"Rune" <run### [at] inamecom> wrote in message
news:39d4a5b8@news.povray.org...
|
| When the output-colour is calculated, the background should be ignored in
| the output-colour, and only be stored in the output-alpha. Currently the
| background is stored in both.
|
| But then a new question arises - exactly *how* should the background be
| stored in the alpha channel? How should it be calculated?
<snip>
| I think that POV-Ray, when the alpha channel is turned on, should convert
| all kinds of transparency into the kind that can be stored in the alpha
| channel. I know that it will not work 100% correct, but it's the only
option
| if we want to be able to use effects such as media together with the alpha
| channel.
|
| The good news is that there's a simple way to convert any kind of
| transparency into the percentage kind of type that can be stored in the
| alpha channel. The method is a very general one. For the percentage type
of
| transparency it will be calculated completely accurate. For other types of
| transparency it will convert it in a somewhat meaningful way.

How is it done in computer games?
Not something I know about but I can see the reasoning behind this
discussion.  If the alpha channel affected antialiased edges of objects in a
way that the edges were treated as semi-transparent when loaded into a post
processing program then no matter what background the image were pasted over
it would mix with it correctly.
That seems a lot different than what you are suggesting, but maybe because I
don't know what it is exactly.  Well, I am following it somewhat anyway.
The root of the matter still seems to be about the discontinuity at the
rudimentary level of alpha channeling, so you're saying to fill that void
with a purposeful color with the intent of doing the already possible
transparency info method in place of the plain background which always is an
inclusion anyhow except it's unavoidable.  And you think a proxy background
could be applied in the source to do a post process sort of thing.  Sorry if
I'm wrong in my interpretation, just trying to describe what I think you
mean.
Well, I don't understand how gray is any better than it being black or any
other color  :-)
My thoughts go toward the need for a self-color blending, which I think has
been mentioned before.  However that would be done... but to my point about
this: isn't some form of transparency already done in other things such as
game graphics, paint programs, etc?  I know that in PSP it's a simple thing
to use a semitransparent image and paste it onto another image but there
never is a implied background color beforehand.
Please excuse me for being late on the talk BTW, and for half listening in
on it until now.

Bob

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