Re: [Openexr-devel] luts

[Ken McGaugh]

Lutz Latta wrote:
> Sorry, I was wrong. I overlooked the fact that the value that is split 
> up is not used as integer, but as floating point with mantissa and 
> exponent. My suggestion only works for integer values like [0..65535].
>
> I'm afraid that there are probably no easy alternatives to make those 
> kind of bit manipulations in ARB_fragment_program. You could try to 
> decode the half value into mantissa and exponent by doing all kinds of 
> multiplication or other operations, driving it close to its numerical 
> limits. But considering that other hardware doesn't offer true half 
> operations, this is unlikely to be portable - if it is possible at all.
>
> Sorry,
>  Lutz

Thanks anyway.  I'm trying to get a 1D texture working as a lut right
now instead.

BTW, I have successfully used half data on other hardware, namely my
G4 powerbook with an ATI graphics card.  It runs so fast I have to
assume it fully supported in the ATI hardware.

--Ken