CPSC 526 Class Wiki

Test post for paper discussion.

-- MichielVanDePanne - 04 Nov 2011

Contribution:

Virtual characters are represented as directed graphs having nodes and connection. A genetic language based evolution of motor as well as neural control is suggested. No user information regarding shape/size, joint constraints etc are assumed when developing the creatures.

Computation of results:

Since the entire task is computationally expensive, parallel implementation of the task is done. Evolutions of about 50 to 100 generations i.e. by mating directed graphs either by crossover operation (30%) or by grafting(30%) and sometimes asexually (only using mutations) (40%), are performed corresponding to four types of behavior, i.e. swimming, jumping, walking and following. Another suggested method was to interactively evolve a morphology so as the creatures have aesthetic touch to them instead of just goal based evolution. Hybrid world creatures were also developed.

Reproducibility:

My view is that the paper is reproducible. Although models are not detailed mathematically, they make up for it by giving exhaustive description of the same. The models used for sensors, nerons and Effectors are detailed properly in section 3. Details about the use of physical simulation techniques e.g Feather's method to calculate accelerations, Runge-Kutta fehlberg method for integration and other details for virtual world simulation (e.g water, collison etc) are provided in section 4. The genetic optimization based behavior selection method is also well explained in section 5.

Improvements in Research/Writing:

Overall the paper is well written but I would have preferred some more light to be thrown on the technical aspects of the overall model and specially the modeling of characters as directed graphs and the genetic evolution process.

-- Main.sumanm - 17 Nov 2011

Above is the review of : "Evolving Virtual Creatures"

-- Main.sumanm - 17 Nov 2011

Review : "Practical Character Physics for Animators" Contribution: - Interactive system to enhance character motions, by incorporating physical properties into a existing key frame system. - Tools to enhance realism of balistic motions. - Investigate physical accuracy of manually created animation by skilled animators.

Result Evaluation:

1. Ballistic Paths : The path is created based upon the center of mass m and a constraint. The animator has 2 ways to incorporate this into the animation, either by adjusting the timing of the motion, freezing the initial and final positions or manualy adjust the path and then retime the entire motion.

2. Angular Momentum: An iterative approximation algorithm is suggested to compute the configuration (T_o) of the character given the momentum (h) specified by the user. THe method makes use of the rigid body inertia (J), velocity (v_i), the position (x)

Reproducibility:

The paper should be reproducible to a considerable extent. All the techniques used are backed up with corresponding pseudo code/step-by-step algorithm. The variables are clearly explained in both the cases of ballistic path and angular momentum. An appendix explaining the background on the equations governing the physical properties of an animation is also provided for assistance.

-- Main.sumanm - 17 Nov 2011

"Practical Character Physics for Animators"

a) Contribution This paper contributes an extension of the traditional keyframe-based animation authoring interface that includes visualizations of physically correct motions. The goal is to provide tools and feedback to animators to allow them to produce more physically accurate motions, without removing any of the animator's control.

b) Evaluation The system is evaluated by having professional animators use the tool, and by comparing the physical accuracy of animations produced with and without use of the tool.

c) Reproducibility The tools described in the paper are certainly reproducible, as the algorithms used are given in sufficient detail to recreate them. The success of the tool in terms of usefulness to professional animators is not as certain to be reproducible, since not many details of the authors' specific evaluation methodologies are explained in the paper.

d) Improvements There are a number of spelling and grammar errors present in the paper that require correction in order to improve readability and understandability. Furthermore, the figures and tables are all clumped at the end rather than located near the relevant section of the paper's body, which also makes it more difficult to read and understand exactly what the research is accomplishing.

-- Main.cdoran - 17 Nov 2011

Evolving Virtual Creatures

What is the contribution of the paper?

In previous work, control system must be designed for each type of fixed structure. The method in this paper can generate physical structure and its corresponding control system automatically in a similar fashion to creature evolution. So the generated physical structure and the control system is also called a creature. Users don't have to specify any parameters of physical structure or control system. The generated physical structure and control system work in 3D physics.

How are the results evaluated?

The results are evaluated by looking at the generated creatures in various environments. An important concern in the evaluation seem to be how well creatures can adapt to the environment by performing expected tasks, i.e. does it swim or walk fast, or does it jump high?

It is also evaluated by the number of generated creatures and the time it takes to do so.

Is the paper reproducible?

Somewhat reproducible, but it's not clear to what genotypes look like and how they can be converted to creature morphology and creature control.

how could the paper research or paper writing be improved?

Overall, this paper is well written, but in the introduction, there is not an overview of sections two through six and how those sections are related to one another. It would be nice if they do so.

Practical Character Physics for Animators

What is the contribution of the paper?

Traditionally, animators use keyframing and inverse kinematics to animate characters. This paper develops an interactive system that allows animators to create physics-based characters which makes the motion more physically plausible.

How are the results evaluated?

The results are evaluated by the physical realism of the animation.

Is the paper reproducible?

It looks to be reproducible, given the equation to compute ballistic paths, and those equations and the algorithm needed to develop the angular-momentum tool.

how could the paper research or paper writing be improved?

Section subsection headers can be more meaningful. For example, section two "Improving Physical Realism" and section three "Keyframe Animations' Physical Accuracy" look similar to each other and they don't seem to summarize the respective sections very well.

Main.shuoshen - 17 Nov 2011

--Practical Character Physics For Animators

• contribution: It was the first research that incorporated physical properties into an existing key frame-based system by the time the research was conducted. Tools were developed to help animators modify ballistic motions of characters and the physical accuracy of the high quality animations was investigated by measuring important physical properties.

• evaluation: Basically, the tools were tested by animators and the evaluation was based on the effectiveness of how much it helped the animators to create the physical realistic animation.

• reproducibility: I think the tool is reproducible since the basic idea is not hard to understand, and the math details are provided along with appendix. However some of the results seem to be less reproducible since it requires professional animators to create the ballistic motions, which could be uncertain.

• comments: Overall the paper is not hard to follow. However the structure of the paper is not clear when I first read it. I have to go back and forth to get clear about the organization. I also encountered a few issues. For example, the term “COM” was not explained, at the beginning I could only guess it is “center of mass” which could also be “center of momentum”. The paper also has a number of grammar or spelling issues such as “derived form”. But given the factor that this is a preprint version, the author may have corrected these kinds of issues in the final version.

--Evolving Virtual Creature

• contribution: The research creates a novel system for creating virtual creatures behaving in 3D physical world. The creature’s morphologies as well as their control systems are evolved. “A genetic language is presented that uses nodes and connections as its primitive elements to represent directed graphs, which are used to describe both the morphology and the neural circuitry of these creature.”[Karl Sims]

• evaluation: The experiment runs in parallel with one master node performing the genetic algorithm that chosen randomly from asexual, crossovers and grafting, and then sending out genotypes to other slave nodes to do fitness test and then gathering back the fitness values. The fitness tests include swimming, walking, jumping and following. After 50 to 100 generations, creatures that pass the fitness threshold survive and get selected.

• reproducibility: In my opinion the paper should be reproducible however it will involve large amount of work since the models used in the research are presented without detailed mathematics explanation. And I still don’t quite get how the phenotype “brain” is generated. But I think the physical simulation part shouldn’t be that hard since we use simplified models.

• comments: Overall the paper is well organized and I found the structure is not hard to follow. However it takes time to learn some background knowledge.

Baoxuan Xu

* Contribution: In previous research, the control system can automatically be formed rather than design for specific physical structure. Users don't need to care about the detail shape of the object and it works in 3D space.

* Result Evaluation: This paper use several environments to evaluate the result. The performance time is concerned. And also, this system might work in different jobs, thus they test it by making the model do many kinds of motion and evaluate the physical realistic animation.

* Reproducibility: This paper is OK to reproduce. Maybe it is hard for us to regerate some math methods and those models.

* About the improvement: It seems no fruitful background and relate previous work for use to understand the breakthrough of this paper in a comprehensive view.

* Contribution: The new interface based on keyframe-based animation is pretty good for users to see the parameters and details more clearly. In this sense, user could understand the system very well and the result could be regard as reasonable.

* Result Evaluation: The evaluation include the effectiveness concern, which is not in detail numbers. By scaling the characters, the result are concerned by seeing the stableness and errors.

* Reproducibility: The mathematical processing has been discussed in the paper and the method in itself is pretty straightforward to understand. Thus I think it is reproducible.

* About the improvement: The writing before the result has no pictures to illustrate the work in a viewable way.

-- Main.Jingxian Li - 17 Nov 2011

Evolving Virtual Creatures

The paper contributed by introducing a method for generating and testing simple hierarchical feedback-responsive creatures in a thought-provoking demonstration of structured behavior evolving from utter randomness. This is essentially a step forward towards automated creation of new and interesting solutions fitting a limited set of behavioral constraints set by an animator and letting a computer take care of the "creative" generation. From an AI perspective, this paper demonstrates an alternative towards the hard task of designing intelligent systems by throwing computing power (chaotically, yet wisely) at the problem.

The results were evaluated based on combination of subjective or arbitrary discrimination and optimization of an objective score based on success in a few low-level motion tasks. However, the paper did not describe fully the process for discriminating against evolutionarily slow developers and genuinely poor ones. This appears to leave out the possibility of a beneficially unique behavior (but poor survivability) by chance combining with general survival traits. It is also not well described how two creatures evolved to do two separate tasks can combine to do either or both tasks. These would have been helpful to help shape complex motions useful for an animator.

While the process is described, the paper does not appear to provide enough information for others to easily reproduce the findings. It does not provide sample or reference implementations, and does not provide background for the techniques used for the network implementation on the parallel architecture. It does not even provide the metrics and examples of the objective functions, parameter, or constraints in the cherry-picked creatures shown. While their stance that the idea is not to understand the design process, the images and videos do not tell whether the mechanics behind the behavior are actually practical or meaningful. -- KevinWoo