Efficient dynamic constraints for animating articulated figures.

E Kokkevis; D Metaxas

doi:10.1023/a:1009778128601

Home/Archive/PubMed

PubMed · 12194179

Efficient dynamic constraints for animating articulated figures.

E Kokkevis·D Metaxas

View original source ↗Export metadata ↓

Abstract

This paper presents an efficient dynamics-based computer animation system for simulating and controlling the motion of articulated figures. A non-trivial extension of Featherstone's O(n) recursive forward dynamics algorithm is derived which allows enforcing one or more constraints on the animated figures. We demonstrate how the constraint force evaluation algorithm we have developed makes it possible to simulate collisions between articulated figures, to compute the results of impulsive forces, to enforce joint limits, to model closed kinematic loops, and to robustly control motion at interactive rates. Particular care has been taken to make the algorithm not only fast, but also easy to implement and use. To better illustrate how the constraint force evaluation algorithm works, we provide pseudocode for its major components. Additionally, we analyze its computational complexity and finally we present examples demonstrating how our system has been used to generate interactive, physically correct complex motion with small user effort.

Explore related subjects

Acceleration Algorithms Biomechanical Phenomena Computer Graphics Computer Simulation Humans Imaging, Three-Dimensional Joints Locomotion Models, Anatomic NASA Discipline Space Human Factors Non-NASA Center Journal Article

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

E Kokkevis, D Metaxas. 1998. Efficient dynamic constraints for animating articulated figures.. https://doi.org/10.1023/a%3A1009778128601

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

The role of attention in horizontal curves: a comparison of advance warning, delineation, and road marking treatments.

Horizontal curves have been recognized as a significant safety issue for many years, a more important factor than road width or sight distance. The research literature suggests that driver errors associated with horizontal curves result from three inter-related problems: failures of driver attention, misperceptions of speed and curvature, and poor lane positioning. To examine the roles of attentional, perceptual, and lane placement factors in driver behaviour at curves, two groups of curve treatments were identified for testing with a driving simulator. The first group of treatments consisted of four combinations of warning signs designed to alert drivers to the presence of curves and produce a reduction in curve approach speeds. The second group was comprised of several types of road markings designed to affect drivers' speed and lane position as they drove through curves. The results indicated that advance warning signs by themselves were not as effective at reducing speeds as when they were used in conjunction with chevron sight boards and/or repeater arrows. Of the road marking treatments only rumble strips produced any appreciable reductions in speed. A herringbones road marking was found to produce significant improvements in drivers' lane positions, effectively flattening the drivers' paths through the curves. A treatment combining the herringbones treatment with chevron and repeater arrow signs produced both a reliable reduction in speed as well as improved lane positions. The results are interpreted as evidence that treatments that highlight perceptual cues are the most effective means of moderating drivers' curve speeds.

Acceleration↗

PubMed2007

Uppsalator's acceleration.

Semiquantitative prediction of the Uppsalator (electroosmotical oscillator developed in Uppsala) under constant voltage is confirmed via numerical solution of exact nonlinear integro-differential equations in partial derivatives (PDE). Critical voltage and characteristic features of pressure and liquid flow velocity as functions of time are reproduced with high precision. In particular, the number of inflection points per period of oscillating velocity increases with growing voltage from two to six. A new feature is demonstrated. For sufficiently high voltages the Uppsalator shows normal deceleration, i.e., the oscillation period grows with voltage. However, in some supercritical range of voltages, acceleration is observed, as expressed by decrease of the oscillation period with growing voltage. Thus, the Uppsalator at constant voltage considered earlier as an impossible phenomenon represents a great challenge for experimental verification.

Acceleration↗

PubMed2007

Photodissociation at 193 nm of some singly protonated peptides and proteins with m/z 2000-9000 using a tandem time-of-flight mass spectrometer equipped with a second source for delayed extraction/post-acceleration of product ions.

A tandem time-of-flight mass spectrometer was built for photodissociation (PD) of singly protonated peptides and small proteins generated by matrix-assisted laser desorption/ionization. PD was performed in a second source after deceleration of precursor ions. The delayed extraction/post-acceleration scheme was used for the product ions. For the PD at 193 nm of small singly protonated peptides, the present instrument showed much better sensitivity and resolution for product ions than the previous one (Moon JH, Yoon SH, Kim MS, Bull. Korean Chem. Soc. 2005; 26: 763) even though the overall spectral patterns obtained with the two instruments were similar. The present instrument was inferior in precursor ion selection and background noise level. PD was achieved for precursor ions as large as the singly protonated ubiquitin (m/z 8560.63), indicating that the photoexcitation is capable of supplying a sufficient amount of internal energy to dissociate large singly protonated proteins. As the precursor ion m/z increased, however, product ion signals deteriorated rather rapidly. As in the PD of small peptide ions with m/z around 1000, the types of the product ions generated from singly protonated peptides with m/z in the range 2000-4000 were mostly determined by the positions of arginine residues. Namely, a(n) and d(n) ions dominated when an arginine residue(s) was near the N-terminus while v(n), w(n), x(n) and y(n) dominated when the same residue(s) was near the C-terminus. In addition, d(n), v(n) and w(n) ions were generated according to the correlation rules previously observed in the collisionally activated dissociation. Isoleucine and leucine isomers could be easily distinguished based on the w(n) and d(n) ions.

Acceleration↗