Introducing the New DGN Format in FME (Technical Preview)

Introduction

In FME 2026.4, we rebuilt the Bentley MicroStation DGN reader and writer from the ground up, which makes it much easier for us to add improvements and fix bugs. The new writer features a new data model and significant performance improvements when reading in files compared to the previous DGNv8 reader and writer.

In this article, you'll learn what changes when you move from the V8 format, how the new metadata feature types let you validate DGN files, and what else is new in the Technical Preview.

Look for Bentley MicroStation Design (DGN - Technical Preview) in the reader/writer gallery. The Bentley MicroStation Design (V8) format stays available while the new format is in Technical Preview, so your existing workspaces keep working.

Moving from the V8 Format

You can still do everything you did with V8, so we recommend using the new format in new workspaces. That said, the new reader and writer aren’t a drop-in replacement for the V8 ones, transferring existing workspaces will require users to make changes or rebuild the existing workspaces. We highly recommend switching to the new format when it is possible to take advantage of its improvements.

The main reason is that attribute names have changed. The igds_* prefix is now dgn_*, and most attributes have a direct successor:

Other changes to review:

• dgn_element_type holds a name, not a number: Line, not 3.
• Element type, model and level are no longer required on write. The writer infers the element type from the geometry, writes to the Default model and uses the default level. dgn_level_name takes precedence over dgn_level_number.
• Metadata features are identified by dgn_metadata_type, not dgn_element_type.
• Insertion point and rotation for cells and text now live in the geometry, where FME transformers can act on them, instead of in attributes (igds_insertion_x/_y/_z, igds_rotation, igds_quat.*, igds_start_angle, igds_sweep_angle). Cell scale is still an attribute.
• Level properties are attributes on Level Metadata features instead of fields on the writer feature type dialog.
• Dimensions and text nodes are no longer exploded by default, so workspaces built against the V8 defaults will receive whole dimensions and whole paragraphs.
• Text Nodes are built from MultiText geometry. If you author Text Nodes in FME rather than round-tripping them, your workflow changes.
• Apply World File now defaults to off. It defaulted to on in the V8 reader.
• Removed:
  • the Linkage Extraction parameter (user data linkages are now read as the generic User linkage type in the dgn_linkage{} list)
  • character encoding parameters
  • element bounding-range attributes (igds_xlow, igds_yhigh, etc.)
  • igds_element_modified
  • XFM / DgnStore support, including the DGNV8XFM format

New: Validate DGN Files with Metadata Feature Types

The new format exposes MicroStation's resource tables as FME feature types you can read, transform and write. That means you can validate design standards without opening MicroStation: check which levels are in use, which text styles differ from your corporate standard, or which files reference a line style that isn't embedded.

The same feature types work on write, so you can build a correctly styled DGN without a hand-built seed file. For example, generate levels from a spreadsheet, or pull a line style from one file and a text style from another into a new design file.

Other Format Improvements

• B-splines are written as real B-spline elements, and clothoids are written as B-splines instead of being flattened into polylines. Point Strings (type 22) are now read and written.
• The seed file is optional, and a v7 seed is accepted and upgraded to v8. Copy Seed File Elements and Purge Unused Elements control what's carried over from the seed.
• Cells stay intact. Read Cells As offers Geometry Instances (default), Expanded Features or Insertion Point Only. Turn on Read Additional Cell Libraries to read .cel and .dgnlib files from a folder. Shared cell definitions can be written.
• Dimensions arrive with their witness points and properties, and multilines (type 36) with their profiles. Both write back as native elements..
• Smart and parametric solids and surfaces are read as real solids. Meshes (type 105), materials and textures are read and written. On write, closed planar solids become Smart Solids and curved solids are written as meshes.
• Array Item Types become list attributes, nested properties are flattened to any depth, and Bentley's internal EC schemas are filtered out. Tags and Tag Sets come through as Item Types.
• Color tables round-trip, color books display correctly, and fme_color / fme_fill_color are honored on write.
• Features the writer can't write go to the FeatureWriter's <Rejected> port with a reason, instead of only logging a warning.
• xData is read as list attributes. xAttributes and linkages are read and written, along with element thickness, transparency, priority, graphics group and lock state.
• Symbology Resource Files (.rsc) resolves fonts and symbology to real names.
• Models to Read and Search Envelope limit what's read.

Updated Transformer: DGNStyler

The DGNStyler transformer has a new Format Compatibility Mode parameter. Leave it on DGNv8 to keep the existing behavior, or switch to DGN (Technology Preview) to write the new format's attributes. DGN mode adds these controls:

• Color Source: Value, By Level or By Cell
• Fill Type: No Fill or Fill Color
• Text Style Name: select a text style by name instead of numeric ID
• Italic, Underline Colour/Weight and Overline Colour/Weight
• Background with a fill color index
• Line Spacing Type: Exact, Automatic, From Line Top or At Least
• Is Annotation for annotation scaling
• Cell Type: Named From Library or Shared

Known gaps in DGN mode: there's no Cell Size By control (scale factor only), Fill Type is disabled when Color Source is By Level, and hex colors supplied through a user attribute aren't accepted.

Current Limitations

• Rasters, Donut and MultiArea geometry can't be written.
• Point, raster and compound line style components are still being refined.
• Text encoding on some files is handled better by the V8 reader.
• 3D text node rotation isn't correct in all cases yet.
• Complex chains and shapes lose some element properties on write.
• Italics and slant on written text nodes, and some text style color settings, are constrained by the underlying CAD libraries.

Additional Resources

Have Feedback or Running into Issues?

The new DGN format is in Technical Preview, so your feedback shapes it. If you have feedback or run into issues, please create a support ticket.