add_layer {alpha alpha.red alpha.beta}
nice
On 17 February 2013 13:55, Ivan Busquets <[email protected]> wrote:
> 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
>>>>
>>>> _______________________________________________
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>>>>
>>>
>>>
>>
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>
>
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