Adobe Acrobat SDK
Multimedia Features (Chapter 9 in PDF Reference)
Adobe® Supplement to the ISO 32000
9.5.6 Persistence of 3D Measurements and Markups 70
The key geometric parameters for an angular dimension are shown here.
FIGURE 9.23
The angle is defined by the measurement value
V
(30 in the
FIGURE 9.23
) and is the angle between the
leader direction vectors (
D1
and
D2
). The angular measurement markup is generated by first computing
the center point of the angle, cp in this figure.
The text position (
TP
) controls the position of the measurement text, the placement of the angle arc, and
the length and direction of the extension lines. The extension lines are drawn from the anchor point to a
point at a distance ||
TP
-cp|| from the center point cp along the associated direction vector, which is the
intersection of the angle arc and the extension line. The angle arc center is at the center point cp (and its
radius is ||
TP
- cp||) and is drawn between the two extensions lines. The markup text is displayed (based on
the text orientation parameters) with the lower-left corner of the text string starting at the text position
(
TP
).
The text layout is defined in a similar manner as for other dimensions. The lower-left corner of the text box
is positioned at the text anchor point (
TP
), and the text's X-axis is defined by the vector
TX
. Note that the
vector
TX
is expected to be orthogonal with the annotation plane normal. 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.
The measurement value is interpreted as either being in degrees or radians as defined by the (
DR
) value,
and the appropriate label string is created.
There are three parts to the text string displayed with the measurement: a numeric value (
V
), a degrees or
radians string (
U
), and an optional user string (
UT
). The display of the numeric value field number is also
controlled by the precision value (
P
), which indicates how many digits to display to the right of the decimal
point. The viewer should convert the numeric value to a string and combine it with the degrees or radians
string and user text as appropriate. This process is viewer dependent.
There are some special cases:
●
Parallel direction vectors (
D1
and
D2
) are invalid, and no markup is generated.
●
If the text position
TP
is outside the cone of the angle, an extension line is added to connect the text
with the angle arc.
$EG
$
!
!
40
$
CP
6ALUE
40
48
!0ANNOTATIONPLANENORMAL
49
