Blackmagic Forum

Hi guys

i was wondering what are the best options for roto


-the wand tool?
-mask and trackers?
-1st frame, last frame then fill the middle?


Also when do you the frame by frame process as a last resort?



If there are better and newer ones, let the community know

Please and thank you

The usual stuff:
- use shapes with less control points (use Bezier curves with two handles only when really necessary);
- break your focus object into pieces that don't change shape much;
- use as much full shape transform and as little individual point manipulation as possible;
- only roto positive space (don't try to roto empty space between objects, use shape combining and mask/stencil ops instead);
- analyze the movement of focus object, approach it like animation;
- choose either inner or outer edge and stick to it, don't roto mid-edge (in the middle of soft edge);

Keyframe the roto like anination, extremes and breakdowns first, then fill in for accuracy if necessary. For fast-moving shapes and jerky motion you probably get to the frame by frame sooner or later. For speed, try to use trackers, planar tracking is very helpful (Mocha is the boss here).

All kinds of wands, rotobrushes etc usually is a recipe for crap, use keying if it works instead.

Agree with everything Hendrik said except:

Hendrik Proosa wrote:All kinds of wands, rotobrushes etc usually is a recipe for crap, use keying if it works instead.

That's kind of like saying "ride a horse, these internal combustion engines are usually a headache." We're in early days on assisted roto like Adobe rotobrushes. Shortly, they will be much better.

In the early days of combustion engine they were a headache. I'm not against them at all, but if you have to choose between painful innovation and getting the work done, you choose what gets the work done. When that "shortly" comes, I'll be all over it.

depending on the objects being rooted, you can also look at the interval technique where you adjust every 12 frames (based on 24fps footage), then go back through and do every 6 frames (which would then be the in-between frames. Then tweak from there. The obvious downside is the amount of keyframes, but you get a lockdown of the motion. The other thing you have to be careful of is you want to limit the amount of keyframes close together as the roto can look jittery or popping.

Definitely analyze the motion of the objects you intend to roto and as mentioned above, look at it from an animation standpoint and break down the object into individual moving pieces. Even hair sometimes needs multiple roto nodes due to how fluid it can be when it moves. Sometimes I use circles to roto wavy hair.

The downside to this method is that it works best with lineair motions. Say an arm moves from left to right in 12 frames, but it actually only starts to move at frame 3, then slow down at frame 7 and then speed up at frame 10 again. In that case splitting your frames up in half will work against you.
I think that's what they mean by looking at it from an animation standpoint: analyze the motion first and then find the keyframes in the original movement to help you plan out your roto.

An Interesting Theme.

How do you Roto very small People, Peaces which have at the end 10 Pixels hight in a 2K Shot. Is this a job for Silhouette FX or Mocha or other techniques?

An Example is here the crowd, horses, people with wimple at 01:03 min - where Background are a Set Extension.



It's an issue which i have very often...