by Nadine Matesowicz
Tips:
- When rotoscoping it is far easier to duplicate a mask and alter it as needed as opposed to trying to animate a mask, because there can be all sorts of issues when changing the number of control points.
- When dealing with masks, I have found that it is easiest to create a nice mask while the mask settings are set to None and the opacity of the mask is left at 100%. Once you have completed tweaking the mask, then you can change the mask to the Subtract setting.
- While masking a scene, I have found it helpful to keep a log of the masks to help keep track of which mask is active on a particular frame. This made my life much easier when going back to do clean up work because, for the most part, each mask was only opaque on a single frame.
- The shortcut keys for moving through the timeline frame by frame are page up and page down.
- Finally, remember that this can be a really slow and tedious process so plan accordingly. It’ll take more time than you think.
Ok, this tutorial is going on the assumption that you already have experience with After Effects and have already imported the footage to rotoscope into a project and moved into the timeline (with the footage to be masked making up the top layer). Image A
Image A
First, be sure that if you have more than one layer in the timeline that you have the one to be rotoscoped selected. Image B
Image B
Image C
Duplicating a Mask
To duplicate the mask go to the Edit menu and select Duplicate. Image D
Note: Make sure that you have the mask selected to be duplicated or After Effects will duplicate the layer containing the mask.
Image D
Once you have duplicated the mask, you can set the keyframes for the original. Seeing you are creating a mask per frame, the keyframes are going to be set under the opacity setting. The frame that the mask should be visible at should have 100% opacity and the two frames that sandwich this frame should have their opacity set to 0%. Image E
Image E
Example: if Mask X is supposed to be visible on frame 73, then the opacity should be at 100% on frame 73. Frames 72 and 74 should have their opacity set to 0%.
Note: Make sure that you have changed the Mask properties to Subtract, otherwise the frame will look the same as before creating the mask.
Continuing
The rest of the process is just a matter of repeating the above steps until you have taken care of every frame. Just remember to keep a log because it’ll come in really handy if you have to go back to do some clean up work due to jittering and other such things caused by the masks being irregular.
Clean Up
In order to do your clean up work, be sure to remember that the pen tool is your friend. If you find that you don’t have enough control points, the pen tool can add another one wherever you need it along the mask to help you smooth out curves. Not only that, but if you have too many, you can use the pen tool to subtract some control points. This can also be done with the selection tool by selecting the control points you want to get rid of and hitting the delete key.