alpha channel

dueyftw · Post by **dueyftw** » Mon Sep 22, 2008 11:18 am

I need to extract the alpha by it self. Anyway to do this? I thinking using masking?

Dale

Genete · Post by **Genete** » Mon Sep 22, 2008 11:32 am

Hi dueyftw,
what do you mean exactly by "extract the alpha by it self"? do you have a layer and want that other to be only shown where the first is alpha<100%?
It seems that the answer is masking but you have to be more precise.
-G

dueyftw · Post by **dueyftw** » Mon Sep 22, 2008 12:29 pm

I'm importing to Vue's alpha plan. I need the background to be pure black and the have the character punch through as an alpha. I can do this in gimp, at one frame at a time. I don't want to do it that way.

Any suggestions?

Dale

synthsin75 · Post by **synthsin75** » Mon Sep 22, 2008 1:58 pm

Masking should work, if I understand correctly. If you put your black background and your character into the same group (or bone) layer, with the character below the background. Set the group layer to 'reveal all', and the character layer to 'subtract from mask'.

slowtiger · Post by **slowtiger** » Mon Sep 22, 2008 2:01 pm

You could also export the scene normally as a PNG sequence with transparency, then use Gimp or Photoshop for a batch processing job to extract just the alpha channel from that.

dueyftw · Post by **dueyftw** » Mon Sep 22, 2008 2:07 pm

Thanks synthsin75.

Got to work.

Dale

synthsin75 · Post by **synthsin75** » Mon Sep 22, 2008 2:09 pm

Always glad to help out.

chucky · Post by **chucky** » Mon Sep 22, 2008 4:03 pm

you can also render mov's with alpha, so you may not need to have a mask.

synthsin75 · Post by **synthsin75** » Mon Sep 22, 2008 5:20 pm

I assume that's what he did Chucky. Just needed the mask to get the alpha in the right place.

dueyftw · Post by **dueyftw** » Tue Sep 23, 2008 7:15 pm

It turns out not only do I need the black outline, but the inside needs to be white, not alpha. Otherwise you get a ghost, not a solid figure. I add one more layer.

Dale

slowtiger · Post by **slowtiger** » Wed Sep 24, 2008 3:16 am

Uhm, you could easily extract that from the alpha channel as well in PS.

heyvern · Post by **heyvern** » Wed Sep 24, 2008 5:06 am

Wow. I was so confused about what was actually being done in this topic that I read a tutorial for importing avi into Vue. Good grief. It can't import video with an embedded alpha channel? You have to render it separately?

Are you sure about this? Isn't there a 32bit AVI format that includes the alpha? Then the "alpha" from AS would already be in there. Does Vue only work with two separate files, the image file and a separate alpha file?

Just curious. I have friends who think Vue is the cat's pajamas so this would surprise me a little. (I've never seen a cat wear pajamas so I couldn't be sure).

-vern

dueyftw · Post by **dueyftw** » Wed Sep 24, 2008 9:10 am

The problem with alpha planes is that the plane or it edges show up when rendering as being slightly darker in some 3d programs. It hard to get a clean alpha.

Dale

chucky · Post by **chucky** » Wed Sep 24, 2008 9:18 am

I have noticed that when importing a mov from AS to vegas you get an outliine if the alpha is set to premultiplied, if it is set to straight (unmatted) the alpha composites cleanly, I have wondered about the don't premultiply apha channel setting on the render. There is nothing in the manual about this.
Any thoughts?

Heyvern:
Wow. I was so confused about what was actually being done in this topic that I read a tutorial for importing avi into Vue. Good grief. It can't import video with an embedded alpha channel? You have to render it separately?

I guess it's like animation master, diffuse image map .. plus transparency image map. -A bit off that it isn't a bit more flexible.
I think I'm finally over Animation master BTW, I'm looking at switching to C4D, I know maya is the industry standard but it's boring and C4D is kindo' sexy, especially for a one man band.

It also happens to use vue as a plugin, nice.

heyvern · Post by **heyvern** » Wed Sep 24, 2008 12:34 pm

chucky wrote:
Heyvern:
Wow. I was so confused about what was actually being done in this topic that I read a tutorial for importing avi into Vue. Good grief. It can't import video with an embedded alpha channel? You have to render it separately?
I guess it's like animation master, diffuse image map .. plus transparency image map. -A bit off that it isn't a bit more flexible.

Hmm... actually A:M can use the alpha channel of a Targa image or an imported video with millions+ alpha channel for transparency (using "cookie cutter"). The reason to use a transparency map in a 3D program (AM for instance) is different than importing an image that already includes the alpha. Most apps would allow both options.

For instance AM has a "cookie cut" option that uses an images own alpha channel (targa, png) to define transparency of the surface it is applied to. However you may want to use ANOTHER transparency map for a shape in general that might have several images or none. For instance stamping several color images and then stamping one BIG transparency image over the whole thing. At least it has that option.

I'm just wondering why Vue, considering how cool everyone says it is (it is cool by the way. Haven't used it myself but I've seen what it can do.) wouldn't have the ability to import a video with an alpha channel "built in". This seems to be a basic feature for most applications that import video. It might have to do with versions. Doesn't Vue have different versions? I was reading on one of their forums someone "upgraded" so they could use alpha planes better or something like that.

I'm going to be getting into this type of compositing with a project soon. The particles in AS just... don't quite measure up to what I need. Animation Master has kick arse particles so I plan to composite the particles from AM onto a character in my AS project. Since AM has a built in NLE video editor I'm good to go.

-vern