[osg-users] OpenGL 3.1 at GDC

Paul Martz pmartz at skew-matrix.com
Wed Mar 25 08:46:57 PDT 2009


Sorry. I didn't think I needed to explain this, I mistakenly thought
everyone knew it. Take your example of a DX3 app running on a DX10
implementation. The DX3 app gets nothing other than the DX3 API. Should the
software developer attempt to use just one new feature in DX10, the only
route forward is to port the _entire_ app to the new DX10 API.

Compare this to OpenGL. An OpenGL 1.0 app running on an OpenGL 2.1
implementation has access to all the features that have been added in each
successive release, and you can modify the app to access those features
without porting your entire app.

Only in OpenGL 3.1 does this model change, but now you have a couple choices
as an app developer:
 * Don't modify context creation. You continue to get a 2.1 context, but you
also have access to many new 3.x features available as ARB extensions.
 * Create a 3.0 context, or a 3.1 context with the compatibility extension.
You get essentially the same results as with 2.1, except the same new
features you had access to as ARB extensions are now core features, and
there are additional new ARB features available.

You'll eventually port away from 1.x/2.x, but this system allows you to do
so on your timetable, not someone else's.

That is the compatibility difference between the two APIs in a nutshell.

Paul Martz
Skew Matrix Software LLC
http://www.skew-matrix.com
+1 303 859 9466

-----Original Message-----
From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Tueller,
Shayne R Civ USAF AFMC 519 SMXS/MXDEC
Sent: Wednesday, March 25, 2009 9:09 AM
To: OpenSceneGraph Users
Subject: Re: [osg-users] OpenGL 3.1 at GDC

Paul,

In what way has D3D screwed the existing user base with each new release?
I'm not trying to argue your point, I just want to understand where you're
coming from here.

-Shayne

-----Original Message-----
From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Paul Martz
Sent: Wednesday, March 25, 2009 8:31 AM
To: 'OpenSceneGraph Users'
Subject: Re: [osg-users] OpenGL 3.1 at GDC

> YES!!!!!!!!!!!! :)))))))))))))))
> 
> but robert, thanks for your arguments! i will use them there. ;)
> 
> best regards to all and other arguments are welcome too!

I agree with Robert's sentiment. In many ways, D3D has chosen the easy way
out -- supporting only one platform, and screwing the existing user base
with each new release. This is the easy way to develop an API. Running cross
platform, continuing to evolve and remain relevant, and not screwing
existing users is a much harder task, but OpenGL has a proven track record
of success in all these areas.

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