Animating Outlines?

[Lars Bunch]

Hi,

I assume you are going to shoot this footage yourself. If you could shoot this on a greenscreen, then you could just pull the matte from that and you’d have your shot. If you can’t work with a greenscreen, you might try shooting a clean plate (ideally with no traffic or movement in the background) and then, without moving the camera, have the car drive in and the actor walk out of shot.

You could then create a difference matte based on the clean plate. You’d probably have to do some roto to clean it up, but that might be one approach that could work.

If you needed vector lines to work with, after that, you could do and auto trace on the matte.

Lars

[Zygotesoup]

Well, I’m most likely not going to be able to shoot at a green screen that large, so I’m going to have to figure something else out. I have a feeling this might be a little over my head since I don’t know what a difference matte is and ive never done rotoscoping. Can anyone reccommend any tutorials that might help me understand this a little better? I’d really like to make this effect work for me. Thanks.

[Roland R. kahlenberg]

A Difference Matte is created by looking at TWO footage items and ten creating a matte of the difference between them. Say, you’ve got a footage of a wall. To make things simpler, let’s assume that there’s no camera movement of any sort. On another shot, same camera, same everything; you’ve got a car entering your shot and stopping.

So, now you’ve got two shots
1) wall and nothing else
2) wall with car entering screen are

You would then apply a Difference matte to either layer (doesn’t matter). Within the Difference Matte’s Effects Control pane, you’ll find a parameter for selecting the second layer from which to pull out a matte. So, you may want to apply Difference Matte to the wall layer and then select the second shot with the car.

The trick is to find a backplate that is as consistent as possible – lighting issues, no movement from elements, watch out for shadow/sun movement, trees/leaves, people etc. Once you find a backplate that allows for the most control, you’re about half the way there.

The next bit involves knowing how to massage your matte once you’ve apploed Difference Matte. Lots of techniques here and you may actually be using more than one, including masking.

HTH
Roland Kahlenberg
https://www.broadcastGEMs.com – Adobe After Effects Project Files
https://www.myspace.com/rorkrgbspace

[Zygotesoup]

So, if I’m understanding this correctly… the difference matte compairs the 2 pieces of footage and creates a matte in the shape of the objects that are different??? I think I’m gonna have to play around with it to really understand what it does.

[Roland R. kahlenberg]

[zygotesoup] “So, if I’m understanding this correctly… the difference matte compairs the 2 pieces of footage and creates a matte in the shape of the objects that are different??? I think I’m gonna have to play around with it to really understand what it does.”

YEP! The AE manual covers this with a simple pictorial example. Check the Help->Effects menu item and there should also be a similar example.

HTH
Roland Kahlenberg
https://www.broadcastGEMs.com – Adobe After Effects Project Files
https://www.myspace.com/rorkrgbspace