[Bf-committers] Color to greyscale conversion - confusion

[Campbell Barton]

On Mon, Jun 25, 2012 at 10:44 AM, Knapp <magick.crow at gmail.com> wrote:
> On Mon, Jun 25, 2012 at 10:19 AM, Campbell Barton <ideasman42 at gmail.com> wrote:
>> On Sat, Jun 23, 2012 at 7:39 PM, Troy Sobotka <troy.sobotka at gmail.com> wrote:
>>> On Jun 23, 2012 5:01 AM, "Campbell Barton" <ideasman42 at gmail.com> wrote:
>>>
>>>>
>>>> - Texture and shading pipeline use rgb_to_bw() which treat RGB more
>>>> evenly which might be better for shading when very un-even influences
>>>> for RGB channels could be problematic for shading with textures of
>>>> different colors (rgb_to_bw)
>>>>
>>>> - Where as with compositing - perceptual rgb->bw is much more
>>>> important (rgb_to_grayscale)
>>> g list
>>>
>>> Technically this is in the domain of LUTs once OCIO lands.
>>>
>>> The problem with attempting a non color aware approach is that it takes us
>>> directly into the hard coded color domain again, as all values are assumed
>>> 1:1 linear sRGB.
>>>
>>> With respect,
>>> TJS
>>
>> Don't think lack of OCIO is an excuse for arbitrary/different hard
>> coded conversions in our code.
>> Will add comments to these functions to say we don't know why they are
>> different and someone who has a clue could clear up the confusion one
>> of these days :S
>
> That makes no sense to me. When is this person going to show up? What
> makes you think he will ever come? Best to find the answer now and not
> incur any more debt.

That was the purpose of this thread, since nobody knows - we better at
least document that this is a mystery so anyone reading the code is
aware,
this doesn't incur technical debt - it just exposes it.

See:
http://projects.blender.org/scm/viewvc.php/trunk/blender/source/blender/blenlib/intern/math_color_inline.c?root=bf-blender&r1=48259&r2=48258&pathrev=48259

-- 
- Campbell