[Ross Newton]

Yes, I want to be able to “select” an alpha channel.. And there’s layer effects to do this (“Set Channels, Set Matte, etc.) But you realize this wouldn’t be at the codec or render level… you would set it up in the comp and then just render as “RGB + Alpha” to whatever filetype you want, same as any other render and filetype that can handle the extra alpha channel.

It’s just like any other render with an alpha, it’s just this alpha wouldn’t equal transparency. The alpha channel is just another channel, it doesn’t have to equal transparency, but it seems like AE forces this at the comp level.

I even played around with some of the channel effects like “Set Channels” and “Set Matte”. No matter what, it always mattes the alpha through to the background color set for the comp. I was hoping there was a setting to turn this off. You see if it didn’t do this, then I’d have my building, my sky, and my alpha channel. As it is now, the alpha knocks out my sky and renders through to the AE background color, which is set to black.

[Ross Newton]

Thanks again for the response Dave.

Actually, I think you’re misunderstanding what I’m asking. I know how to render an alpha channel that represents the transparency of my comp using the appropriate render settings.

What I’m trying to do is render an alpha channel with my comp, that DOESN’T represent any transparency and therefor doesn’t get matted in my comp and in the render. I want to “override” the alpha channel with what I choose.

In the above example, I have a CG building and “solid” sky in my comp, so in AE’s world I have no alpha channel because it’s completley blocked by the full-frame “solid-based” sky. HOWEVER, I want the CG building’s alpha to “override” the alpha for my comp when I render it out. The PROBLEM is that, whenever I do a set channels or set matte on my comp, it always MATTES that alpha channel thus killing my sky layer and matting it to the background of the comp.

What I want is a FULL RGB render of my building and sky WITH the alpha channel set as the building’s alpha channel… all in ONE render (yes, I know I can do it seperately). The reason I posted this is to see if I can do it in one render. Other compositing packages can do this with no problem, they don’t automatically matte your comps based on your alpha channel.

Now, you’re probably wondering, why would I want to do this if I’m already in the comping process. In this case, I’m actually building sub-comp passes for a senior compositor who wants to bring in the building, sky, and then use the CG building’s alpha as a color-correction matte for the building. It just makes it easier if I can do all that in one pass.

That’s the crux of my questions… can AE do this?

[Ross Newton]

Hi Dave, thanks for the response.

I think you answered my question, that unless there’s transparency in the comp, then there’s no alpha. That’s what I’m trying to basically do, add an alpha channel but not use it for transparency upon rendering out.

I know I can duplicate the comp and just render an alpha out of the building. I was trying to avoid that just to save time and see if this could be done, like other compositing programs.

It’s basically like a shortcut for the compositor, even though we want the sky in the RGB of the shot, I wanted to include the building’s alpha channel as a way of isolating the building, and to do this quickly in AE.

[Ross Newton]

My memory is a little fuzzy because it’s been a while.

But for layers where I needed my original track scaled up by 100% (that I’m sure I painfully hand-keyed) I had to parent that layer with the track to a new solid. I then scaled the solid up 100% (this scales the track up). Then I unparented from the solid. I then had to bring in my new 2K VFX element and parent that to the original layer that scaled up. The new 2K VFX layer now had the appropriately scaled up track.

For layers where I needed masks, I did the same thing as above. Scaled them up by parenting them to a solid. Then I used the “Fill” effect to fill in the masks with white and filled the rest in with black (by using a new black solid and copying the masks and effects over to it). I had to bring in my 2K VFX elements and use a track matte (set to luma) and this made the masks work as they originally did on the new 2K VFX elements.

It was a nightmare, but I got it all working in the end. Lesson learned: use proxies!

[Ross Newton]

Awesome! It worked for me first try. The only catch I found was that the last keyframe can’t be on Easy Ease. It had to be linear to work for me.

This same code also works in Flash too. It’s like the universal springiness equation.

[Ross Newton]

Good Call!!! This little option was causing all kinds of problems in my final render of my demo reel. Thanks for posting this tip. Now everything doesn’t look all aliased and jaggy!

[Ross Newton]

I had the same question and just found a script at the following forum site:

https://www.aenhancers.com/viewtopic.php?f=3&t=991&p=3833#p3833

It seems to work! Good luck.

[Ross Newton]

I think my issue is that I should have been using the normal proxy workflow.

I should have knocked all my plates down to half size, setup proxies, and then setup all my composites and 3D elements.

Then I could have just replaced the proxy with the normal footage and rendered out.

[Ross Newton]

Awesome help! Thanks.

Ross

[Ross Newton]

Anyone? I’m still stuck on this and I think it would be a common issue.

Thanks – Ross