render with alpha channel

IdotT wrote on 3/27/2010, 10:01 PM

Is it possible to render a video with an alpha channel. I have cretaed an animated sequence (an explosion) with three layers of video, each one has an alha channel, I now need to use this and move it around in a scene. What should I use?

Comments

jetdv wrote on 3/28/2010, 1:23 PM

Try "Uncompressed" AVI, open the "Custom" option, and check the option to include alpha channel.

Eugenia wrote on 3/28/2010, 1:31 PM

Uncompressed is way too big. Try Lagarith, with various of its options, until you get some alpha channel. Or, you can try AVID DNxHD.

jetdv wrote on 3/28/2010, 2:19 PM

Depends on how long the sequence is. If it's a 10 second lower third, it's not too bad. There's also some Quicktime formats that support alpha channel. Plus, a PNG image sequence would also work.

IdotT wrote on 3/28/2010, 10:50 PM

Hi thanks for your help, I tried AVI uncompressed as suggested which worked well and gave a file of 40.000 kb, I downloaded Lagarith and the file was 8,000kb which is much better at the moment.
One thing I noticed was that AVI render show thier alpha channel in the project media window while the background with Lagarith remains black. I didn't realise the alpha channel was working until I dragged it onto the timeline.

Eigentor wrote on 3/29/2010, 10:15 AM

Ok, so what is "alpha" channel and how/why would I use it?

IdotT wrote on 3/29/2010, 7:44 PM

Hi Alpha channel as I use it a transparent layer sometimes in addition to RGB.
I'm using it to put layers of firework animation together with sparks, flames etc all being created seperately and then arrange in vegas. I'm sure there are many other ways to use it.