Convert DWG to ASAT in your application
3D InterOp is a CAD interoperability SDK that lets your software read DWG files and write ASAT, carrying across the exact geometry the DWG 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 DWG · Writes ACIS assembly
- Mixed geometry → exact geometry
- C++ / C# APIs
DWG to ASAT at a glance
DWG 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.
| DWG (source) | ACIS assembly (target) | |
|---|---|---|
| Full name | AutoCAD Drawing | ACIS assembly, text (ASAT) and binary (ASAB) |
| Standard / owner | Autodesk | Spatial (3D ACIS Modeler) |
| File extensions | .dwg | .asat, .asab |
| Geometry | 2D drawings and 3D data | Exact B-Rep |
| Assemblies / structure | Blocks and layers | Yes |
| 3D InterOp support | Read; write drawings only | Read and write |
What's preserved, what changes
Here is what your application can expect to carry across from DWG to ACIS assembly.
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Preserved
Exact geometryExact B-Rep read from DWG is written to ASAT as exact geometry.
Why software vendors add DWG 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 DWG input: DXF/DWG 2.5 to 2027.
- A DWG file that only contains 2D drawings has no 3D geometry to write.
- 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 DWG (.dwg) file?
DWG is the native file format of Autodesk AutoCAD, used for 2D drawings and 3D models. It is one of the most widespread formats for technical drawings.
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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 DWG is written to ASAT; parts stored only as facets stay faceted.
An ACIS assembly (ASAT/ASAB) doesn’t support layers or colors at instance level, suppressed or hidden instances, or units at instance level.
Then there is no 3D geometry to write to ASAT: 3D InterOp needs 3D content in the DWG file for this conversion.
Both the 2D content (drawing sheets) and the 3D data stored in the file.
No. 3D InterOp writes drawing sheets to DXF and DWG, but 3D export to these formats isn’t supported. To send 3D data back to AutoCAD users, write a neutral 3D format such as STEP.
3D InterOp reads DXF/DWG 2.5 to 2027.
3D InterOp writes ACIS R18 to 2026 1.0.
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Building software that needs to convert DWG to ASAT?
3D InterOp is an SDK that lets your application read DWG and write ACIS assembly alongside 30+ CAD and BIM formats.