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Home > Supported File Formats > DirectX to OBJ


How to convert DirectX (.x) to OBJ (Wavefront .obj,.mtl)?


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.

     

DirectX

.x files are the native 3D file format of the legacy Microsoft DirectX v2/v3 API and 3D toolkit. They were generally associated with 3D gaming whereby low polygon meshes with skinning (deformation) and "animation sets/clips" were the required norm. At the time of its introduction in 1995 there really wasn't any other similar 3D file formats which supported these capabilities in one, well defined and easily accessible format. Direct3D shipped for the first time in the DirectX 2.0 SDK in June 1996

Historically, the DirectX technology was developed a company called Rendermorphics of the UK which Microsoft purchased in February 1995. As little known history, 3 companies in the UK developed advanced realtime rendering toolkits prior to 1995: Argonaut Software (BRender), Criterion Software (RenderWare) and Rendermorphics (Reality Lab). Microsoft was to license the Argonaut 3D toolkit but opted to purchase the entire Rendermorphics company instead, at the last moment. As these various toolkits often sold for $50k at that time, the other two competitors eventually went out of business once Microsoft started giving DirectX away for free.

Okino knows of the .x file format well as it was the first company to properly and fully implement a DirectX importer and exporter, including full support for skinning and animation at a time when no other software provided such conversion support.

The DirectX file format had a long life until some people inside and outside of Microsoft started to push the FBX file format instead.

     

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.