Alpha not clean (black BG, motion blur)

Become a member of the CGSociety

Connect, Share, and Learn with our Large Growing CG Art Community. It's Free!

Thread Tools Search this Thread Display Modes
Old 03 March 2013   #1
Alpha not clean (black BG, motion blur)


This is weird. I render my rotating object with the sky object invisible to the camera. That mean the render is on black background. However when I import it in After Effects and put the alpha setting at Premultiplied Black like it should be, I got a lot of mess around my object. Straight too of course. When I change the color to a dark grey, it get better on the edge but not on the motion blur.

Coming from Lightwave, I am use to perfect edges when using a black background.

Any way to fix that?

So long and thanks for all the fish
Old 03 March 2013   #2
Quote: I got a lot of mess around my object.

What do you mean? Aliasing problem?

Have you tried an object buffer for the same object and compared with the alpha? Is there a difference ?
Old 03 March 2013   #3
Did you set the Alpha channel in C4D as Premultiplied?
you do that by unchecking the "Straight Alpha" checkbox.
If you set your Alpha to Straight, C4D creates a "bleed" around the objects and the Alpha channel works perfectly, but you have to set AE to use Straight as well

It is better workflow to work in Straight Alpha, anyway.

Once again, PLEASE post an image or something.
A "mess" means nothing.
Old 03 March 2013   #4
Thanks Noseman, yes it was that. I forgot to update my post (rush rush job) but fixed it when I discovered (after googling a lot) the straight alpha switch. After that, the alpha was really clean.

Thanks a lot!!
So long and thanks for all the fish
Old 03 March 2013   #5
you are welcome...
Old 03 March 2013   #6
Thread automatically closed

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.
CGTalk Policy/Legalities
Note that as CGTalk Members, you agree to the terms and conditions of using this website.
Thread Closed share thread

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Society of Digital Artists

Powered by vBulletin
Copyright 2000 - 2006,
Jelsoft Enterprises Ltd.
Minimize Ads
Forum Jump

All times are GMT. The time now is 01:12 PM.

Powered by vBulletin
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.