I'm not sure that Posterize would give the desired result in this case,
since it will still throw values that are not possible to represent as a
half precision float.
You'd probably want to re-create a 16 bit half-float value by breaking the
32 bit float into its exponent and mantissa(significant) values, and then
truncating those.
The following expression might work (not thoroughly tested, though)
set cut_paste_input [stack 0]
version 7.0 v4
push $cut_paste_input
add_layer {alpha alpha.red alpha.beta}
Expression {
expr0 "exponent(r) > 16 ? r*inf: ldexp(rint(mantissa(r)* (2**11))/(2**11),
exponent(r))"
expr1 "exponent(g) > 16 ? g*inf: ldexp(rint(mantissa(g)* (2**11))/(2**11),
exponent(g))"
expr2 "exponent(b) > 16 ? b*inf: ldexp(rint(mantissa(b)* (2**11))/(2**11),
exponent(b))"
channel3 alpha
name Float_To_Half
selected true
xpos 292
ypos 226
}
Hope that helps.
PS. Mark, hope you're doing well! :)
On Sun, Feb 17, 2013 at 5:35 AM, Shailendra Pandey <[email protected]>wrote:
> well actually 281474976710656 -1
> 281474976710655
> Hope that helps
>
>
>
> On Sun, Feb 17, 2013 at 9:25 PM, Shailendra Pandey <[email protected]>wrote:
>
>> Hi Mark
>>
>> You can use a posterize node
>> with a value of 281474976710656
>> which is 2 to the power(16*3)
>>
>>
>>
>> Cheers
>> Shail
>>
>> On Sun, Feb 17, 2013 at 6:25 AM, Mark Nettleton <[email protected]>wrote:
>>
>>> **
>>> I'm generating an ST map within Nuke, that needs to line up with 16 bit
>>> half float ST map images on disk.
>>>
>>> Is there a way I can generate 16bit half float values within nuke? Or
>>> convert 32 bit values to 16 bit half? (without writing to disk and reading
>>> back)
>>>
>>> Thanks
>>>
>>> _______________________________________________
>>> Nuke-users mailing list
>>> [email protected], http://forums.thefoundry.co.uk/
>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
>>>
>>
>>
>
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