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[ink] pen rotation axis has undefined origin

From: Al Gilman <Alfred.S.Gilman@IEEE.org>
Date: Mon, 18 Dec 2006 21:07:51 -0500
Message-Id: <p06110429c1ace50ff33e@[]>
To: www-multimodal@w3.org


Your solid geometry was doing fine in defining the pen attitude coordinates
until you came to pen rotation.

Figure 3b shows the Rotation of the pen along its longitudinal axis.

There needs to be a definition of what the orientation of the pen is
when this coordinate is zero; the origin of the angular measure that
gets reported.

One possible definition is as follows:

The departure of a reference mark or meridian on the pen barrel from
the nominal 'up' direction which may be constructed by a ray
perpendicular to the pen barrel (somewhere not at the tip) and
intersecting a pure-Z ray arising from the tip. This angle is
measured in a clockwise direction when viewing the pen barrel from
tail to tip, in degrees.

This definition would relate well to the force distribution across
the two sides of a fountain pen nib.

A different way to identify the nominal 'up' direction would be the
plane passing through the pen barrel and a pure-Y ray passing through
the tip. Here the 'up' direction is a direction that has negative
correlation with the Y axis, which normally flows down.

This definition would relate well to the use of an x-acto art knife,
indictating the user's intent as to whether the next bit of the trace
should be increasing or decreasing in X coordinate.

Each of these example definitions is just a quick blurt; you can say
it more simply but you have to say something more than you have said.

Received on Tuesday, 19 December 2006 02:08:49 UTC

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