Convert NWD to ASAT in your application
3D InterOp is a CAD interoperability SDK that lets your software read NWD files and write ASAT, carrying across the exact geometry the NWD 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 Navisworks · Writes ACIS assembly
- Mixed geometry → exact geometry
- C++ / C# APIs
NWD to ASAT at a glance
Navisworks 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.
| Navisworks (source) | ACIS assembly (target) | |
|---|---|---|
| Full name | Navisworks document and cache files | ACIS assembly, text (ASAT) and binary (ASAB) |
| Standard / owner | Autodesk | Spatial (3D ACIS Modeler) |
| File extensions | .nwd, .nwc | .asat, .asab |
| Geometry | Mostly tessellated, B-Rep for cylinder and elliptical shapes | Exact B-Rep |
| Assemblies / structure | Yes | Yes |
| 3D InterOp support | Read only | Read and write |
What's preserved, what changes
Here is what your application can expect to carry across from Navisworks to ACIS assembly.
-
Preserved
Exact geometryExact B-Rep read from NWD is written to ASAT as exact geometry.
-
Preserved
Product structureThe NWD product structure is written to ASAT.
-
Changes
Mostly faceted modelNavisworks models are mainly read as visualization data; exact B-Rep is extracted only for cylinder and elliptical shapes.
Why software vendors add NWD 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 NWD input: Navisworks 2011 to 2026 (.nwd and .nwc).
- 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 a Navisworks (.nwd) file?
NWD is Autodesk Navisworks’ document format, a compact snapshot of a coordination model that combines files from many design tools. NWC files are the cache files Navisworks creates when it opens a native file.
-
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 NWD is written to ASAT; parts stored only as facets stay faceted.
Yes. 3D InterOp reads the NWD 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.
Mostly not. Navisworks models are read as visualization data; exact B-Rep is extracted only for cylinder and elliptical shapes.
3D InterOp reads Navisworks 2011 to 2026 (.nwd and .nwc).
3D InterOp writes ACIS R18 to 2026 1.0.
No. 3D InterOp reads NWD but doesn’t write it. To send data back to Navisworks users, write a format Navisworks opens, such as IFC.
-
Building software that needs to convert NWD to ASAT?
3D InterOp is an SDK that lets your application read Navisworks and write ACIS assembly alongside 30+ CAD and BIM formats.