Guide to Using DWG and Other Formats
Guide to Using DWG and Other Formats
Guide to Using DWG and Other Formats

Issues That Affect IGES Export

This section covers issues concerning the exporting of a DGN file to IGES.

Excluding IGES entities

The breadth of the IGES specification makes it impractical for any receiving application to correctly interpret every IGES entity. Usually, you should exclude an entity that is not supported by the receiving application.

If you exclude an IGES entity listed in the section Alternate entities to use when exporting excluded IGES entities, the geometry that it represents is approximated with the corresponding alternate entity type. In most cases, the approximation is less compact and “intelligent” than the entity it replaces.

If an entity is not listed in the following table, its exclusion causes its geometry to be omitted from the IGES file.

The Exclude IGES Entities dialog box lets you exclude IGES entities. You can open the Exclude IGES Entities dialog box by choosing Settings > Exclude IGES Entities… from the menu bar of the Export IGES File dialog box.

Examples include the following:

Alternate entities to use when exporting excluded IGES entities

Unless the alternate entity is also excluded, the alternate entities for excluded IGES entities are as follows:

IGES Entity

Alternate If Excluded

100. Circular Arc

126. Rational B-spline Curve

102. Composite Curve

Individual component entities

104. Conic Arc

126. Rational B-spline Curve

106. Copious Data

110. Line(s)

108. Plane (Bounded)

230. Sectioned Area

116. Point

110. Line (zero length)

126. Rational B-spline Curve

106. Copious Data

128. Rational B-spline Surface

126. Rational B-spline Curves (rule lines)

142. Curve On Surface

B-spline Surface boundaries are ignored

144. Trimmed Surface

Grouped holes are exported as Sectioned Area entities (type 230)

212. General Note

106. Copious Data

230. Sectioned Area

Bounding elements area pattern

308. Subfigure Definition

Individual component entities

314. Color Definition

Standard colors are used

408. Singular Subfigure Instance

All cells are dropped (placed as individual entities in the IGES file)

If an element does not appear in the table, its exclusion causes its geometry to be omitted from the IGES file.