Hatch pattern and DXF codes
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By Gopinath Taget

http://adndevblog.typepad.com/autocad/2013/01/hatch-pattern-and-dxf-codes.html

You might wonder what the correlation is between the definition file of a hatch pattern(acad.pat, acadiso.pat) and the
DXF codes of AcDbHatch object.

The following is dxf code for pattern data:

53 Pattern line angle
43 Pattern line base point, X component
44 Pattern line base point, Y component
45 Pattern line offset, X component
46 Pattern line offset, Y component
79 Number of dash length items
49 Dash length (multiple entries)

But you might observe that the values of the pattern in the DXF is not always the same as they are defined in the PAT
file. This is because the pattern values like base point and offset are transformed by parameters like pattern angle.
For instance:

Pattern line offset, X and Y component :

Take the values from the pattern file and rotate them around the z-axis with the pattern angle and you will be able to
figure out the value written in the DXF file. For example, from AR-CONC in acadiso.pat, the x and y offset is 104.896,
-149.807. Draw a line from 0,0, to 104.896,-149.807 and rotate it about 50 degrees. List its values and you will see
that the line is located at 182.185,-15.9391,0. The base point for rotation is 0,0. If you use the offset value from
DXF file 7.172601826007534,-0.6275213498259511 to draw a line starting at 0,0, you will see this line laps over the line
starting at 0,0 and ending at 182.185,-15.9391.
