[osg-users] [osg-submissions] Fixed Function Pipeline to GLSL generator

Robert Osfield robert.osfield at gmail.com
Mon Mar 23 06:36:25 PDT 2009


Hi Maciej,

I'm replying to both osg-submissions + osg-users as ongoing general
discussion is likely.

On Mon, Mar 23, 2009 at 1:11 PM, Maciej Krol <mackrol at gmail.com> wrote:

> Glad to hear that You like it. I was suprised that it works for almost all
> scene state setups that I use. It would be quite simple to extend it with
> osgShadow support if we could only detect shadowing state of geometry.


osgShadow is mostly shaders already so I'm not sure it should be needed.
Where there specific parts you were thinking of?



> On WinXP NVidia Quadro NVS 320M I did not notice any performance drops.
> Maybe shaders are not properly cached?


It's not the GPU that was the issue, but the OSG's CPU overhead.  We're
talking about quite large models, 10' of thousands of obejcts so they tend
to be gated by CPU overhead anyway, so shaders just add more ovehead.  It
still got a solid 60Hz hertz though ;-)


> IMHO in OSG 3.0 state attributes and modes should be abstract - not tied to
> actual OpenGL implementation. High level attributes and modes could be
> mapped to different rendering implementation (GL 1.0; GL 2.0; GL 3.0; ESGL).
> This would be a major change, breaking compatibility with existing OSG
> application.


This pretty well what I have had in mind, this is the approach I was
advocating for OSG-3.0.


> Open discusion in osg-users is required. I am thinking about implementation
> for a long time, but my customers are not willing to pay for it. I could
> start implementation in my free time. It mainly depends on OSG 3.0 goals.
>

This type of general refactoring work is not so easy to sell - supporting
OpenGL 3.0 for instance is a worthy cause but it won't actually be a game
changer in terms of delivered features.  OpenGL ES is a different mattter
though, I believe this does offer real differences that could make a
difference to end user application delivery i.e. offer 3D apps in the
embedded space so might be more attractive to outside funding.  Ports to
consolses are also an area where perhaps funding might be possible in which
the general refactor work can fall out of it.

Without external funding we'll have to chip away at the task bit by bit.

Robert.
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