XML Forms Data Format (XFDF) Specification - Adobe Partners

Appendix: XFDF Definitions for Comments on 3D or Rich Media Annotations
XML Forms Data Format Specification Perpendicular Dimension Related Elements 124
In the above figure, red items are the measure markup and black items are parameters. All markup items
are drawn on the Annotation Plane (AP). The text layout is defined in the similar manner as for linear
dimensions. The lower left corner of the text box is positioned at the Text Anchor Point (TP) and the text’s X
axis is aligned with the measure line and the text flows in the direction defined by a vector from Anchor
Point 1 (A1) to Anchor Point 2 (A2). The text’s up direction is defined as the cross product of the annotation
plane normal and the text X axis, in the direction defined by the TY parameter.
In addition to controlling text position, the Text Anchor Point (TP) also controls the lengths of leader lines
and the placement of the measure line. Since leader lines are parallel and the measure line must be
perpendicular to both leader lines, the intersection of leader lines and the measure line is easily computed.
If the text position TP is outside the area between A1 and A2, an extension line collinear to the measure
line connecting TP to the closest anchor point is generated.
There are three parts to the text string displayed with the measurement; a numeric value, a units string,
and an optional user string. The display of the numeric value field number is also controlled by the
precision value, which indicates how many digits to the right of the decimal point should be displayed.
The viewer can convert the numeric value to a string and combine it with the units string and user text as
appropriate.
The following is an example of a perpendicular measurement.
Measurement1
-1.000000 -0.000000 -0.000000
-0.051400 0.000000 0.000000
Base
-0.051400 -0.152400 0.000000
0.000000 -0.000000 -1.000000
-0.051400 -0.057428 -0.017686
-0.000000 -0.000000 1.000000
20.000000
0.000000 1.000000 0.000000
0.152400
cm
3