View Full Version : Alpha Channel problems!!

08-08-2003, 11:42 AM
I'm Working on a video animation, but I need the ring to be rendered with Alpha, & LW does that automatically, Except I have a glow effect that gets rendered with the Bloom Plugin in the LW processing menu, How do I get the Glow to stay in my Alpha rendered movie, I really tried even to go into the SurfaceEditor/Advanced/Alpha Channel!!! I just don't know how to get this effect that I need to work!
Does any one know-??:confused:

08-08-2003, 11:43 AM
This is what I get_

08-08-2003, 11:45 AM
This is What I need ALPHA

08-08-2003, 12:23 PM
I believe that effects like that are added after the frame has been rendered, hence they won't show up in the alpha channel.
You may need to fix it in post, either by adding the glow in your comping program, or by altering the alpha frames. You could also try changing your objects to white with 100% Luminance and render out a seperate sequence and use that as your alpha.

08-08-2003, 12:47 PM
AHH!! Are you sure thats the only way??:confused:

08-08-2003, 01:00 PM
Well, I can't say that the ways I mentioned are the only ways, just the first that came to mind. Lacking any good solutions outside of LightWave, I'd probably go with my last suggestion. Multi-pass rendering, sometimes with different stand-in objects, is a pretty common practice when one is going for a particular effect or needs to be able to make changes down the road without completely re-rendering a scene. You could just save copies of your modified object(s) and scene(s) seperately for your alpha render. Without a need for any shadows, reflections, etc... the render should go extremely fast.
BTW, what did you do to get your third image?

08-08-2003, 01:18 PM
I mad a Channel in Photoshop using the original ALPHA from LW. I hope that this issue has been fixed in LW 8, this problem comes along a lot, And for one scene what you have suggested it Ok, but when things get heavier, this will start to really bother me-!!:rolleyes:

08-08-2003, 01:42 PM
Actually, the more involved a scene gets, the more one stands to benefit from muti-pass rendering.
As an aside; check out this great thread discussing techniques and uses.


08-08-2003, 04:36 PM
Use Corona instead of Bloom, then check the box that says "Contribute to Alpha"

Generally post-process filters do not add to the Alpha channel, since they are "post".

08-08-2003, 05:20 PM
Hi Toby,
This is like the third or the fifth time that you have save my life, & just when I thought I will give up, you save the day-!!
Thank brother your a life saver

08-08-2003, 05:30 PM
oh it's my pleasure, I'm glad I could help -

and as you can see, Corona is much more flexible than Bloom, you can even put an image into it! I don't know why they bother putting Bloom in there.