I am interested in using a small portable computer device for simple generative 3d visuals (loading 3d objects, adding simple .png textures).

I was considering a used Mac Mini, but a RPI seems possible as well. I am aware it would be pushing the limits of the RPI, but would it be feasible at all? Other than the CPU strain, I have read elsewhere that the OpenGL status of the RPI is hazy for GEM support

If I'm not mistaken Pi uses OpenGL ES and not OpenGL which makes it incompatible with Gem. OpenFrameworks on the other hand have make a port for ARM based processors. I remember rendering a square with Gem on a UDOO a few years ago, but not sure where this whole ARM processor and Gem thing is right now.

Since a beta OpenGl driver has been released in Rasbian, you can use gem objects with a decent framerate now if you enable it in raspi-config. I even tried a basic blob tracking and it was working quite well...

I remember having GUI issues with pd 0.47 and with the beta driver enabled.

I never used a raspberry pi, but am following with much interest the developement in media. Maybe your odds are not to bad: experimental openGL support.
I would be very interested in the results.

If the beta driver for OpenGL, along with the RPI hardware, can run the games in the link Johnny Mauser posted... it seems good enough for my GEM purposes

I´d be really interested if somebody managed to run GEM/PD on a Raspi ...and how! Could you maybe share your raspi-image? Still struggeling to get PD running

Gem works but rendering frames is really slow so what i have been doing is setting buffer to 1 and banging gemhead with a metro object so i can set the render rate.

you can either use [declare -stdlib Gem] in your patch or load Gem on startup from File/Preferences/Startup.

if you are having trouble installing pd itself these are the steps i followed to install:
most of this is from the README.txt and INSTALL.txt files in the Pd folder. you can check those files for more information.)

Start by opening a commandline shell:
and entering the following:

sudo apt-get install build-essentials automake autoconf libtool gettext

sudo apt-get install libasound2-dev

then navigate to the Pd source directory:

    cd path/to/pd

./autogen.sh
./configure 

make
sudo make install

Additionally I did have to install tcl/tk using:

sudo apt-get install tk

you can then open pd from the command line
by entering
pd

Simply switch openGl driver ON in raspi-config, then it's a lot faster.

Better use raspbian Stretch I think, because in older Raspbian version, pd and OpenGl rendering looks buggy in the patch's view (Maybe TCL graphic rendering problem: no pathchcoords )

@60htz thanks,
any other config setting changes you recommend for audio or video.

p.s. still having to bang the gemhead to actually render frames when using pix_video. is there another message to automatically play at framerate ? toggling the gemhead does nothing..

Just wanted to give a clear and concise answer to the original question.

I just installed pd vanilla on my Raspberry Pi 3 and managed to get Gem running at normal speed, no need to make any changes to my system.