# IGES Writer

## Supported Entities

Entities supported by the IGES writer.
• Subfigure Definition (308)
• Singular Subfigure Instance (408)
• Composite curve (102)
• Plane (108)
• Line (110)
• Point (116)
• Rational B-spline curve (126)
• Rational B-spline surface (128)
• Curve on a parametric surface (142)
• Trimmed (parametric) surface (144)
• Form 7 group without back pointers (402)
• Transformation Matrix (124)
• Name Property (406 Form 15)
• Color Definition (314)

Fixed points (those associated with lines or surfaces) are not supported by the IGES standard and are not exported. In order to export fixed points, it is necessary to convert them to free points. Then, after import, those free points must be projected onto the appropriate lines or surfaces in order to generate fixed points with the proper association.

## Export Options

When IGES data is exported, it writes lines in a form resembling the database. Each segment on the line becomes a separate curve in IGES. If there is more than one segment in the line, the resulting curves in IGES are joined together with a composite curve entity. NURBS curves and ellipses are written as rational b-spline curves (IGES's rational B-splines are general NURBS).

Surface faces that comprise each surface are written to allow for output type options. NURBS surfaces are output as rational B-spline surfaces in IGES are cones, spheres, and tori. If necessary, curves on parametric surfaces and trimmed surface entities are used to trim the NURBS surface.

The IGES writer uses the iges_writer.ini file with the following available options:
@AssemblyMode
Value Description
Parts Create subfigure definition entity (308) and singular subfigure instance entity (408) from the part entity (default).
Assemblies Create subfigure definition entity (308) and singular subfigure instance entity (408) from the assembly entity.
Layers Send each component as a different layer (level) in the IGES file. This is the most efficient format.
Groups Send each component as an associative instance entity (type 402, form 7).
LayersAndGroups Send each component as a different layer (level), and send each set of faces comprising one surface as an associativity instance (group).
@AuthorName
Value Description
string String to write in the IGES author name field.

Default is Unknown.

@AuthorOrganization
Value Description
string String to write in the IGES author organization field.

Default is Unknown.

@Export
Value Description
All Export all geometry (default).
Displayed Export displayed geometry only.
@NameFromRepresentation
Value Description
on Assign part name in CAD file from the representation file name and attach it to the part entity.

Meaningful only if AssemblyMode = "Parts".

off Assign part name in CAD file from the part entity name in Engineering Solutions.

Meaningful only if AssemblyMode = "Parts".

@OptimizeForCAD
Value Description
on Fix gaps between stitched edges and vertices to make the actual geometry of the surfaces consistent with the model topology before export, and check the topology of the model for gaps that are larger than a given tolerance between shared, non-manifold, or suppressed edges. If the gap is found to be bigger than the tolerance, the surface and edge geometries are morphed parametrically and in 3D, if necessary, to make the gap smaller than the tolerance. In addition, non-essential degenerate edges are removed. This also modifies the geometry within Engineering Solutions (default).
off Do not perform the optimization steps.
@OuterLoop
Value Description
Optional1 The IGES 6.0 standard allows you to default to the natural outer loop of the surface being trimmed. If you are trimming a NURBS surface with several holes and no exterior trimming, the outer loop can be left out of the IGES file, making the surface representation shorter and more accurate. Use this option if it is supported by your IGES post-processor (default). This is not available with the JAMA-IS standard.
Mandatory2 For those post-processors that do not allow an optional outer loop, this option forces an outer loop to be written for trimmed surfaces.
@SourceUnits
Value Description
• MKS (m kg N s)
• MMKS (mm kg N s)
• MPA (mm t N s)
• CGS (cm g dyn s)
• MMKNMS (mm kg kN ms)
• MMGNMS (mm g N ms)
• IPS Std (in pounds lbf s)
• IPS Grav (in slinch lbf s)
• FPS Std (ft pounds lbf s)
• FPS Grav (ft slug lbf s)
Assign unit system to the data present in Engineering Solutions during export.
@TargetUnits
Value Description
• Microns
• Millimeters
• Centimeters
• Meters
• Kilometers
• Microinches
• Mils
• Inches
• Feet
• Miles
Units system written in the IGES file.
1. The most efficient form is JAMA planes and the Outer Loop Optional option; however, this choice may cause compatibility difficulties.
2. To be JAMA-IS compatible, select the JAMA planes and the Outer Loop Mandatory options.