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-   -   What is Rotoscoping? (http://www.dvinfo.net/forum/techniques-independent-production/5564-what-rotoscoping.html)

Jim Wiggins December 18th, 2002 12:54 PM

"Rotoscope"
 
What does the artist mean when he used the technique called "rotoscoping" and why is there so much work involved?

Thanks for your time

Jim Wiggins

David Mintzer December 18th, 2002 01:00 PM

It is literally drawing or painting on video or film---frame by frame--that's why it is so time consuming---

Jay Gladwell December 18th, 2002 01:01 PM

In computer graphics, to rotoscope is to create an animated matte indicating the shape of an object or actor at each frame of a sequence, as would be used to composite a CGI element into the background of a live-action shot. 2. Historically, a rotoscope was a kind of projector used to create frame-by-frame alignment between filmed live-action footage and hand-drawn animation. Mounted at the top of an animation stand, a rotoscope projected filmed images down through the actual lens of the animation camera and onto the page where animators draw and compose images.

Robert Knecht Schmidt December 18th, 2002 01:55 PM

Disney's Snow White was rotoscoped from frames of a live actress!

Peter Moore December 18th, 2002 04:02 PM

When fan-films make lightsaber sequences, that's exactly how it's done - you draw white blades over the live blades on the film and then apply glow effects to make it look real.

Jim Wiggins December 19th, 2002 09:59 AM

Thank you!
 
OK. I have heard of this before. Is there software that will track an image within a frame throughout multiple frames and apply the glow effect or whatever to that image. (apply effect to one frame and the software can "follow" the image, generating the special effects over multiple frames)

Peter Moore December 19th, 2002 01:08 PM

I don't think so. You could possibly accomplish this with a blue-screen type technique where the object you want is totally bluescreened (or wrapped in blue) so you can isolate it from the image, but how this will appear in practice I don't know. When you look at raw footage of a lightsaber fight, the blades are often hard to distinguish, especially when there's fast motion. I doubt even bluescreening would make up for this. I think you're going to have to do it the old fashioned way, I'm afraid.

Brian M. Dickman December 19th, 2002 01:43 PM

You got it Jim. Most of the time this is just done with 2D point tracking, doing a combination of intelligent software driven tracking, and human binary search until things match (move halfway from start to finish, fix the points, move halfway from that, fix...). Pinnacle's Commotion Pro is a very popular rotoscoping package, and to some degree the same kind of things can be done in After Effects. Some of the more complex packages can track in 3D as well, so you can let the computer do some of the more complicated work like object rotation.

If you're more interested in the effect, you might check out www.dvgarage.com. A lot of digital effects experts hang out in the forums there, and the site also has some great effect tutorials, including a multipart on compositing where the instructor uses AE to add sabre glow.

Robert Knecht Schmidt December 19th, 2002 02:15 PM

Compositing questions for the experts
 
1) I have a piece of footage with two people crossing into and out of frame. I need to isolate the people from the background behind them. The camera is perfectly static and nothing else in the frame moves besides the people, and since the people move into and out of the frame completely, I have an image of just the background. Is this enough to make a matte that isolates the people from the background without rotoscoping the people? A difference matte doesn't quite seem to do the trick, but perhaps a difference matte in combination with something else...? One complication is the people do leave shadows on the background as they go by...

2) If I have to rotoscope the people, how should I handle portions of high motion blur wherein a body part's edges are indeterminable and parts of the backrgound show through the fast-moving body part?

Barend Onneweer December 19th, 2002 02:50 PM

Difference matte is a fantastic concept, but I've rarely seen it work, and you'd need perfectly clean material to get usable results. And with the shadows cast on your wall, I think your looking at a rotoscoping job...

If you use After Effects or Commotion to mask out the moving people, you can actually apply motion blur to the masks, tweaking the shutter angle in AE to get the right results. You could also manually feather certain masks, since I recommend to create separate masks for upper arm, lower arm, upper leg, etc... But manually keyframing the feather is a pain, and the motionblur often works great. Good luck...

Bar3nd

Jim Wiggins December 19th, 2002 03:03 PM

Thanks again!
 
Brian, thanks for the link! Software application specific - just what I was looking for...

Jim Wiggins

Jim Steffel December 31st, 2002 12:18 PM

I have used Combustion 2 to track masks of moving objects in a scene. The computer does much of the work. However, the final tweaking, the detail work, is very tedious. I have also used Combustion 2 for green screening and/or keying. This work requires a great deal of effort and attention to match the lighting of the two (or more) scenes being composited. Admittedly I am new to most of this, but to me it is a toss up.

Robert Knecht Schmidt December 31st, 2002 12:50 PM

Out of curiousity, jsteffel, what tool is used in Combustion to do the auto-tracking? Is there a tutorial or something on the web just so I can see what this sort of process looks like? Especially, I'd like to know how it is possible to get good masks of objects that have motion blur in a frame (fast moving legs and arms and such).

Jim Steffel January 2nd, 2003 07:28 AM

Rapid, complex movements are not easy to track. They would require frame by frame editing. Tracking moving objects, such as a vehicle or a ball, can be done with little or no frame by frame editing. Complex movements like figures fighting or dancing would better be done with green screening or keying.
Keep in mind I am a relative newcomer to Combustion.
Also, the Combustion tracker can take out some camera jitter by stabilizing the video using reference points.
This link might better explain some of Combustions features.
http://www.discreet.com/support/tutorials/tutorials_combustion.php

Robert Knecht Schmidt January 2nd, 2003 10:24 AM

Alas, all the links on that tutorial page are broken--it's useless.

The closest thing I could find was
http://www.discreet.com/products/com...tutorials.html
but this doesn't offer the keying tutorials that looked interesting.

If anyone has these files saved to their hard drives somewhere, do pipe up...


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