Difference: CPSC526ComputerAnimation (10 vs. 11)

Practical Character Physics For Animators (Ben Humberston comments)

Contribution The authors present a group of tools that provides visual feedback about the physical accuracy of an animation during character animation authoring. They provide three specific tools:

• Ballistic trajectory: A simple visualization of a point-particle trajectory through the air; the user may modify the start point, end point, time in air, and initial velocity to achieve a desired path, then modify their existing keyframed animation to better fit the ballistic path

• Angular Momentum: The character's angular momentum during free flight is calculated, and the character's root orientation may be adjusted to preserve the calculated value.

• COP/COM: The projection of a character's 3D center of mass/pressure is shown on a flat 2D plane beneath the character along with the support polygon of the feet.

Additionally, the authors provide observations on the physical errors in animations created by professionals without the use of the paper's tools.

Evaluation The authors only provide subjective evaluation of their system's usefulness for animators. They put strong emphasis on it's effectiveness as a standardizing tool among multiple animators in a studio, suggesting that the satisfaction experienced by solo animators when using the tool may be quite variable. Additionally, they provide no controlled evaluations of perceived animation quality that compares animations produced with and without their tools.

On the other hand, they do provide quantitative observations of physical errors made by animators without the use of the author's tools. These observations help separate instances where their tool is likely superfluous from those where it could significantly improve the physical accuracy of animations

Reproducibility The authors provide extensive detail on the mathematical basis of their ballistic path and angular momentum tools. Though the algorithms are relatively simple, they do provide pseudocode in figures. However, because the paper concerns tools provided to human users, the ease-of-use and clarity of the interface shown to the user by the tools is perhaps more important than the technical details; the complete UI system may be difficult to reproduce without more details.

Improvements

• The evaluation of the tools' effectiveness for animators is fairly vague; quantitative results or more controlled testing may have yielded more definite results.

• The angular momentum tool is only capable of modifying the root orientation of the character to correct the value; a more sophisticated system with the option of modifying character joint angles as well may have been useful when a character's rotation speed is fixed

-- BenHumberston - 17 Nov 2011