[GEM-dev] gem port to opengl-es - initial developments..

[dmotd]

hi gem folks,

i've had a bit of free time to begin porting gem to opengl-es. 

i'm building and testing with a nokia-n900/RX51 tablet - a debian based
arm arch which supports both opengl-es 1.1 common and opengl-es 2.0.

initial hacking is concentrated on opengl-es 1.1, which is generally
compatible to the opengl 1.0 spec. opengl-es 2.0 uses shaders to replace
fixed functions so there is a lot more work involved in replacing core
gem functions.

i'm using the egl spec for windowing/surface/buffer support, it is cross
platform (although afaik apple uses its own modification 'aegl'). it
provides basic functionality for reading and writing gl functions to
buffer (along the lines of glx), and like glx still relies on operating
system apis to supply other interfaces (keyboard / mouse etc).

so far: 
--
cloned gem git, checkout 0.93 tag, created es branch.

using glues for basic (incomplete) glu functionality

using libglutes for basic (incomplete) glut functionality 

added additional autoconf tricks to find and test libraries

merged the latest git ES branch of GLEW which has experimental support
for GLES/EGL 

added egl drop in for GemWinCreate

successful build against pd-0.43 using enable-Controls and others
disabled.
--

reports: 
--
libxxf86vm doesn't seem to work properly on the tablet, so for the time
being the window modelines are hard coded. there are some other window
manager hints that are specific to the device too.

gemwin successfully creates the egl window buffer and rendering context.

gem crashes when glClearDepthf and glFrustumf are called (both are
floating-point variations to the base GL functions and part of the GL-ES
spec). furthermore looking at the output of 'nm -C Gem.pd_linux' shows
that these functions are not present in the compiled lib, what does this
mean?

commenting these functions out allows the gemwin to complete init and
create successfully. a call to render causes a crash somewhere in the
rendering chain (GemMan::render), but i have had little success
debugging this issue.
--

notes:
--
i'm developing with an eye on the raspberry pi project which should
bring affordable opengl-es architecture to a small form factor, perfect
for installations of (audio)visual artwork - but there's no reason why
any recent (jailbroken) mobile/tablet technologies wouldn't be
applicable for creative repurposing. 

before anyone get's excited, the apple 'app store' is still afaik not
compatible with gpl code, so it is unlikely there will be a 'rjdj' style
app using gem, or likewise any gem based vj app, i don't think the same
can be said for google's android platform, but i'm not a user or
developer of said platform (or the fruit for that matter).

i am coding on a linux-amd64 pc, cross-compiling in scratchbox and
testing on the device, using git/scp as a go-between.. this is a bit
cumbersome/inefficient - can anyone suggest a virtual machine image
(linux based) that provides a graphical gl-es environment and a minimal
editor/ide to build and test with? 
--

i'll keep everyone up to speed as i make developments, and if anyone can
replicate my dev environment and wants to contribute i'll happily push
to a public git sooner rather than later.

cheers,
dmotd