Convert DWG to IGES in your application
3D InterOp is a CAD interoperability SDK that lets your software read DWG files and write IGES, 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 IGES
- Mixed geometry → exact geometry
- C++ / C# APIs
DWG to IGES at a glance
DWG can mix exact solids and facets; IGES stores exact geometry. Exact elements are written as exact geometry, and elements stored only as facets stay faceted.
| DWG (source) | IGES (target) | |
|---|---|---|
| Full name | AutoCAD Drawing | Initial Graphics Exchange Specification |
| Standard / owner | Autodesk | ANSI |
| File extensions | .dwg | .igs, .iges |
| Geometry | 2D drawings and 3D data | Exact B-Rep and surfaces |
| Assemblies / structure | Blocks and layers | No native assembly hierarchy |
| 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 IGES.
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Preserved
Exact geometryExact B-Rep read from DWG is written to IGES as exact geometry.
Why software vendors add DWG to IGES conversion
Legacy CAD and CAM systems
Many established engineering tools still consume IGES first. Writing it lets your users hand data to them without leaving your application.
Supplier and partner exchange
Some suppliers and manufacturing partners still specify IGES in their exchange requirements. Your software can meet them directly.
Geometry-only workflows
When a downstream process needs exact part geometry and nothing more, IGES is a simple, widely readable target.
Things to check before you ship
- Written IGES versions: IGES 5.3.
- 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 IGES (.igs) file?
IGES is one of the earliest neutral CAD formats, an ANSI standard for exchanging 2D and 3D geometry. It stores exact curves, surfaces and solids, but not the product structure and manufacturing data STEP can carry.
Frequently asked questions
The exact B-Rep that 3D InterOp reads from DWG is written to IGES; parts stored only as facets stay faceted.
Then there is no 3D geometry to write to IGES: 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 IGES 5.3.
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Building software that needs to convert DWG to IGES?
3D InterOp is an SDK that lets your application read DWG and write IGES alongside 30+ CAD and BIM formats.