FME Creates Large AutoCAD DXF Files

Symptom

AutoCAD DXF files created by FME seem to be larger than those produced by other software packages.

Cause

The difference in size is caused by FME's default method of writing 3D polylines.

AutoCAD has 2D and 3D polylines which store their vertices as entities, and light-weight polylines which store vertices as coordinates only.

If the data is 3D with a constant z (elevation), other applications like Microstation export this as a lightweight polyline (a 2D object) with an elevation. However, FME writes all 3D lines as 3D polylines by default.

Resolution

In FME you can specify which specific AutoCAD entity type to write using autocad_original_entity_type. If you know that a line is planar, you can set autocad_entity_type to autocad_line, and autocad_original_entity_type to autocad_lwpolyline to create a light-weight polyline.

FME documentation contains a list of the AutoCAD entity types.