i am very new to After Effects and don't know much about it.
i am making a movie which requires me to cut out an object from the clip and i manage to do so quite nicely, however once exported, it has a black background behind it.
i need to get it transparent because i am making a projection mapping uni project and cannot blend all the parts together when they all have a big black border around them.
please can anyone help me?
After verifying that your comp has a transparent background by either checking the alpha channel or enabling the transparency grid add the comp to the render cue and pick the lossless with alpha preset from the pull down in the output module.
If that makes no sense at all to you then type rendering in the Search Help field at the top right corner of AE and study the links.
BTW, media players will not show you a transparent background, you'll need an app that can read them like AE, PPro, C4D or other compositing or 3D apps that can read alpha channels on video.