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How to convert OBJ (Wavefront .obj,.mtl) to DWG (AutoCAD, DXF)?

PolyTrans|CAD+DCC performs mathematically precise CAD, DCC/Animation, GIS and BIM 3D file conversions into all key downstream 3D packages and file formats. Okino software is used and trusted throughout the world by many tens of thousands of 3D professionals in mission & production critical environments, backed by respectable personal support directly from our core development team.

OBJ

Wavefront OBJ is a little understood but highly used and prevalent 3D "polygonal mesh" file format used throughout the 3D graphics world. Okino, Alias Research and McNeel made it popular in the early to mid 1990s as a general purpose, simple-to-read, storage and transmission 3D file format, especially for the then-new companies who began to sell 3D mesh models via the Internet.

Relatively speaking, OBJ is a rather simple file format but a bit better than STL although similar to the more modern 3MF format.The OBJ format allows for 1 or more unique polygonal mesh objects to be defined, each with optional UV texture coordinates and vertex colors. Material definitions can be linked to the mesh geometry as defined in the separate 'MTL' file. The material definitions are rather simple (ie. no PBR material support) but acceptable, and with varied levels of texture mapping support. OBJ format does not provide support for object hierarchy, local transformations, meta data, lights, cameras, skinning or animation. Most notably, OBJ does not allow for 'object instancing' and hence 1000 copies of a screw would be saved to OBJ as 1000 explicit copies, rather than 1000 references to one master object.

A short history: In the 1980s there was a program called Wavefront Visualizer which ran on UNIX and ran its early rendering pipeline as a series of tee'd command line 'applets'. The data flowed from one applet to another via various ASCII based files - OBJ for geometry, MTL for materials and other ASCII files for animation, skinning, deformation, etc.

Okino knows of the Wavefront OBJ file very well as it provides the one and only full implementation of the OBJ file format and with the ability to consume exceedingly large OBJ files quickly and efficiently. This includes the only known implementation of OBJ-centric 'NURBS geometry' (surfaces and curves) within the OBJ file format (which is little or not used) other than that from the McNeel Rhino-3D software.

DWG

DXF and DWG are the native file formats of the Autodesk AutoCAD product since 1982. DWG is the binary file variation to the ASCII DXF file format. These files can be viewed by many programs including Autodesk's free DWG TrueView application. It is a closed file format but has been documented by the Open Design Alliance.

At Okino we consider DXF/DWG to be one of the worst 3D file formats when translating 3D model data between applications (depending on its contents). There is very little understanding about this in the 3D graphics world. As outlined in our "CAD Data Sourcing Suggestons and Rules" page you should ideally use the DWF-3D file format when sourcing from either AutoCAD, Navisworks, Revit and optionally Autodesk Inventor.

Due to deep history, Autodesk software can embed ACIS SAT "BREP solids" data in some of its DXF/DWG files. This is the ideal case as the "BREP solids" geometry definitions lead to cleaner and higher fidelity MCAD file conversions. But even so, it would generally be a safer bet to use a STEP AP214 or "IGES BREP solids" file in such cases.

OBJ import converter's overview

DWG export converter's overview