 ), then re-read the expertsXexchange posting (where someone had claimed you could chop up an mpeg file into smaller mpeg files by using Adobe Premier version 5.0), and decided to do a Yahoo! search for Adobe Premier and found the official Adobe website, where I got the Version 6 Tryout ( the setup file, pre60to.zip, is about 70MB in size! ), which will expire in 30 days ... Sigh!

    Anyway, after setting up the software, I found that, in Adobe Premier version 6 Tryout, I could easily pause a mpeg file at any frame and then "Export Clip" ( under the "File" menu ) the selected individual frame as a still image, in say, BMP format.

    After that, any old ( or better, still new ) image editor -- even Windows Paint -- could do whatever you want to do with the still image, including cropping whatever section of the image you want. Naturally, conversion to other still-image file formats -- say, JPG -- is child's play. Adobe Premier could really do the job of producing still images from a mpeg file ( i.e., "single-frame extraction" ) -- the learning curve was almost non-existent! Great software!

Postscripts:

1. Actually, Adobe Premier does allow you to perform multi-frame extraction, or clip extraction, from a MPEG file -- that is, produce short movies from longer movies -- so that there was really no need to use any other software, except that Adobe Premier saves to .AVI file! Still, you can convert the .AVI file to, say, a mpeg file -- I wouldn't recommend it, though, as it takes too long. Better stick to using the Honestech MPEG Editor to produce shorter mpeg clips from large mpeg files.
   
   
2. Additionally, Adobe Premier can also "Export Clip" ( under the "File" menu ) to audio file ( only .AVI, I think ), or better still under "Advanced Windows Media ..." ( from "Export Clip" ) you could, I understand, convert to other audio formats .... or you can explore "Save for Web..." ( again, from "Export Clip" ) ..., somewhere along the way, Cleaner EZ is automatically activated ??? This is getting a little too involved! But with this, you can produce, for example, a "wmv" file from your shorter mpeg clip ( note: "wmv" files appears to be highly compressed and meant for "streaming" across the Net ).
   
   
3. VCDCutter also allows converting the MUSIC01.DAT file ( from the VCD ) directly to an audio ( i.e., MP3 ) file, but it would be a large .MP3 file! After that, you can use dbPowerAMP Music Converter ( which is a really great favorite of mine ) to easily convert the .MP3 file to a WAVE file ( using Winamp to do music file conversion was a pain as you've got to read up on the help file and then do some tweaking here and there! ). After that, editing the .WAV file would be a snap with your favorite wave editor. After you have done whatever magic you want to do with the wave file, you can always use dbPowerAMP Music Converter to convert the wave file back to a .MP3 file. Then, if you like, you can burn all the .MP3 files you want onto a CD-R or CD-RW, and play that CD-R or CD-RW on your hi-fi, which must support .MP3 playback, of course! .

24 March 2003 -- Graphics from Video Sources

Okay, here are some graphics/video/AV stuff I have "cobbled" together, just for the "exploration" experience and for the "fun of the process" ... :

NGC Graphics

Personal Computers  in tripod.com