Convert JT to ASAT in your application
3D InterOp is a CAD interoperability SDK that lets your software read JT files and write ASAT, carrying across the exact geometry the JT file contains.
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 JT · Writes ACIS assembly
- Mixed geometry → exact geometry
- C++ / C# APIs
JT to ASAT at a glance
JT can mix exact solids and facets; ACIS assembly stores exact geometry. Exact elements are written as exact geometry, and elements stored only as facets stay faceted.
| JT (source) | ACIS assembly (target) | |
|---|---|---|
| Full name | Jupiter Tessellation | ACIS assembly, text (ASAT) and binary (ASAB) |
| Standard / owner | Siemens, ISO 14306 | Spatial (3D ACIS Modeler) |
| File extensions | .jt | .asat, .asab |
| Geometry | Tessellated and/or exact B-Rep | Exact B-Rep |
| Assemblies / structure | Yes | Yes |
| PMI | Semantic and graphical | Assembly-level PMI written as attributes |
| 3D InterOp support | Read only | Read and write |
What's preserved, what changes
Here is what your application can expect to carry across from JT to ACIS assembly.
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Preserved
Exact geometryExact B-Rep read from JT is written to ASAT as exact geometry.
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Preserved
Product structureThe JT product structure is written to ASAT.
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Changes
Faceted partsParts the JT file stores only as facets are written as facets.
Why software vendors add JT to ASAT conversion
Hand models to kernel-based applications
Many CAD, CAM and CAE applications are built on the ACIS assembly kernel. Writing ACIS assembly gives them exact geometry they can load without another translation step.
Downstream modeling and analysis
An exact ACIS assembly 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 assembly kernel often prefer to exchange ACIS assembly files directly.
Things to check before you ship
- Written ASAT versions: ACIS R18 to 2026 1.0.
- Supported JT input: JT 8.x to 10.3 and 10.5 to 10.11.
- 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
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Source format
What is a JT (.jt) file?
JT is Siemens’ lightweight format for visualizing and sharing 3D product data, published as ISO 14306. A JT file can hold tessellated levels of detail, exact B-Rep, product structure and PMI.
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Target format
What is an ASAT (.asat) file?
ASAT and ASAB are the assembly versions of the ACIS save file, in text and binary form. They store the product structure of models built on Spatial’s 3D ACIS Modeler kernel.
Frequently asked questions
The exact B-Rep that 3D InterOp reads from JT is written to ASAT; parts stored only as facets stay faceted.
Yes. 3D InterOp reads the JT product structure and writes it to ASAT.
An ACIS assembly (ASAT/ASAB) doesn’t support layers or colors at instance level, suppressed or hidden instances, or units at instance level.
Yes. 3D InterOp imports several levels of detail and the visual materials of JT files.
3D InterOp reads JT 8.x to 10.3 and 10.5 to 10.11.
3D InterOp writes ACIS R18 to 2026 1.0.
No. 3D InterOp reads JT but doesn’t write it. To send data back, write a neutral format such as STEP.
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Building software that needs to convert JT to ASAT?
3D InterOp is an SDK that lets your application read JT and write ACIS assembly alongside 30+ CAD and BIM formats.