OBJ (or .OBJ) is a geometry definition file format first developed by Wavefront Technologies for its Advanced Visualizer animation package. The file has been adopted by many 3D graphics application vendors.
The OBJ file format is a simple data-format that represents 3D geometry alone — namely, the position of each vertex, the UV position of each texture coordinate vertex, vertex normals, and the faces that make each polygon defined as a list of vertices, and texture vertices. Vertices are stored in a counter-clockwise order by default, making explicit declaration of face normals unnecessary. OBJ coordinates have no units, but OBJ files can contain scale information in a human readable comment line.
STEP or "Standard for the Exchange of Product model data" is also referred as ISO 10303. STEP has been initially designed with the idea to supersede the IGES format (which was the first broadly used vendor-neutral CAD file format). However even today both formats co-exist and data in IGES and STEP represent lion share of all CAD files.
Typically, STEP can be used to exchange data between CAD, CAM, CAE, PDM/enterprise data modeling and other CAx systems. STEP addresses product data from mechanical and electrical design, geometric dimensioning and tolerancing, analysis and manufacturing, as well as additional information specific to various industries such as automotive, aerospace, building construction, ship, oil and gas, process plants and others.
STEP is developed and maintained by the ISO technical committee. There are also various technical groups that define usage conventions and recommended practices to ensure better interoperability between software applications. In CAD world, the most prominent group is www.cax-if.org that unites software vendors and industrial users.
ISO10303 is very extremely large and complex and is structured in multiple layers, for example, from physical file format definition (Part 21) to geometrical/topological definitions (Part 42), up to Application Protocols (AP’s) defining higher-level industry use cases. CAD Exchanger supports AP203, A214 and AP242, which are most commonly used AP's.
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