Sunday, May 15, 2016
AutoCAD DXF (Drawing Interchange Format, or Drawing Exchange Format) is a
CAD data file format developed by Autodesk[2] for enabling data
interoperability between AutoCAD and other programs.DXF was originally
introduced in December 1982 as part of AutoCAD 1.0, and was intended to
provide an exact representation of the data in the AutoCAD native file
format, DWG (Drawing), for which Autodesk for many years did not publish
specifications. Because of this, correct imports of DXF files have been
difficult. Autodesk now publishes the DXF specifications as a PDF[1] on
its website.Versions of AutoCAD from Release 10 (October 1988) and up
support both ASCII and binary forms of DXF. Earlier versions support
only ASCII.As AutoCAD has become more powerful, supporting more complex
object types, DXF has become less useful. Certain object types,
including ACIS solids and regions, are not documented. Other object
types, including AutoCAD 2006's dynamic blocks, and all of the objects
specific to the vertical market versions of AutoCAD, are partially
documented, but not well enough to allow other developers to support
them. For these reasons many CAD applications use the DWG format which
can be licensed from Autodesk or non-natively from the Open Design
Alliance.DXF coordinates are always without dimensions so that the
reader or user needs to know the drawing unit or has to extract it from
the textual comments in the sheets.Contents1 File structure2 See also3
References4 External linksFile structureASCII versions of DXF can be
read with any text editor. The basic organization of a DXF file is as
follows:[3]HEADER section – General information about the drawing. Each
parameter has a variable name and an associated value.CLASSES section –
Holds the information for application-defined classes whose instances
appear in the BLOCKS, ENTITIES, and OBJECTS sections of the database.
Generally does not provide sufficient information to allow
interoperability with other programs.TABLES section – This section
contains definitions of named items.Application ID (APPID) tableBlock
Record (BLOCK_RECORD) tableDimension Style (DIMSTYPE) tableLayer (LAYER)
tableLinetype (LTYPE) tableText style (STYLE) tableUser Coordinate
System (UCS) tableView (VIEW) tableViewport configuration (VPORT)
tableBLOCKS section – This section contains Block Definition entities
describing the entities comprising each Block in the drawing.ENTITIES
section – This section contains the drawing entities, including any
Block References.OBJECTS section – Contains the data that apply to
nongraphical objects, used by AutoLISP and ObjectARX
applications.THUMBNAILIMAGE section – Contains the preview image for the
DXF file.END OF FILEThe data format of a DXF is called a "tagged data"
format which "means that each data element in the file is preceded by an
integer number that is called a group code. A group code's value
indicates what type of data element follows. This value also indicates
the meaning of a data element for a given object (or record) type.
Virtually all user-specified information in a drawing file can be
represented in DXF format."[4]
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