.svg)
An OBJ file is an open 3D exchange format and OBJ format for mesh geometries. It stores points, edges and triangular or polygonal faces, as well as optional material and texture references via MTL files. However, it does not contain semantic BIM attributes.
Why is the OBJ file important?
- Interoperability: Broad support in CAD, 3D printing, visualization and game engines.
- Visual quality: Supports UV coordinates, materials and textures for realistic representations.
- Bridge from scans and models: Suitable for transferring data from point cloud or scan meshing, or for use in viewers and AR.
How to work with OBJ files in practice
- Source/creation: Create a mesh from a point cloud through meshing, or export it from CAD, BIM or modeling tools and save it as a Wavefront OBJ.
- Structure/assets: Ideally, every OBJ file should include an MTL file for material definitions and textures such as PNG or JPG files. Keep paths consistent.
- Cleanup: Remove non-manifold edges, holes and duplicates; align normals; use decimation or retopology to improve file size and performance.
- Scale/coordinates: Define units such as m or mm and set the origin. For GIS or BIM use cases, use a local coordinate system if needed.
- Export/sharing: Deliver the complete package, including OBJ, MTL and textures. Alternatively, convert the file to glTF/GLB for better web and viewer performance.
OBJ file vs. STL/PLY/IFC
- OBJ: Mesh plus materials and textures, well suited for visualization and web viewers.
- STL: Pure triangular mesh without colors or materials; a standard format in 3D printing.
- PLY: Mesh or point cloud with support for colors and attributes; often used in research and scanner-related workflows.
- IFC: BIM exchange format with geometry AND semantic attributes/relationships, used for planning and operation.
Common mistakes and misunderstandings
- Missing MTL files/textures: Leads to grey models; check paths and relative linking.
- Unclear units: Confusing m and mm scales models incorrectly.
- Too many polygons: Makes viewers slow; use decimation or LOD.
- Incorrect normals/backface culling: Black surfaces in the viewer; recalculate normals.
- Confusion with BIM: OBJ usually does not contain component classes or property sets.
FAQ
How do I deliver a complete OBJ file?
Always include the MTL file and all textures such as PNG or JPG files in the same package or folder. Keep paths relative, use consistent file names and open/test the OBJ file.
What is OBJ better at than STL?
OBJ is better for visualization, web and AR because it supports materials and UV textures. For 3D printing, STL is often more robust because it is simpler.
How large can an OBJ file be?
As small as possible while maintaining sufficient quality: close holes, calculate normals, decimate the polygon count and, if needed, convert the file to glTF/GLB.