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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@[192.168.1.100]>
To: www-multimodal@w3.org


Reference:
http://www.w3.org/TR/2006/WD-InkML-20061023

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

<quote
cite="">
Figure 3b shows the Rotation of the pen along its longitudinal axis.
</quote>

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.

Al
Received on Tuesday, 19 December 2006 02:08:49 GMT

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