Convert OBJ to SAT in your application
3D InterOp is a CAD interoperability SDK that lets your software read OBJ files and write SAT, writing the OBJ facets as faceted geometry, since OBJ stores triangles rather than solids.
Spatial does not offer an online converter or a desktop conversion app. 3D InterOp is a component that software vendors embed in their own products.
- Reads OBJ · Writes ACIS
- Triangle mesh → faceted B-Rep
- C++ / C# APIs
OBJ to SAT at a glance
OBJ stores triangles; ACIS is an exact-geometry format. The mesh is written as faceted geometry: 3D InterOp doesn’t rebuild smooth surfaces from triangles.
| OBJ (source) | ACIS (target) | |
|---|---|---|
| Full name | Wavefront OBJ | ACIS model file (text SAT, binary SAB) |
| Standard / owner | Open format | Proprietary — Spatial (Dassault Systèmes) |
| File extensions | .obj | .sat, .sab |
| Geometry | Polygon mesh | Exact B-Rep |
| Assemblies / structure | No assembly hierarchy | Parts in SAT/SAB, assemblies in ASAT/ASAB |
| 3D InterOp support | Read and write | Read and write · ACIS R18 to 2026 1.0 |
What's preserved, what changes
Here is what your application can expect to carry across from OBJ to ACIS.
-
Changes
Faceted geometryOBJ stores triangles, so the SAT file holds faceted bodies, not solids. 3D InterOp doesn’t rebuild exact B-Rep from a mesh.
Why software vendors add OBJ to SAT conversion
Hand models to kernel-based applications
Many CAD, CAM and CAE applications are built on the ACIS kernel. Writing ACIS gives them exact geometry they can load without another translation step.
Downstream modeling and analysis
An exact ACIS B-Rep can still be edited, meshed or machined by downstream tools, which a tessellated export would not allow.
Exchange within one ecosystem
Partners whose tools share the ACIS kernel often prefer to exchange ACIS files directly.
Things to check before you ship
- Written SAT versions: ACIS R18 to 2026 1.0.
- Supported OBJ input: any OBJ version.
- Validate a sample of translated files in the target system your users actually work with.
Working with Spatial was a real milestone for us: Thanks to the powerful 3DInterOp library, we were able to successfully bring our complex CAD-based solutions to the cloud while remaining flexible to meet individual customer requirements. For us, Spatial is not just a technology partner, but a true enabler of our product strategy.
Dr. Arno Michelis, Founder, Simus Systems
Read the Case StudyAbout the formats
-
Source format
What is an OBJ (.obj) file?
OBJ is a simple, widely supported text format for polygon meshes, created by Wavefront. It describes vertices, faces and texture coordinates, with materials in a separate .mtl file.
-
Target format
What is an ACIS SAT file?
SAT is the native file format of 3D ACIS Modeler, Spatial's geometric modeling kernel used in CAD, CAM and CAE applications. It stores exact B-Rep models as text (.sat) or binary (.sab); ACIS assemblies use the .asat and .asab extensions.
Frequently asked questions
No. OBJ stores triangles, and 3D InterOp writes them to SAT as faceted geometry. It doesn’t rebuild exact B-Rep from a mesh.
Not above degree 25: ACIS doesn’t support B-spline geometry with a higher degree, so such geometry may be missing from the SAT file.
Yes. 3D InterOp reads the visual material properties of OBJ files on import.
3D InterOp reads any OBJ version, as visualization data.
3D InterOp writes ACIS R18 to 2026 1.0.
Yes. 3D InterOp reads and writes both formats, so SAT to OBJ is supported too.
-
Building software that needs to convert OBJ to SAT?
3D InterOp is an SDK that lets your application read OBJ and write ACIS alongside 30+ CAD and BIM formats.