Animation as a Trajectory Optimization Problem

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

In “spacetime constraints” paper, it presents a neat method for animation, using physics model and some objective functions, and then letting system automatically figure out how the motion should be performed. Having said that, the performance of the approach still heavily depends on constraints set by users; and moreover, finding an appropriate objective function and whereby solving for optima are also quite challenging. As it said “the realism of simulation comes at the expense of control.” In “particle” method, it mentions SQP solver, so it would be good if we can reveal a little bit about how it works. -- Steven Chang

(Spacetime Constraints) I didn’t read very carefully but it’s amazing that the program can understand commands such like “don’t waste energy” or “come down hard enough to splatter whatever you land on”. What I’m curious is that how could the program know what the animators mean? There must have some patterns that should follow. So then the program can do only what it has been taught to do which limits its performance. Thus it still needs much human efforts to define such constraints with the program. The ultimate goal on this research area might be building the system that realizes generating animation by what-you-say-is-what-you-get model. But seems it has a long way to go.-- Zhangbo Liu

Paper Two

Another paper. Please add your comments below.

This “Synthesizing …” paper presents an interesting approach to generate realistic motions by solving the optimization problem in a low-dimensional space. Projecting human motions onto an abstract low-dimensional space is based on the observations that many dynamic human motions can be adequately represented with only five to ten degrees of freedom. However, after watching the movie, I am wondering whether this is surely adequate for some complex motions other than jumping, walking and those presented in the movie. Similar to first paper in that animators also have to select a set of motions as references, I think the performance could still be an issue; but they also use IK solver to enforce the kinematics constraints, so the result should be more accurate and realistic. -- Steven Chang

(Synthesizing Human Motion) Once I’ve read the Neuroanimator [Grzeszczuk et al. 1998] and it was very interesting. I think this paper did the similar work as that one. There do have several methods of using low dimension physically-based model to emulate and control higher dimension physically-based models. But a common issue I think is to balance the realistic effect and the computational workload. PS: I tried several times to watch the video but I didn’t observe obvious difference among the motion under 2, 5 and 10 dimensions.-- Zhangbo Liu