Re: [Openexr-devel] Shade me confused

[Drew Hess]

It's already there.  If you look in glext.h in the Nvidia Cg SDK, you'll 
find this:

#define GL_HALF_FLOAT_NV                  0x140B

So if you have a half framebuffer, all you really need to do is change the
input pixel type to GL_HALF_FLOAT_NV in the glTexImage2D call (once the
bug is fixed) and it should work.

We use half to represent color channels and float for things like Z,
normals, etc.


-dwh-



 On Thu, 27 Mar 2003, Nafees Bin Zafar wrote:

> Are there plans for a GL_HALF_NV type?  I would thing it would be at 
> least equally natural for the main program to do the conversion to half, 
> and explicitly specify that it's sending in half format data.  Also it 
> is plausible to imagine that an application's internal format is half, 
> in which case there would have to be a convert to float, only for a 
> convert back to half to occur right away in the driver.
> 
> Or am I missing something?  Is comptime's internal format half, or 
> float?  Nuke uses floats.
> 
> -n
> 
> Drew Hess wrote:
> 
> >It is float data that gets uploaded to the card, due to a bug in the 
> >current (as of 4290) Nvidia drivers.  Once the bug is fixed, we'll be able 
> >to send half data to the card instead.  It may be fixed in today's 4390 
> >drivers on Windows, but I'm waiting for the equivalent Linux drivers to 
> >find out.
> >
> >The magic conversion happens in the glTexImage2D call (the GL_FLOAT 
> >parameter specifies the input pixel type).
> >
> >
> >-dwh-
> >
> >
> > On Thu, 27 Mar 2003, Nafees Bin Zafar wrote:
> >
> >  
> >
> >>Hi Drew.  Looking through the ImageViewFragShader class, I see that the 
> >>texel data passed into glTexImage2D() is just regular float data.  The 
> >>internal format spec is set to GL_FLOAT_RGBA16_NV.  So where does the 
> >>magic conversion to half type occur?
> >>
> >>I am hoping that float data doesn't get transferred to the graphics card 
> >>because that would transfer 16 unnecessary bits.
> >>
> >>-n
> >>
> >>
> >>    
> >>
> >
> >
> >
> >
> >  
> >
> 
> 
>