[osg-users] problem with HDR, values clamped?

Art Tevs stud_info2 at yahoo.de
Fri Sep 21 03:26:01 PDT 2007


Hi, Benoit.

Yes there is a kind of clamp. 16 Bit float values can
only represent values upto 65504. Thus it is a good
practice to add something like:

color = min(color, 65504);

At the end of your shaders.

See nVidia's FP_Specials.pdf for more info.


Cheers, Art


--- Benoit bossavit <bnuaster at gmail.com> schrieb:

> Hi all,
> 
> I'm trying to do a render in HDR with a CameraNode
> (osg1.2).
> I have a texture where I set an Image wich contains
> float values :
> 
>     img->setImage( width, height, 1,
> GL_INTENSITY16F_ARB, GL_LUMINANCE,
> GL_FLOAT, data, osg::Image::USE_NEW_DELETE );
>     texture->setImage(img.get());
>     texture->setFilter( osg::Texture::MIN_FILTER,
> osg::Texture::LINEAR );
>     texture->setFilter( osg::Texture::MAG_FILTER,
> osg::Texture::LINEAR );
>     texture->setWrap( osg::Texture::WRAP_S,
> osg::Texture::CLAMP );
>     texture->setWrap( osg::Texture::WRAP_T,
> osg::Texture::CLAMP );
> 
> 
> In data I put values between 0.0 and 70000.0
> I give this texture to my shaders and I project it
> with glsl function
> texture2DProj().
> I have an artefact with the render (after tone
> mapping). Values upper than
> 65510 (not 65536) seems wrong.
> It's possible there is a max for float value with
> texture 16 bits ? and
> these max is "the same" that integer value? the rest
> of values or good, I
> can obtain for exemple a value like 25630.56.
> 
> Someone can see something?
> 
> thanks you.
> 
> bnua
> > _______________________________________________
> osg-users mailing list
> osg-users at lists.openscenegraph.org
>
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
> 



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