Motion Capture Editing

Paper One

This is an example response. To add your own response, click on 'Edit' above. Paragraphs are separated with just a blank line. This paper is interesting because... It is flawed because ... I didn't understand the following bits... Open problems are ... -- Michiel van de Panne

Another paragraph. Replace this text. Motion signal processing

It is a good idea to apply the techniques from image and signal processing to animation. It provides another alternative to edit the captured data. But when considering the constraints for the real life characters, it is hard to describe those constraints in the format of signal or image processing (I suspect but not sure). Maybe the resulted motion is not realistic. -----jianfeng tong

Some criticisms: - Affine deformations (translation aside) don't seem to be very useful for describing changes to human/animal characters (or any object with limbs/projections). It seems like for them, the key-shape deformations would do all the work. - Sub-part decomposition is a sensible thing to do, but greatly complicates the process (since a human must mark which contours belong to which part). - I don't know much about animation, but it seems that knowing/having the contours of the animated characters is unlikely... (unless they used a computer tool). - Using colour to extract the foreground (character) is a cheap trick that won't work in many situations. - In the 3D case, there seems to still be a heavy burden on the animator. Once they've created their output key-shapes, how hard would it be to do ordinary keyframing??

-- Overall: It's a cool idea, but not only very crudely extendable to 3D.

-- daniel eaton

Motoin Capture Cartoon paper : While the idea of "capturing" the animation off an existing 2D animation sequence sounds great, the way the paper presents it, there seems to be a lot of user input and prior assumptions necessary to make it work (contours need to be provided, or assumptions about region colour is made). Also, extending the motion to 3D sounds costly and inaccurate. Overall, it's great to be able to reuse animations and apply them to create new ones, but it seems like there is almost as much work involved as doing it yourself to begin with. -- Roey Flor

(Motion signal processing) I usually find it quite interesting to see techniques discovered and developed in one field applied in another, but in this case, I found the results less than satisfying. Watching these animations in action may have been more convincing, but the descriptions and figures did not seem like very impressive results, and on top of this, their methods introduce constraint violations which almost seem to outweigh the benefits. What they believe "to be the most useful" of their techniques, motion displacement mapping, looks like an awkward and unintuitive method way of modifying a motion. I would think that directly modifying a pose of the character, and seeing where that new pose lies on several motion signals may make this method more approachable. -- H. David Young

Paper Two

Another paper. Please add your comments below.

It provides a new method to describe the captured motion which is done by recording affine deformation and key-shaped deformations. And then those information can be retargeted and reused. Through this method, the traditional animation resources can be utilized as motion captured data. In this paper, there is not much information on the extension to 3D models. In the above two types of captured information, there is not enough data provided to do the extending. it that right? ----jianfeng tong

- 2.1.2, They use the same band gains for all DOF. This doesn't make sense to me -- I doubt you would want to amplify all of them equally (and some not at all). They use the example of a nervous walk, but with this approach it's more than the walk that's nervous/shaky, it's the entire body. And, if they were to allow for individual DOF gains, then they're almost back to square one, since the animator has to adjust each DOF separately. - Why don't they just use an FFT? - Waveshaping doesn't seem very useful... the examples they give aren't compelling (joint limiting is trivial, and I don't think it's very intuitive to produce these curves to add 'undulations'). - I've seen DTW referenced many times in animation papers, is this the first paper to introduce it to the animation community? - Motion displacement mapping: how does this compare to what IK/constrained optimization would output? It seems that, in fixing some constraints, this technique might cause other constraints to be violated.

-- daniel eaton

(Turning to the masters: motion capturing cartoons) So much of the technique shown in this paper requires a lot of human involvement that I am curious as to when the motion should be recovered and when it would be more efficient to recreate it. I also found it kind of funny that they mention having data from a cartoon made with a computer tool; if such data was available from the original tool, I would think there would be much more affective ways to re-target the motion. -- H. David Young