posted 05-30-2000 09:53 AM
It's easy to create a movable mask in After Effects. (Unfortunately, it's not really possible to do in Premiere, but you could work on a frame-by-frame basis on a filmstrip file in Photoshop... i've done it before) Anyway, in After Effect:- Create a mask; enable the icon next to the mask's "Shape" property to allow it to change over time. Add some feathering (a few pixels only).
- Double click the clip name to open it in a separate window with the mask visible.
- Start with the first frame; move the vertices of your mask to the shape you want; add vertices for a more accurate masking; add curvature to segments if needed (I only had one curve in mine).
- Go to the last frame of the clip and move the mask's vertices for the new situation.
- Go the middle of the clip; do the same. Repeat for other frames. You have to do enough keyframes for the motion to look right. It might be 1/3 frames or 1/5 frames depending on your situation. You probably won't have to do every frame
In the case of the missing head I had a few fixed vertices (at the corners of the closet). All the others (about 10 more) were moved to follow the actor's shoulders and neck.
BTW, it's easy to make a mask for a simple situation like this (took me 1/2 hour to film the clip, capture it, do the effect, upload it on a server and write a message to the board about it!), but for anything more complicated, you should use blue-screening.
The advantage of the masking method are ease of setup (no screen, no need to worry about uniform lighting), no blue-screening artifacts (color bleed, "weird" edges). But it becomes a pain if the mask is too complex!
posted 05-30-2000 09:01 AM
