Re: note on problem reports
Re: note on problem reports
- Subject: Re: note on problem reports
- From: Paul Schneider <email@hidden>
- Date: Tue, 22 Jul 2008 09:22:20 -0500
Hi Kristian,
Okay, but it seems that to provide consistent output for both Motion
and FCP, I'll have to premultiply in one host but not the other. Can
you confirm that this is the normal way to do this? Also, since I
don't seem to get any information with which I can differentiate
between the two cases, except -hostIsMotion et al.
Both FCP and Motion expect premultiplied output from FxPlugs.
FCP will often convert your output back to straight to apply more
processing. Motion works premultiplied internally, so in a simple
test (one layer, just your generator in a timeline) it will just
display your color channels directly to the screen. But you will
still see problems when Motion starts using your alpha channel in more
interesting ways (adding a shape, or working with more layers).
Anyway, isn't half the point of making a generator instead of a
filter that I should simply include an alpha channel and leave it to
the host app to blend with lower layers?
The host composites your output with the layers below, whether you are
a filter or a generator (or a transition). But the rules for
compositing premultiplied images are different than those for
compositing straight images, as I'm sure you're aware.
One reason why many compositing applications prefer working
premultiplied is that the typical "over" operation is so much simpler;
compositing two premultiplied images can be done by simply adding the
color channels.
- Paul
On Jul 22, 2008, at 5:42 AM, Kristian Harms wrote:
Den 21. juli. 2008 kl. 18.32 skrev Darrin Cardani:
The third problem is only in Motion: If an FxPlug effect generates
pixels that are fully transparent, but have the R, G and B
channels set to some non-zero value (e.g. 127 if we're talking
UInt8), then Motion won't treat these pixels as fully transparent,
but will instead show any underlying layer as "washed out", and
the black default background will shine through as grey. This is
with the normal blending modes. (Apple guys, the problem ID is
#6079465.)
As Steve mentioned, this is a problem on your end (and you're not
the first person to have this problem). You just need to
premultiply your pixel values, and everything will work as expected.
Okay, but it seems that to provide consistent output for both Motion
and FCP, I'll have to premultiply in one host but not the other. Can
you confirm that this is the normal way to do this? Also, since I
don't seem to get any information with which I can differentiate
between the two cases, except -hostIsMotion et al.
Anyway, isn't half the point of making a generator instead of a
filter that I should simply include an alpha channel and leave it to
the host app to blend with lower layers?
Thanks for your answers, both Steve and you :-)
-- Kristian Harms
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Pro-apps-dev mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Pro-apps-dev mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden