Rotoscoping

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Definition

Definition(external link) (cache) The practice of using frames of live footage as reference for painting animated sequences. While the painting will always be down to the skill of the artist, modern graphics equipment integrated with a video disk store makes rotoscoping, or any graphical treatment of video frames, quick and easy. This has led to many new designs and looks appearing on television as well as more mundane practices such as image repair.

Example

Image Image
Image Image

Tracking

By tracking the object to be roto'd first the job become quicker.

2d Tracks

A large amount of the cameras or objects movment can be added to the roto main transform with a track. If using more than one point make sure your track are accurate as noral tracking issues occue i.e. scale and rotation jitter. Depending on the avaliable points to be tracked a 4point track can help if the object is twisting (i.e. face turning from side to side) or you have a plane to track and dont need to do it with a 3d track. Screen/sign replacemants can also use multiple track points, in this case the roto points can be connected to the track points rather than the main transform of the shape. http://www.simplycg.net/viewtopic.php?t=1853(external link)

3D Planar Roto

Using a 3d matchmove track.
  • If you can put all your rotos on planes then the MultiPlane(in shake or similar tool that can import a 3d track) can turn a three day roto into an afternoon. i.e. its great for objects stuck to a plane, or a starting point to get the cameras moment on your roto.
  • Alternatively 3d tracking tools can export out two or four point tracks for specific packages
http://www.simplycg.net/viewtopic.php?t=3554

Issues & Tips

from Scott Stewart tutorial(external link)
  • Think Like an Animator (Keyframe)
  • Use as Few Points as Possible, Then Try Not To Move Them Individually.
  • Use Multiple Shapes
by Scott Stewart(2004)
From digitalGypsy blog(external link) (cache) While rotoscoping moving people, I tend to use several different nodes for each part of the body. Hands, arms, legs, torso, head. Depending on your compositing package, this will make deleting or redoing any section of the person easier. Don't set keyframes on every frame, or even every 5 or 10. If you're rotoscoping a human, you'll want to match the cadence of their walk or run, so keyframe the roto on the highs or lows of their gait. You will want to use a tool that allows you to have soft edges, so that motionblurred frames of the person will accurately be rotoed. If you're going to be rotoscoping objects, like cars, boxes, things that are usually inanimate, you can use one complete roto to cover the entire object. However, if there are extreme perspective changes, it might be better to use different roto for different parts of the object. Sometimes for objects like these, you can roto the first frame, and track the object throughout the shot duration. by Digital Gypsy (2005)
from FXGuide artical on rotoing(external link) (cache) Some skills remain necessary, including a sense of what is important. "One of the hardest things for people to do in our department is to realize that they're looking at a very zoomed-up plate," Mongovan said. Also, he pointed out, a movie audience will see an image for only 1/24th of a second, too short a time to register flaws that may torture the artists. More important is consistency. "I tell people, 'You can paint that first frame wrong, just keep it wrong it all the way through.'" That kind of understanding is key, Bertino agreed. "The secret to good rotoscoping has always been -- regardless of what it's used for -- an educated eye and good judgment as to what to include and what to leave out," he said. "Most people think the rotoscope is very literal -- you trace what's there, and that's it. It's possible to put too much detail and confuse matters. You need to have that sense for judicious editing. That hasn't changed at all. And not everybody's got that by Matt Silverman(2004)
VfxTalk Thread(external link) (cache)
  • Break up the object into multiple masks... this does 2 things. It allows you to key each part of the body/object based on it's motion, and 2, allows you to redo one part that may not be working, without losing it all.
  • as above, be sure to make keys on the basic motion as your first pass. so in the case of a character walking, on one of his leg masks, you would set a key when his foot plants, one in mid stride, one on the frame that his foot comes off the ground, and a fourth on the swing. From here you can then go into sub-divide the motions, and make sure your alignment is correct.
  • Be sure to move your points in groups. I can't tell you how many times i've watched people move each point individually... not only is this slow to animate, but it also introduces subtle variations in the edge of your shape, and you will end up with the wobblies...
  • track the object if you can... I quite often will try to track the subjects head, or belt buckle and attach all my roto to the path... this will then mean that the roto is more about changing shape, and less about where on the screen the shapes are.
by Jason Kolodziejczak(2005)

Links

External Links


Created by ome. Last Modification: Sunday 04 of January, 2009 17:08:51 GMT by ome.
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