MIL-STD-2301A
5.1.1.5.5 Elliptical Arc element input. The CGM implementation for NITFS shall provide the capability to input and interpret the Elliptical Arc element using the following format. A conjugate diameter pair of an ellipse is a pair of diameters of the ellipse such that a tangent to the ellipse at each endpoint is parallel to the other
diameter. The centerpoint (CenterX, CenterY) specifies the center of an ellipse. The conjugate diameter endpoints (End1X, End1Y, and End2X, End2Y) include one endpoint from each conjugate diameter; together with the centerpoint they define the two conjugate diameters of the ellipse. StartVectorX and StartVectorY define a start vector, and EndVectorX and EndVectorY define an end vector. The tails of these vectors are placed on the centerpoint. A start ray and end ray are derived from the start and end vectors. The start and end rays are the
semi-infinite lines from the centerpoint in the direction of the start and end vectors respectively. The define arc begins at the intersection of the ellipse and the end ray in the direction defined as follows. A "conjugate radius" is defined to be half of a conjugate diameter. Letting the centerpoint be labeled M, the first conjugate diameter endpoint P1, and the second conjugate diameter endpoint P2, then the line segments M-P1 and M-P2 define two conjugate radii, referred to in what follows as the first conjugate radius and the second conjugate radius respectively. The conjugate radii meet at M and define two angles: the sum of the two angles is 360 degrees, one angle is less than 180 degrees and the other is greater than 180 degrees. The drawing direction of the elliptical arc is the direction from the first conjugate radius to the second conjugate radius through the smaller of these two angles. Valid values of the three specifying points of the ellipse are those which yield three distinct points. The specified ellipse is non-degenerate if and only if the three points are non-colinear. Valid values of the vector components are those which produce vectors of non-zero length. If the start ray and end ray are coincident, it is ambiguous whether the defined arc is null (zero arc length) or the entire ellipse. The arc width, type and color are specified by the Line Width, Line Type and Line Color commands, respectively.
TABLE LII. Elliptical Arc input.
MSB LSB
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
4 18 20 = 0x4254
CenterX CenterY End1X End1Y End2X End2Y StartVectorX StartVectorY End VectorX EndVectorY
5.1.1.5.6 Elliptical Arc Close element input. The CGM implementation for NITFS shall provide the capability to input and interpret the Elliptical Arc Close element using the following format. A conjugate diameter pair of an ellipse is a pair of diameters of the ellipse such that the tangent to the ellipse at each endpoint is parallel to the other diameter. The centerpoint (CenterX, CenterY) specifies the center of an ellipse. The conjugate diameter endpoints (End1X, End1Y, and End2X, End2Y) include one endpoint from each conjugate diameter; together with the centerpoint they define the two conjugate diameters of the ellipse. StartVectorX and
StartVectorY define a start vector, and EndVectorX and EndVectorY define an end vector. The tails of these vectors are placed on the centerpoint. A start ray and end ray are derived from the start and end vectors. The start and end rays are the semi-infinite lines from the centerpoint in the direction of the start and end vectors, respectively. The define arc begins at the intersection of the ellipse and the end ray in the direction defined as follows. A "conjugate radius" is defined to be half of a conjugate diameter. Letting the centerpoint be labeled M, the first conjugate diameter endpoint P1, and the second conjugate diameter endpoint P2, then the line segments M- P1 and M-P2 define two conjugate radii, referred to in what follows as the first conjugate radius and the second conjugate radius, respectively. The conjugate radii meet at M and define two angles: the sum of the two angles is
360 degrees, one angle is less than 180 degrees and the other is greater that 180 degrees. The drawing direction of the elliptical arc is the direction from the first conjugate radius to the second conjugate radius through the smaller of these two angles. Valid values of the three specifying points of the ellipse are those which yield three distinct points. The specified ellipse is non-degenerate if and only if the three points are non-colinear. Valid values of the
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