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Roto Scoping in Motion 5
How does one rotoscope in Motion 5?
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37 Replies
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I’m only in Motion 4, but I expect it might go like this:
Import your original movie and set it as the back plane.
New layer, use the freehand bezier tool to trace around the subject in the frame. Choose if the inside or outside of the election is filled with black or whatever.Advance one frame, repeat.
If I have to do roto, I export the clip as a series of targas or a tif sequence, and do it in photoshop, using the “extract” filter to roughly go around the outline and then fill it. If you combine this into a batch action that will save the frame and advance the next one, you can power thru a short shot relatively quickly. Then export the stills back to the timeline.
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[Mark Suszko] “Advance one frame, repeat.”
The general consensus among roto artists is that this is not the best way of doing it.
It is preferable to do frame 1 then advance say 20 frames (more or fewer depending on the speed of the movement) and do that frame and so on. The software does a smooth interpolation between these major keyframes, and you can easily go back over and add intermediate keyframes as necessary where the results are not as accurate as you’d like. A good way is to check at the half way point between those two major keyframes and correct as necessary, and keep subdividing by half, always with the view to getting the software to do the best interpolation.
The reason not to go frame by frame is that there will be no interpolation smoothing at all and the roto will “boil” dramatically. The bottom line is that the software is much better as creating a smooth result than can be done entirely manually.
For more details see Ron Brinkmann’s compositing bible The Art and Science of Digital Compositing which has a good rundown of the basics of rotoscoping.
Simon Ubsdell
http://www.tokyo-uk.com -
I actually knew that, and that’s my flow when keyframing an animation, but in the classic actual film rotoscoping in pre-digital days, they had to do it that way, frame at a time, in order. I was referring to it in shorthand, guess I should have been more precise.
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[Mark Suszko] “I actually knew that, and that’s my flow when keyframing an animation, but in the classic actual film rotoscoping in pre-digital days, they had to do it that way, frame at a time, in order”
Absolutely – it’s amazing they achieved the quality of roto they did back in the day.
Apologies for picking you up on this. I thought you probably knew the official way to do it, I just thought I’d make the point in case anyone was trying to do it the frame by frame way and didn’t know any better.
Simon Ubsdell
http://www.tokyo-uk.com -
I am happy you made the point about doing it every 20 frames or so. I would not have known that.
What soft ware are you referring to? Motion5? Are there people doing this in M5? Any examples?
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[Lawrence Diggs] “What soft ware are you referring to? Motion5? Are there people doing this in M5? Any examples?”
Yes, you can do manual roto in Motion just as well as you can do manual roto in After Effects, though not as well as you can do it in the high end compositing packages.
Every case of roto is a bit different so it’s a bit hard to give general instructions.
One other key tip that I didn’t mention is that before you start keyframing individual control points, it’s a good idea to go through and keyframe the overall mask shape (again at regular intervals), as this will save a huge amount of effort and generally make for a smoother result. You can then go back and fine tune the control points once that step has been done.
And a further tip is that if you’ve got a complex object to cut out – humans beings and their various body parts are a prime example – the way to go about it is to break the complex shape down into component parts rather than trying to do the whole thing in one go. That means that you’d do the arms separately from the body, and even the fingers separately from the whole hand (depending of course on how far you are away from the subject). That may seem like more work to start with but it really pays off in the long run – you’ll only end up kicking yourself if you try to do a shape that’s too complex because it will be so much harder to control, and it just won’t look half as good.
The bad news is that roto is mostly very, very slow and time-consuming – and just downright hard work – and that’s the same on pretty much whatever system you’re trying to do it on, although the top end stuff does have a few tools to automate certain parts of it.
At the budget end of things After Effects gives you RotoBrush which does do a pretty decent job of automating the task to some extent if you’re not too pedantic about the results. RotoBrush does depend on the subject being reasonably distinct from the background, which of course is not always the case. This is why the human element will always come into play to some degree – you will instinctively know what is foreground and what is background much better than any software can currently manage.
Simon Ubsdell
http://www.tokyo-uk.com -
OK, so here’s one more really important general roto tip that is well worth remembering before you start.
Always try and get some kind of procedural matte before you jump in and do a complete roto.
In other words, see if you can get part of the way there with either a luma key or a chroma key (these are the commonest types of what are known as procedural mattes).
Procedural mattes will almost always give you a better edge than you can get with roto, plus they can of course save you a ton of work which is an even better result!
Add a roto (or several) to tidy up the bits that you can’t separate from the background with the procedural matte and combine the results into a single matte.
Simon Ubsdell
http://www.tokyo-uk.com -
Are these all available in M5?
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Lawrence,
The tools used to create procedural mattes (i.e. chroma and luma keyers) are available in Motion. Procedural mattes aren’t a stand alone filter or tool that you apply, they’re the process used to create a matte. Not so much the “what” as the “how you get to the what.”
Barend Onneweer did a tutorial a while back on the cow explaining how to go about creating a procedural matte. It was written with After Effects in mind so you might have to do some fiddling if you’re working in Motion and haven’t opened the keyer but it should translate simply enough with a little effort. Link can be found below.
https://library.creativecow.net/articles/onneweer_barend/keyingtut.php
“Whether you think you can or can’t, you’re right.”
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Thanks a lot. I will check it out.
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