Computer-Based Animation of an Articulated Body

The fields investigated to provide the background of this work are Animation, Gait Research, Data Gathering and Simulation. A methodology for modelling quadruped gaits and gait transitions based on Fourier series analysis of horse movement is proposed. The methodology has been used to define a generic ro­toscoped model for movement, which although developed from horse movement data, could be equally applied to any other quadruped. The resultant model is used to create animated locomotion sequences of a quadruped changing gait. During locomotion the legs of an animal undergo a series of cyclic phases con­sisting of stance (foot-ground contact) and swing (foot moving to next ground location). When considering an animal as a whole the combination of leg move­ments for the animal constitute a gait. A gait can be characterised by the footfall pattern of the animal, the phase difference between the feet and the duty factor (percentage of ground contact during a leg cycle). Animation provides techniques to model the visual motion of a multi-legged figure moving using a number of different gaits, the control of movement is determined by the locomotion model. The locomotion model is based upon Fourier analysis of horse movement data and was chosen because of its ability to reduce the number of free parameters and filter noise from the input data, the resultant Fourier coefficients represent the amplitudes of the underlying frequencies of motion. Furthermore as locomotion is cyclic, the Fourier series is ideally suited to represent this cyclic nature. The dynamic similarity hypothesis allows the gaits of animals with similar limb arrangements to be compared. Gait changes occur at similar levels of a dimension­less parameter called the Froude number, which can be calculated from velocity, gravity and length characteristic for the animal. To change from one gait to another, there has to be some trigger to force the gait to change. In nature, the primary method for forcing a gait change is energy expenditure during locomotion. The gait transition model uses the change in Froude number as a trigger for the transition. The transition is modelled by blending from the Fourier series for a joint in one gait to the Fourier series for the same joint in another gait. This work proposes a methodology for modelling the locomotion of a quadruped moving using a single gait and a method for simulating a transition between two modelled gaits. The resultant animation proves that this is a viable approach. Valuable future research would be to refine both the locomotion and gait transi­tion models and extend them to animate other quadrupeds.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

De Montfort University

Year dc:date.issued

2000

Author dc:creator

• Mistry, Rajesh

Licence

• https://dora.dmu.ac.uk/bitstreams/fc20626a-00f9-4773-9d9e-c97b3f04caed/download