[Bug 88506] GL_ARB_texture_float is half float only

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Jan 20 13:42:34 PST 2015


Ian Romanick <idr at freedesktop.org> changed:

           What    |Removed                     |Added
             Status|NEW                         |NEEDINFO

--- Comment #3 from Ian Romanick <idr at freedesktop.org> ---
(In reply to kaillasse91 from comment #2)
> I just found this old bug report :
> https://bugs.freedesktop.org/show_bug.cgi?id=44039

Oh.  Yeah, that's the problem.  Like I mentioned in one of the comments on that
bug, "the problem is that GEN4 can't do filtering on 32-bit float formats." 
Your GM45 is GEN4.  We could either not support floating point textures at all,
or we can give 16-bit formats when the application asks for GL_RGBA32F.  It's
one of those "all solutions are bad" situations.

> Is it not related to what I've found (silently fallback to 16 bits format
> when 32 bits asked) ?
> OpenGL vendor string: Intel Open Source Technology Center
> OpenGL renderer string: Mesa DRI Mobile IntelĀ® GM45 Express Chipset 
> OpenGL version string: 2.1 Mesa 10.5.0-devel (git-461103e 2015-01-18
> trusty-oibaf-ppa)
> OpenGL shading language version string: 1.20

(In reply to kaillasse91 from comment #0)
> My problem is that it does it silently instead of telling me that this
> format is unsupported so I can choose what to do.

I think if you query GL_TEXTURE_RED_SIZE it will tell you the number of bits
actually used by the implementation.  Skimming Mesa code, I'm pretty sure it
will return 16 if GL_RGBA16F was used and 32 if GL_RGBA32F was used.

Can you try that?

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