-
Noob Can’t Create Alpha Using Luminance
Self taught Noob, here! I aplogize right up front for my poor descriptions of what I’m trying to do. I don’t even know enough to ask the question right. Thanks for your patience.
Am unable to create an alpha channel in After Effects as described in gnomon training dvd Dynamics 13.
I have created 100 smoke sprites (128×128, tifs) in maya. The images have no alpha channel. (I understand these images to be the incandecence only on a nurbs sphere. The image pulls away from the outline of the sphere and it is impossible to create these images with alpha)
My training DVD outlines a process to take them into After Effects to create an alpha channel.
Here’s what I’ve been doing in After Effects:
1. Import tifs as a sequence. ( I have also imported them as almost every file format available to me in maya. Even those formats that don’t support an alpha channel!) When prompted I have selected “ignore” alpha. Although sometimes it doesn’t prompt me. In which case, I have gone to preferences and set import to ignore alpha.
2. Tifs are dragged into the time line. They are highlighted and
Layer->precompose is selected. In the pop up dialogue I select the top radio button: “leave all attributes in comp”3. I then drag the original tifs into the timeline AGAIN and place them under the newly created comp layer. It is my understanding that the luminance from this this layer will be used to create the alpha.
4. I select effect->channel->set matte. In the box that pops up, for “take matte from” I choose the non-comp layer of tifs. for “use for matte” i select luminance.
5. under the composition menu I select add to render queue. for “render settings” i choose best. for “output module” i click on lossless. In that dialogue box, for format I choose tif sequence and 32 bits. for “channels” i choose RGB + Alpha. for “color” I choose straight.
6. I designate a name and location for the new tifs and render it out.
What I get is tifs with a solid white alpha channel. I’ve changed every variable that appears to be in play. I’ve tried multiple comibnations of variables but no matter what I do, the alpha comes up solid white.
I’ve tried rendering from maya with and without an alpha layer. (which shouldn’t make any difference since i tell ae to ignore any alpha anyway on import?).
Also, What is the best format my images should have coming into AE for this process?
If anyone is proficient in maya as well, maybe they can tell me if I should be rendering with or without an alpha layer when coming out of maya?
My maya is 6.5 and my AE is 5.0
Sorry so long. I’ve hammered at this all day yesterday, last night and again today. I’ve truly tried every combination I can think of on these settings. I’ve read posts to other forums and all kinds of info on alpha channels but the light isn’t coming on. Can anybody help me?
-
3 Replies
-
Hi Tim,
Sorry – can you SEE the alpha channel in AE (when you toggle the show transparency switch at the bottom of the Comp panel) but can’t render it? Or can you not get the alpha to work inside of AE before you render.
You might want to look up Aharon’s AE podcast tutorials on straight vs premultipled to make sure you are choosing the correct render.
Tried moving assets to the new comp when you precompose, rather than leaving them in the current comp?
Simon Bonner
youtube.com/simonsaysfx
-
Thanks for your help, Simon. Aharon’s vids didn’t address my issue exactly but they did get me to poke around a bit. I stumbled across the issue. On the comp layer I activated the “Adjustment Layer” toggle. That was the icon of the half white half black ball ( or maybe yin/yang?). That appears to have done the trick! Thanks for your help! It is really a great thing that people can get help on this site! MOOOOO!
-
Ahhh! Well, glad you got it figured out.
Simon Bonner
youtube.com/simonsaysfx
Reply to this Discussion! Login or Sign Up