Mads:
When you say we changed it, did we at one time have a merge2 node that did
not clamp and we changed the formula on the Merge2 node to then clamp?
I suspect this predates The Foundry's involvement in Nuke (Merge2 node was
introduced before 2007) and anyone who did make the modification has long
since left. I looked through our bug database and no one has filed a bug
though I did find a previous post on this list asking the same question
back in 2012. The trouble is if no one emails support and files a bug then
it does not exist as a feature request/bug.
Nuke-Users is not an official Foundry channel for filing bugs/features, it
is just a channel for like minded users to converse with each other. You
should send this into supp...@thefoundry.co.uk and get this logged.
--
Deke Kincaid
Media & Entertainment OEM Development Manager
The Foundry
Skype: dekekincaid
Tel: (310) 399 4555 - Mobile: (310) 883 4313
Web: www.thefoundry.co.uk
Email: d...@thefoundry.co.uk
On Wed, Jan 28, 2015 at 9:31 AM, Mads Lund <madshl...@gmail.com> wrote:
> But i guess that leads back to the original question.
> I can't find a single reason (artistically or technically) why they
> changed this to clamp between 0-1.
>
> On Wed, Jan 28, 2015 at 6:03 PM, Ivan Busquets <ivanbusqu...@gmail.com>
> wrote:
>
>> For more crude / unclamped versions of some merging operations (including
>> "overlay"), you can also use the olde "Merge" node (as opposed to the
>> default "Merge2".
>>
>> Merge {
>> inputs 2
>> operation overlay
>> name Merge1
>> selected true
>> xpos -254
>> ypos 199
>> }
>>
>>
>> On Wed, Jan 28, 2015 at 8:34 AM, Mads Hagbarth Lund <madshl...@gmail.com>
>> wrote:
>>
>>> It's just bad with the overlay thing, as it is a pretty useful way to
>>> add grain and do dodge/burn effects. It works out of the box in Photoshop,
>>> Fusion and AfterEffects but you have to make your own overlay gizmo to make
>>> it work in Nuke.
>>>
>>>
>>> Den 28/01/2015 kl. 17.11 skrev Daniel Short <danisnotsh...@gmail.com>:
>>>
>>> I wondered how the screen would need to be calculated differently since
>>> the invert function might get you some crazy values in float space.
>>> It makes sense that they changed it to give us a visually accurate
>>> result when a mathematical one would look like an error.
>>>
>>> On Wed, Jan 28, 2015 at 10:49 AM, John Mangia <j...@johnmangia.com>
>>> wrote:
>>>
>>>> Looks like the nuke screen algorithm has a low pass to allow for values
>>>> over 1 to comp more naturally. You can see the difference if you expose
>>>> down.
>>>>
>>>> On Wed, Jan 28, 2015 at 10:37 AM, Mads Lund <madshl...@gmail.com>
>>>> wrote:
>>>>
>>>>> Ahh ok, so the "Screen" operation in the merge node does not just
>>>>> screen.
>>>>>
>>>>> Screen is the same as the Merge
>>>>> <http://help.thefoundry.co.uk/nuke/9.0/content/reference_guide/merge_nodes/merge.html>
>>>>> node,
>>>>> only with operation set to screen by default. It layers images
>>>>> together using the screen compositing algorithm: A+B-AB if A or B ≤1,
>>>>> otherwise max(A,B). In other words, If A or B is less than or equal
>>>>> to 1, the screen algorithm is used, otherwise max is chosen. Screen
>>>>> resembles plus. It can be useful for combining mattes and adding
>>>>> laser beams.
>>>>>
>>>>> However i still don't see why they don't apply this to the overlay
>>>>> method aswell. (why would you want clamp the image?)
>>>>> And it also doesnt explain why it clamps at 0 (since multiply does not
>>>>> clamp at 0)
>>>>>
>>>>>
>>>>>
>>>>> On Wed, Jan 28, 2015 at 2:46 PM, John Mangia <j...@johnmangia.com>
>>>>> wrote:
>>>>>
>>>>>> Screen is also a multiplicative operation, it's just inverted images
>>>>>> multiplied together and re-inverted.
>>>>>>
>>>>>>
>>>>>> On Wed, Jan 28, 2015 at 8:35 AM, Ron Ganbar <ron...@gmail.com> wrote:
>>>>>>
>>>>>>> The math used in Nuke for Screen makes it inheritingly clamp (it
>>>>>>> doesn't really clamp, but can not produce colors brighter than 1).
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Ron Ganbar
>>>>>>> email: ron...@gmail.com
>>>>>>> tel: +44 (0)7968 007 309 [UK]
>>>>>>> +972 (0)54 255 9765 [Israel]
>>>>>>> url: http://ronganbar.wordpress.com/
>>>>>>>
>>>>>>> On Wed, Jan 28, 2015 at 2:15 PM, Mads Lund <madshl...@gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> According to the documentation:
>>>>>>>>
>>>>>>>> • overlay - Image A brightens image B.
>>>>>>>> Algorithm: multiply if B<.5, screen if B>.5
>>>>>>>>
>>>>>>>> However Nuke also clamps the colors between 0 and 1.
>>>>>>>> It seem that all other compositing software does not clamp between
>>>>>>>> 0 and 1, so i am wondering if this is a bug in Nuke?
>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
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>>>>>>>> Nuke-users@support.thefoundry.co.uk,
>>>>>>>> http://forums.thefoundry.co.uk/
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>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>>
>>>>>>
>>>>>>
>>>>>>
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>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>
>>>>
>>>>
>>>> --
>>>> John Mangia
>>>>
>>>> 908.616.1796
>>>> j...@johnmangia.com
>>>>
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>>>
>>>
>>>
>>> --
>>> Daniel Short
>>> www.danisnotshort.com <http://www.vimeo.com/danisnotshort>
>>> 215.859.3220
>>>
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>>
>>
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>
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