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A COMPARISON AND EVALUATION OF MOTION INDEXING ...

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separate files to describe motion is beneficial in a way that we can have multiple AMC<br />

files for a single ASF file in a single motion capture session.<br />

The Acclaim Skeleton Format (ASF) has an extension of .asf and describes<br />

the joints and the skeleton hierarchy. In this file format, lines beginning with a<br />

hash sign (#) are comments. The .asf file is divided into sections and each section<br />

starts with a keyword. All keywords in the file start with a colon character ”:”.<br />

The “:version” keyword describes the version of the skeleton definition. The “:name”<br />

keyword denotes the name of the skeleton to be used. The “:units” keyword describes<br />

a definition for all values and units of measure used. The “:documentation” section<br />

has documentation information which remains from one file creation to the next. The<br />

“:root” section describes the parent of the hierarchy. The “:bonedata” keyword starts<br />

a block that describes all of the remaining bones in the hierarchy.<br />

Each bone is enclosed within a “begin” and “end” pair of keywords and has the<br />

following information:<br />

• ”id”: A unique ID number for each segment.<br />

• ”name”: The unique name to each segment. Figure 1.1 shows the bone names<br />

and ids for a skeleton.<br />

• ”direction”: The direction of the bone which explains how to draw the segment<br />

with respect to the parent segment.<br />

• ”length”: The length of the bone which, combined with direction, gives the<br />

offset of the bone.<br />

• ”axis”: The global orientation of an axis vector. The token letters “xyz” de-<br />

scribe the order of rotations.<br />

• ”dof”: The possible degrees of freedom in the bone. The possible values are<br />

tx, ty, tz, rx, ry, rz, and l. Each of these tokens are channels appearing in the<br />

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