Hi All,
I'm delighted to announce that as of today I'm now working on porting
the OpenSceneGraph to work on OpenGL ES 2.0 ;-)
I'll be working on this through this month, and likely into November
to tie up all the loose ends, and get the work integrated into
svn/trunk and then into a stable release of the OpenSceneGraph. I
have had to start this round of work immediately after completing
other client work so haven't had a window opportunity to catch up with
submissions and go for making 2.10 as I had originally hoped. If
community members are keen to see a 2.10 release sooner rather than
later then we'll need to rely upon other members of the community to
take charge of a 2.10 branch and push it all the way to release
without me at the helm. When might later be? If things go well
then we could potentially have OpenGL ES 2.0 support into svn/trunk
and ready for a stable release for the end of November. I'll be
making a dev release prior to making the OpenGL ES branch, so perhaps
this will suffice if you need a release to work against. If you want
to help make 2.10 this month then please raise you hand and we can
strike up a separate thread to look at the practicalities of making
this happen without me at the helm.
My plan for the OpenGL ES work itself will be to keep it as straight
forward as I can, looking to minimize the number of API changes and
implementation changes to the OSG code base. This approach will be
key to progressing the task quickly and enabling the new code to be
merged into svn/trunk early in the development cycle and to avoid
disrupting the traditional OSG/OpenGL user base as much as possible.
What I won't be attempting to do is provide sophisticated tools to
mapping fixed function pipelines to shaders, or attempting the tackle
the task of shader composition, this will mean that users will have to
build a scene graph with osg::StateSet/osg::Program/osg::Uniform
specifically for the OpenGL ES 2.0 target. In the past we've often
discussed OpenGL 3.0 port in terms of how to do we handle the fixed
function pipeline mapping and implementation shader composition, and
this is something I still see as a long term goal, however, it's way
to ambitious to be able to implement within the time constraints and
without significant changes to the OpenSceneGraph. So I'm keeping my
goals humble, and milestones within reach and by doing so make them
the goal obtainable.
Another key aspect of what I want to achieve is open the door for
OpenGL ES 1.1 and OpenGL 3.x support with a modest amount of
additional effort above the OpenGL ES 2.0 port. I don't have the time
or resources to tackle the port to these targets myself within the
next few months, but I believe it should be possible to facilitate
support for these targets with the appropriate approach to adding
support to OpenGL ES 2.0, and given assistance of the community we may
well be able to add support for these additional targets at the same
time or shortly after the introduction of OpenGL ES 2.0 support. In
fact I'm actually optimistic that the similarity between OpenGL ES
2.0, OpenGL 3.x w.r.t focus of shaders, and even OpenGL 2.x (if you
ignore the fixed function pipeline) will enable us to test out OpenGL
ES 2.0/OpenGL 3.0 style code paths even with out having one or both
installed. If we get it right we may enable contributors working on
OpenGL 2.x or OpenGL 3.x be able to help out the OpenGL ES 2.x port,
and visa-versa.
I won't delve too much into the implementation details right now, as I
just have some preliminary designs down on paper and in my head, I
really need to test a couple of different strategies out before I
start committing to a specific approach. My intention is to settle on
the final approach to OpenGL ES 2.0/OpenGL 3.x and OpenGL ES 1.1 in
the next week or two, and will keep the community informed of
progress.
If you've already done your own porting work to either OpenGL ES 1.1,
OpenGL ES 2.0 or OpenGL 3.x then please come forward with details, and
ideally post some code and pass on what you've learned from the work
so that we can roll this into what will finally make it into
svn/trunk.
Thanks in advance for you support, patience and wisdom,
Robert.
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