Object String (.str) File Format Specification

Object strings are objects placed along a bezier curve. They are used primarily to build airport taxiway lights but can be used to place any kind of object desired.

Object string files are standard X-Plane 8 text files starting with a header and then commands. The # defines a comment.


Object strings are used by defining polygons in the DSF file. The polygon may have windings – only lat and lon coordinates are needed. The polygon parameter is used to indicate the spacing of objects in meters.

If two coordinates are provided (lon, lat) then the string is made of line segments. But if it is made of four coordinates (lon, lat, control lon, control lat) then it is interpretted as bezier curves.

The commands define the string of objects.

OFFSET <distance>

The offset command defines how far to the right of the line segment (as defined by traveling along the segment) the objects are to be placed. Positive numbers are to the right, negative to the left, and zero is right on the line.

OBJECT <random 1> <random 2> <object>

The object command specifies an object to put in the chain – all objects are alternated as the chain is laid out. Objects are placed heading along the chain plus a clockwise offset between random 1 and random2.

The object name can be the name of a library object, found in a different scenery package, or an object found relative to the .str file.

Example file:


OBJECT 0 inset_centerline_txy.obj
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