DXF and DWG File Formats

DXF and DWG are two common file formats used to exchange information between different CAD and drawing programs. DXF is a semi-public standard promoted and controlled by Autodesk, Inc. DWG is a proprietary, closed format used by Autodesk for its products. DXF and DWG files contain almost identical information, and both store all of the same objects. Recent versions of AutoCAD have bugs when reading some DXF files, such as losing links to images, so DWG is usually a safer choice in that case. As of this writing, the most recent DXF/DWG version is version 2007/2008.VectorWorks imports and exports versions 2.5 through 2007/2008. Export to versions earlier than 12 is not recommended; maximum file integrity cannot be maintained, because too much information is lost during the translation.

The following changes to the DXF/DWG translation procedure have been added:

Worksheet images can now be exported to DXF in a single step, without exporting a separate sheet and importing it into the DXF/DWG drawing. All cell formatting is now preserved, including: text font, size, style, color, and position inside the cell; cell border line style, thickness, and color; cell fills.

Importing from and exporting to DXF/DWG is not the same as saving or opening a VectorWorks file. It is a translation from one way of doing things to another; consequently, information can get lost in the translation. Following are some items that DXF/DWG handles differently. These can introduce unwanted effects in the translated file.

Item	Description
Units	Version 2000 DXF/DWG and later supports the concept of true units, so the file’s unit settings can be imported (if it includes units). Previous versions of DXF/DWG do not support units, and some version 2000 and later files may be unitless. There is no way for VectorWorks to tell whether these unitless drawings were made in meters, feet and inches, or microns. Communicate with the person providing the file to determine this information. Unitless DXF/DWG files do have five “units” settings (such as “Architectural” and “Engineering”) which are used to guess the original units, but the guess may need to be adjusted.
Line Weights	VectorWorks allows line weights and colors to be specified independently. AutoCAD has recently gained the ability to do so, but most AutoCAD users still use colors to map to line weights. Version 14 and earlier DXF/DWG files do not support true line weights at all. If you choose to export with line weights mapped to colors, then original object colors will be lost.
Colors and Fills	VectorWorks is more graphically rich than DXF/DWG can currently support. In all cases, VectorWorks chooses the closest possible translation given the limitations inherent in DXF/DWG. The default version in the export dialog box will always give the best results possible, assuming the recipient’s software can read all of the information. DXF/DWG versions prior to 2004 have a fixed color palette (which changes slightly depending on whether the background is black or white) and all objects have just one solid color associated with them. Objects such as circles in DXF have no fill color (just a line color). A few objects can have a fill color, but they have no separate line color. DXF/DWG version 14 and above supports a “solid hatch,” which is a separate object that can be associated with objects such as circles to make them look like they have a color fill. These hatches cannot be the same color as the background color (such as a white rectangle on a white background to mask objects underneath). Since these solid hatches can be associative, VectorWorks can import them and set the associated object’s fill color instead of having two separate objects for frame and fill. DXF/DWG version 2000 supports “wipeout” entities, which are essentially polygonal images filled with the background color. Some AutoCAD users may not want to receive files with wipeouts. DXF/DWG export includes an option to exclude solid fills (which includes both wipeouts and solid hatches). Since wipeouts can only be polygons and are not associative, if a white circle on a white background is exported and then re-imported into VectorWorks, the result is an unfilled circle and a polygon with a white fill and no pen inside the circle. The smoothness of the polygon (number of facets) depends on the 2D conversion resolution preference when it was exported. Objects with pattern fills, image fills, or gradients export as a plain solid color.
Layers and Classes	Each VectorWorks design layer is similar to a DXF/DWG model space. A VectorWorks drawing can have many design layers visible at the same time, with different scales and views for each design layer, but only one model space is allowed in a DXF/DWG file. Therefore, VectorWorks has to merge the multiple design layers, and some information can be lost. The drawing should generally look and print the same after the export, but independent layer scales, object coordinates, and invisible objects can be lost.
Groups and Symbols	VectorWorks uses symbols, which are objects that can be inserted multiple times without greatly increasing the file size, and which need only one edit to update all copies. It also has groups, which are objects that are grouped together and act as one object. The DXF/DWG equivalent of a VectorWorks symbol is called a “block.” The closest DXF/DWG equivalent to a VectorWorks group is an “anonymous block,” which is like a symbol without a name. Anonymous blocks cannot be edited easily in AutoCAD, however, so VectorWorks no longer exports anonymous blocks. Instead, if the plug-in object or group has a name assigned in the Data tab of the Object Info palette, then that name is used; otherwise a name is generated automatically.
Attributes and Linked Text	DXF/DWG does not have database records that correspond to VectorWorks record formats. It does have objects called attribute definitions (“attdefs”) which, when placed in blocks/symbols, behave somewhat like linked text in VectorWorks. The correspondence is very loose and as a result translation of these objects is not always smooth. DXF/DWG block attributes are created for things exporting as blocks (symbols, groups, plug-in objects, or layer links) that have record formats attached. Because only DXF/DWG blocks can have attributes attached, the record format information is not exported for other object types, such as lines or circles.
Names	When exporting to DXF/DWG version 2000 and later, the characters in layer and block names will not change. Accurate translation of lower case text, spaces and other Unicode characters is supported (except for the following illegal characters, which are converted during export: < > " `, / \ : ? * \| = ). Export to previous versions converts all name characters to uppercase; all spaces and special characters are converted to underscores. DXF/DWG attribute tag names cannot have spaces in any version; any spaces found in record field names are converted to an underscore.
Styled Multiline text	Multiline formatted text includes various sized fonts that are bold, underlined, or italicized, and that wrap to the next line. This type of text is supported for DXF/DWG versions 13 and up. For earlier versions, wrapped text is split into separate lines.
Layer Transfer Mode / Transparency	DXF/DWG does not support layer transfer modes or transparency, so use only paint transfer mode (100 percent opaque under Quartz and GDI+ imaging)
Dimensions	VectorWorks and AutoCAD handle dimensions, units, and dimension standards very differently. Dimensions exported to DXF/DWG look exactly the same when opened in AutoCAD, but they may change appearance slightly if edited. VectorWorks also creates appropriate dimension styles for all dimension standards that are used in the file, so even if the recipient modifies the dimensions or creates new ones, they should not look significantly different. During import, the file’s current units and dimension standard may be used, so imported dimensions may look slightly different. All common dimension styles should transfer flawlessly, but ensure that the VectorWorks file is set up with the correct units, angular units, dimension standard, and design layer page size before import. When doing a batch import of multiple files, choose an appropriate template file that has the appropriate settings. If unsure what the source file is using, use the import option to import the dimensions as groups, preserving the original look. It is recommended to import once as groups to evaluate the settings requirements, and then again as dimensions in a new file with the appropriate settings. If markers look too small or too large, the layer scale and page size may need to be adjusted.

Item

Description

Units

Version 2000 DXF/DWG and later supports the concept of true units, so the file’s unit settings can be imported (if it includes units). Previous versions of DXF/DWG do not support units, and some version 2000 and later files may be unitless. There is no way for VectorWorks to tell whether these unitless drawings were made in meters, feet and inches, or microns. Communicate with the person providing the file to determine this information. Unitless DXF/DWG files do have five “units” settings (such as “Architectural” and “Engineering”) which are used to guess the original units, but the guess may need to be adjusted.

Line Weights

VectorWorks allows line weights and colors to be specified independently. AutoCAD has recently gained the ability to do so, but most AutoCAD users still use colors to map to line weights. Version 14 and earlier DXF/DWG files do not support true line weights at all. If you choose to export with line weights mapped to colors, then original object colors will be lost.

Colors and Fills

VectorWorks is more graphically rich than DXF/DWG can currently support. In all cases, VectorWorks chooses the closest possible translation given the limitations inherent in DXF/DWG. The default version in the export dialog box will always give the best results possible, assuming the recipient’s software can read all of the information.

DXF/DWG versions prior to 2004 have a fixed color palette (which changes slightly depending on whether the background is black or white) and all objects have just one solid color associated with them. Objects such as circles in DXF have no fill color (just a line color). A few objects can have a fill color, but they have no separate line color.

DXF/DWG version 14 and above supports a “solid hatch,” which is a separate object that can be associated with objects such as circles to make them look like they have a color fill. These hatches cannot be the same color as the background color (such as a white rectangle on a white background to mask objects underneath). Since these solid hatches can be associative, VectorWorks can import them and set the associated object’s fill color instead of having two separate objects for frame and fill.

DXF/DWG version 2000 supports “wipeout” entities, which are essentially polygonal images filled with the background color. Some AutoCAD users may not want to receive files with wipeouts. DXF/DWG export includes an option to exclude solid fills (which includes both wipeouts and solid hatches). Since wipeouts can only be polygons and are not associative, if a white circle on a white background is exported and then re-imported into VectorWorks, the result is an unfilled circle and a polygon with a white fill and no pen inside the circle. The smoothness of the polygon (number of facets) depends on the 2D conversion resolution preference when it was exported.

Objects with pattern fills, image fills, or gradients export as a plain solid color.

Layers and Classes

Each VectorWorks design layer is similar to a DXF/DWG model space. A VectorWorks drawing can have many design layers visible at the same time, with different scales and views for each design layer, but only one model space is allowed in a DXF/DWG file. Therefore, VectorWorks has to merge the multiple design layers, and some information can be lost. The drawing should generally look and print the same after the export, but independent layer scales, object coordinates, and invisible objects can be lost.

Groups and Symbols

VectorWorks uses symbols, which are objects that can be inserted multiple times without greatly increasing the file size, and which need only one edit to update all copies. It also has groups, which are objects that are grouped together and act as one object. The DXF/DWG equivalent of a VectorWorks symbol is called a “block.” The closest DXF/DWG equivalent to a VectorWorks group is an “anonymous block,” which is like a symbol without a name. Anonymous blocks cannot be edited easily in AutoCAD, however, so VectorWorks no longer exports anonymous blocks. Instead, if the plug-in object or group has a name assigned in the Data tab of the Object Info palette, then that name is used; otherwise a name is generated automatically.

Attributes and Linked Text

DXF/DWG does not have database records that correspond to VectorWorks record formats. It does have objects called attribute definitions (“attdefs”) which, when placed in blocks/symbols, behave somewhat like linked text in VectorWorks. The correspondence is very loose and as a result translation of these objects is not always smooth. DXF/DWG block attributes are created for things exporting as blocks (symbols, groups, plug-in objects, or layer links) that have record formats attached. Because only DXF/DWG blocks can have attributes attached, the record format information is not exported for other object types, such as lines or circles.

Names

When exporting to DXF/DWG version 2000 and later, the characters in layer and block names will not change. Accurate translation of lower case text, spaces and other Unicode characters is supported (except for the following illegal characters, which are converted during export: < > " `, / \ : ? * | = ). Export to previous versions converts all name characters to uppercase; all spaces and special characters are converted to underscores. DXF/DWG attribute tag names cannot have spaces in any version; any spaces found in record field names are converted to an underscore.

Styled Multiline text

Multiline formatted text includes various sized fonts that are bold, underlined, or italicized, and that wrap to the next line. This type of text is supported for DXF/DWG versions 13 and up. For earlier versions, wrapped text is split into separate lines.

Layer Transfer Mode / Transparency

DXF/DWG does not support layer transfer modes or transparency, so use only paint transfer mode (100 percent opaque under Quartz and GDI+ imaging)

Dimensions

VectorWorks and AutoCAD handle dimensions, units, and dimension standards very differently. Dimensions exported to DXF/DWG look exactly the same when opened in AutoCAD, but they may change appearance slightly if edited. VectorWorks also creates appropriate dimension styles for all dimension standards that are used in the file, so even if the recipient modifies the dimensions or creates new ones, they should not look significantly different.

During import, the file’s current units and dimension standard may be used, so imported dimensions may look slightly different. All common dimension styles should transfer flawlessly, but ensure that the VectorWorks file is set up with the correct units, angular units, dimension standard, and design layer page size before import. When doing a batch import of multiple files, choose an appropriate template file that has the appropriate settings.

If unsure what the source file is using, use the import option to import the dimensions as groups, preserving the original look. It is recommended to import once as groups to evaluate the settings requirements, and then again as dimensions in a new file with the appropriate settings. If markers look too small or too large, the layer scale and page size may need to be adjusted.