[Bf-committers] Color pipeline todo: alpha

[Ton Roosendaal]

Hi,

I honestly can't guess which of the associations would be which alpha or color. 
This will lead to a lot of confused people.

-Ton-

------------------------------------------------------------------------
Ton Roosendaal  Blender Foundation   ton at blender.org    www.blender.org
Blender Institute   Entrepotdok 57A  1018AD Amsterdam   The Netherlands

On 20 Dec, 2012, at 20:52, Brecht Van Lommel wrote:

> I like the names associated and unassociated because they don't
> describe how you arrived at the color, just the way it is stored. For
> rendering you don't premultiply things, it just comes out that way
> naturally. Though perhaps the terms premultiplied/unpremultiplied are
> more familiar to users.
> 
> Brecht.
> 
> On Thu, Dec 20, 2012 at 8:33 PM, Ton Roosendaal <ton at blender.org> wrote:
>> Hi,
>> 
>> The convention is probably based on where the graphics comes from.
>> 
>> - Straight alpha:
>> Painted graphics and exporting it with an alpha mask. Colors remain unchanged.
>> 
>> - Unpremultiplied color:
>> Images from render and composite, converted to display color.
>> 
>> - Premultiplied color:
>> A straight alpha image, converted to to premultiplied colors.
>> 
>> Each is actually different :)
>> 
>> -Ton-
>> 
>> ------------------------------------------------------------------------
>> Ton Roosendaal  Blender Foundation   ton at blender.org    www.blender.org
>> Blender Institute   Entrepotdok 57A  1018AD Amsterdam   The Netherlands
>> 
>> On 20 Dec, 2012, at 20:20, Troy Sobotka wrote:
>> 
>>> On Thu, Dec 20, 2012 at 10:36 AM, Brecht Van Lommel
>>> <brechtvanlommel at pandora.be> wrote:
>>>> Premul for float and key for byte images could work.
>>> 
>>> Just in the interest of consistency, if we are going with
>>> "Premultiplied" naming convention, can we roll with the inverse of
>>> "Unpremultiplied" and apply it consistently?
>>> 
>>> I checked in with Mr. Selan and he suggested that "Unpremultiplied" as
>>> consistent. Mr. Gritz uses[1] the TIFF convention of "Associated" and
>>> "Unassociated" convention.
>>> 
>>> I'm open to whatever naming convention we rest on, and only hope we
>>> can apply it consistently throughout the interface. In particular, the
>>> sidebar panels should likely list "Premultiplied" and the node
>>> conversion should reference "Premultiplied" and "Unpremultiplied."[2]
>>> 
>>> The "Color Unpremultiply" term should probably be re-evaluated to
>>> avoid confusion, as it is an order of operations event, and the
>>> current label is far to close to the other terms which can only amount
>>> to greater confusion.
>>> 
>>> Blender needs to take whatever path is most healthy for it, but we can
>>> at least aim to apply the terminology consistently.
>>> 
>>> With respect,
>>> TJS
>>> 
>>> [1] http://lists.openimageio.org/pipermail/oiio-dev-openimageio.org/2011-April/004193.html
>>> [2] http://comments.gmane.org/gmane.comp.lib.openimageio.devel/1406
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