[PD] Getting started with GEM

[chris clepper]

>Hello all,
>
>I have gotten a chance to install GEM, I am using the GemG4 compiled 
>version. I also downloaded the OSX Docs (pd files). I also read the 
>online docs (html files), but I still don't understand exactly how 
>things are put together to actually get an image/movie rendered.
>
>Could someone point me to an example file that allows me to open an 
>image or movie, and does some arbitrary processing. I was able to 
>open a couple of images with a few of the help files

In the pix directory of the standard GEM examples you will find a 
patch 05.pix_film which loads a film and does some convolution.  I 
haven't gotten to the texturing and film playing tutorials yet but I 
hope to have those done over the weekend (I did write a lighting 
tutorial today though).

>What format of files can Gem read? I tried several MPG files, it 
>displays the first frame, but nothing else.

On OSX GEM reads just about anything Quicktime reads with the 
exception of MPEG-1 files.  For some reason QT treats MPEG-1 files as 
one frame so nothing gets played in GEM.  It's unclear whether this 
is a bug in QT or GEM uses the wrong code to play the file.  The QT 
docs have the exact same code we tried in GEM but it doesn't work.

>I also opened up the 'yuv_feedback' help file, but it seems that 
>there is no object named 'yuv_feedback'.

yuv_feedback never really existed, it became pix_blur.  For the most 
part the yuv_ objects are dead and the code rolled into pix_.

>Eventually, I would like to render/plot some fractals. I was reading 
>the Geos function, but there doesn't seem to be a way to access the 
>image on a pixel level. Or is there some other way to access and 
>manipulate the individual pixels in an image.

The Geos are OpenGL objects not made up of pixels, but vertices and 
texture coordinates.  Do you want to get the pixel data of the Geos, 
a film/image, or the window buffer?  The first isn't really possible, 
the second can be done with pix_dump, and the third with glReadPixels 
(pix_snap if it's working).  As for the fractals, there might be an 
example of making fractals using OpenGL somewhere on the web.  It 
would surprise me if no one had ever done this before.  There might 
be some really insane possibilities making fractals out of 3D 
vertices.

>
>Thanks,
>
>Mike
>
>
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