I am new to after effects and I have need to finish something by friday evening. So I am troubled to ask right away without maybe properly looking online.
my issue is this:
I have filmed someone making a stepping and jumping motion. I wish to place some kind of laser in the movie. The problem is that when the person steps over the laser the laser is still visible through the leg. While it should be behind the leg.
If your laser is an effect in AE, put it on its own layer, precomp it and animate a mask to conceal the beam where necessary. You'll probably need to animate the mask on a frame-by-frame basis. This is a process known as Rotoscoping.
If the laser is a piece of footage, you don't have to use a precomp, but you will still have to rotoscope it.
On a different note: AE is not the kind of application that lets you use it immediately. You have to know the basics first. Here's a good place to start: