AutoCAD DWG - Which format should I use?

Introduction

There are four formats in FME that can be used to read or write AutoCAD drawing files (.dwg or .dxf)

1. Autodesk AutoCAD DWG/DXF (ACAD)
2. Autodesk AutoCAD RealDWG DWG/DXF (REALDWG)
3. Autodesk AutoCAD Map 3D Object Data (AUTOCAD_OD)
4. Autodesk AutoCAD Civil 3D (CIVIL3D)

Note: This solution applies to AutoCAD drawing formats (.dwg and .dxf.) Autodesk DWF and SDF formats are not covered here and should be considered completely different formats.

We aim to support the latest version of AutoCAD applications. For best performance be sure that your version of FME is newer or the same as your version of AutoCAD. For example, if you are wanting to read a file created in AutoCAD 2020 then FME 2020 and higher is what you will want to use for the best results.
 

1. Autodesk AutoCAD DWG/DXF (ACAD)

The Autodesk AutoCAD DWG/DXF (ACAD) format is built-in FME using libraries from the Open Design Alliance. In addition to supporting standard AutoCAD entities, the ACAD format supports primitive 3D geometry reading and writing. Generally, 3D objects are decomposed into meshes and converted to composite surfaces. Solids are turned into surfaces, meshes are turned into less efficient surfaces, and textures are lost.

Note: Because the format uses libraries from the Open Design Alliance you may notice a warning message when opening a file created with this writer in AutoCAD about the file is not developed or licensed by Autodesk. This warning is not present when using the REALDWG writer (see below).

2. Autodesk AutoCAD RealDWG DWG/DXF (REALDWG)

The Autodesk AutoCAD RealDWG DWG/DXF (REALDWG) format is built-in FME using the REALDWG library provided by AutoDesk Inc. The REALDWG format supports more full 3D geometry reading and writing. Generally, surfaces are handled as meshes and solids as BREPs composed of mesh surfaces. Textures may be used, but only on subdivision meshes which may be a subset of the dataset to be read. Surfaces other than meshes that have textures in FME may be converted to subdivision meshes on write.

3. Autodesk AutoCAD Map 3D Object Data (AUTOCAD_OD)

The Autodesk AutoCAD Map 3D Object Data (AUTOCAD_OD) format is an extension of the REALDWG library above but intended for use when you want to read or write object data as used in Autodesk Map products. Otherwise, this format has the same 3D capabilities and the same platform limitations as the REALDWG format above.

4. Autodesk AutoCAD Civil 3D (CIVIL3D)

The Autodesk AutoCAD Civil 3D (CIVIL3D) format is primarily intended for use with the AutoDesk product CIVIL 3D. It extends the capability of drawing file reading to include entities that are specific to Civil 3D.
More details on this format and a complete list of supported and unsupported geometries and features can be found here: Autodesk_AutoCAD_Civil_3D

The CIVIL3D format (reader only) is supported on Windows (32 bit and 64 bit), Linux, and Mac.

To ensure you can read files created with Civil 3D be sure that the version of FME is the same or higher than that of the version of Civil 3D that was used to create the file.