>> The fourth extension, ARB_shading_language_100, is not (yet) exported
>> by any renderers.
>To really show my ignorance, why do I need this 4th if I already have
>the first three. I need to check but I don't think the PC where we
>have our shaders working has this language symbol defined.
Because the specification requires it. Any and all documentation on GLSL
will tell you that to determine if the shading language is available you
must check for ARB_shading_language_100. Drivers will often expose entry
points for "experimental" and "beta" development. Yes, you can poke around
and find the entry points, but you are essentially "hacking" into the
preliminary GLSL support in OS X. The above mechanism is how a vendor
advertises that it is "ready" for use in applications.
ATI and NVIDIA PC drivers currently do in fact expose this token and GLSL
works on the PC. I am a little disappointed by Apple's slowness in this
regard. My guess is that they are waiting for Tiger so that OpenGL 2.0/SL
support can be one more reason to upgrade.
That the entry points are there is "interesting"... I imagine there is
probably a way to enable the shading language, but those who know are
prevented by NDA from disclosing it or discussing it. I also wonder if it's
simply so that the entry points exist so that if Tiger based apps are run on
the older OS X, the apps will still load (entry points match up... I'm still
a little new to the Mac, but I'm imagining it's something akin to having DLL
entry points available, or the app won't load on the PC).
Richard S. Wright Jr.
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