View Full Version : Generating Preview with alpha - broken or me?

08-18-2007, 11:54 AM
Hello all,

In previous versions of LW when I generated a preview it contained an Alpha channel by default. Now in 9.2 when I'm doing the same thing it seems to not do it anymore.

Does anyone know if there is a setting for this that I'm missing? I'm saving out to Quicktime Animation with millions+, AE shows that it has an alpha, but it's all white, not correctly masking anything.



08-20-2007, 09:56 AM
Only two settings I know of that affect alpha are 1 Surface Editor>Advanced>Alpha Channel Tab which is usually set to 'surface opacity' to work right and 2 Object Propeties>Render>Alpha Channel Tab which is usually set to 'Use surface Settings'. Try changing either to Constant Value or Unaffected by Surface, for what its worth I'm using the 9.3 UB and having no problems with alphas

08-20-2007, 11:06 AM
Just to clarify, I'm not talking about the renderer, I'm talking about making a viewport preview. Viewport previews used to have an embedded alpha and the background used to drop right out in a compositing app.

thanks for the reply, though.

08-20-2007, 11:51 AM
I never noticed that!
Can you make the background black and comp it that way?

08-21-2007, 08:30 AM
I didn't even think you could take the viewport previews into a different app. I thought those would only work in LW.

08-21-2007, 01:12 PM
yes you can hit "save preview" and save out your preview file to an AVI or a quicktime depending on which settings you used to make your preview.

It WAS a very useful feature, but ARGH!

I used the black bckground with unmult in AE, but that isn't ideal.

08-21-2007, 01:29 PM
I've never gotten an alpha channel in a preview in either 8.5 or 9.2. Tried both saving as Quicktime and as .avi file. When dropped into After Effects and hit Ctrl+F (interpret footage) no alpha is present.

Does the appearance of your viewport matter as to whether or not an alpha is created? I leave grid lines on in my camera's viewport.

08-21-2007, 02:03 PM
I've saved the preview out to an AVI but couldn't get anything else to open it. Granted I probably didn't try very hard.

08-21-2007, 02:21 PM
hmm... maybe this was a mac thing... I used to do it mostly on the mac and now I'm PC. I think I'm going to try on my wife's powerbook. will check back with results.


08-21-2007, 02:43 PM
It's a mac thing. The mac LW doesn't have any preview options, it just makes the preview... with an alpha channel... the way I want it. The PC just won't do it no matter what the settings you chose (and there are a lot of them).

so, all you whiney mac users can be happy that you have a feature PC users don't. :)

see attached for proof.


08-21-2007, 11:45 PM
Funny, <whine>we used to have preview options!:cry:</whine>
For a few versions anyway - maybe they're somewhere else? I remember swithcing from Animation (default, has an alpha) to something else