Convert STP to Parasolid in your application
3D InterOp is a CAD interoperability SDK that lets your software read STEP files and write Parasolid (X_T, X_B), with exact B-Rep geometry carried across — no tessellation, no CAD license.
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 STEP · Writes Parasolid
- Exact geometry → exact geometry
- C++ / C# APIs
STP to Parasolid at a glance
Both formats store exact geometry, so the model stays exact. The differences are in the product data each one can carry.
| STEP (source) | Parasolid (target) | |
|---|---|---|
| Full name | Standard for the Exchange of Product model data | Parasolid transmit file (text X_T, binary X_B) |
| Standard / owner | ISO 10303 — AP203, AP214, AP242 | Proprietary — Siemens |
| File extensions | .stp, .step | .x_t, .x_b, .xmt_txt, .xmt_bin |
| Geometry | Exact B-Rep | Exact B-Rep |
| Assemblies / structure | Yes | Yes (Parasolid assembly structure) |
| PMI | Graphical and semantic (AP242) | PMI groups and attributes (3D InterOp representation) |
| 3D InterOp support | Read and write | Read and write · up to Parasolid 38 |
What's preserved, what changes
Here is what your application can expect to carry across from STEP to Parasolid.
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Preserved
Exact geometrySTEP solids and surfaces are written to Parasolid as exact B-Rep, with no tessellation.
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Preserved
Assembly structureThe Parasolid writer writes the STEP assembly structure, with options that control how part and sub-assembly instances are represented.
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Improved
Model qualityHealing options repair geometric and topological defects in the STEP data as it is written to Parasolid.
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Changes
PMI representationSTEP PMI (text, datums, GD&T, dimensions, roughness and flag notes) is written to Parasolid as groups and attributes, the representation 3D InterOp defines for PMI in Parasolid.
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Not carried
Point and vertex colorsThe Parasolid format has no point or vertex color, so these colors are not written.
Why software vendors add STP to Parasolid conversion
Hand models to kernel-based applications
Many CAD, CAM and CAE applications are built on the Parasolid kernel. Writing Parasolid gives them exact geometry they can load without another translation step.
Downstream modeling and analysis
An exact Parasolid 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 Parasolid kernel often prefer to exchange Parasolid files directly.
Things to check before you ship
- Choose the Parasolid version to write: the writer saves Parasolid 12 to 38.0.150.
- Writing Parasolid needs a Parasolid installation: there is no Parasolid Direct writer.
- Some non-Spatial Parasolid-based applications have trouble opening files that contain the empty body 3D InterOp uses to hold groups such as materials and attributes: test with the applications your users rely on.
- Reading semantic PMI from STEP AP242 requires a license in addition to the STEP Reader.
- 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 STEP (.stp) file?
STEP is the ISO 10303 standard for exchanging 3D product data between CAD systems. Its application protocols range from exact geometry (AP203, AP214) to full model-based definition with PMI (AP242).
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Target format
What is a Parasolid (X_T) file?
Parasolid is the geometric modeling kernel developed by Siemens and used by many CAD, CAM and CAE applications. Its transmit files store exact B-Rep models as text (.x_t) or binary (.x_b).
Frequently asked questions
Yes. The Parasolid writer writes the assembly structure. Its PreserveAssemblyStructure option controls whether extra assembly nodes are written to identify part and sub-assembly instances.
The Parasolid writer saves Parasolid 12 to 38.0.150, as .x_t, .xmt_txt, .x_b or .xmt_bin. Your application picks the version with the SaveVersion option.
Yes. Writing Parasolid needs a Parasolid installation: there is no Parasolid Direct writer.
Yes. STEP PMI (text, datums, GD&T, dimensions, roughness and flag notes) is written to Parasolid as groups and attributes, the representation 3D InterOp defines for PMI in Parasolid.
AP203, AP214 and AP242, from .stp, .step and .stpx files. Compressed .stpZ and .stpxZ files and .stpa files are read too.
Yes. 3D InterOp reads and writes both formats.
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Building software that needs to convert STP to Parasolid?
3D InterOp is an SDK that lets your application read STEP and write Parasolid alongside 30+ CAD and BIM formats.