[opensource-dev] Review Request: VWR-24420: PNG images which specify "background color" lose alpha layer when imported.

Joshua Bell josh at lindenlab.com
Mon Jan 10 10:57:56 PST 2011


On Mon, Jan 10, 2011 at 8:34 AM, Ponzu <lee.ponzu at gmail.com> wrote:

> A common cause of z-buffer problems in SL is textures that do not *need* an
> alpha channel that contain one anyway.  Lots of content in SL is created by
> rank amateurs (me for example).
>
>
That seems like a good point, and might explain the existence of the code
(although I'm just responding to the thread here, not as a domain expert).


> What if the upload dialog had a check box?
>
>     [ ] This texture should have an alpha channel.
>
> If the box is not checked, the alpha channel is removed.  If it is checked,
> it is retained, unless it is not there, in which case the user gets an error
> message.
>
>
Without digging more deeply into the issue, but putting on my UI design hat,
if it's necessary to ask the user I'd suggest the wording:

[x] Preserve transparency (alpha channel)

The wording "This texture should have an alpha channel" seems like it could
lead to users thinking "hey, sure, why not, sounds like a good idea" and
checking it.

If the image does not have an alpha channel, remove or disable the checkbox
from the UI.

Then there's the question of whether or not the box should be checked by
default or not. Ponzu's point is compelling that the current behavior is
implicitly desired by many content creators to avoid problems ("I uploaded a
new texture and it's rendering differently than the textures I uploaded last
week! SL sucks!"). Which would mean that this could default to unchecked
(i.e. current behavior) but be exposed for users who know what's going on
and would let them toggle it live with the preview.

(Again, just speculating here as well, I haven't dug into the code.)

-- Josh
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