Regarding importing to cpacs format

[namanshetty29]

I am trying to understand
Cessna 172 Skyhawk Mockcpacs.txt
CPACS. I have a .xml file from openvsp or other source and I want to read that with CPACS, what are the modifications needed to be made

[MarAlder]

If you have an aircraft geometry in OpenVSP (.vsp3) or another XML-based format and you wish to read it using CPACS, some modifications are necessary to ensure compatibility. CPACS (Common Parametric Aircraft Configuration Schema) is a standardized XML data model used for defining and exchanging aircraft configurations, particularly in the context of computational aerodynamics, structural analysis, and overall aircraft design.

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• Documentation
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Key Considerations for Conversion

1. CPACS Structure vs. OpenVSP XML

OpenVSP and CPACS both use XML, but their schema structures are different. OpenVSP files define aircraft geometries in a hierarchical manner, while CPACS follows a structured schema with predefined elements, primarily under the aircraft/model nodes.

Your provided file (Cessna 172 Skyhawk Mockcpacs.txt) has some elements that seem to come from OpenVSP but also contain CPACS-specific elements. The modifications required depend on:

• The version of CPACS you are targeting (e.g., 3.4, 3.5, or newer versions)
• The completeness of the OpenVSP export
• The structural elements needed for CPACS compatibility

2. Required Modifications

To ensure the OpenVSP XML can be read properly as a CPACS file, you will need to:

A. Modify the Header

• Ensure that the CPACS version is explicitly defined under <header>. Your file mentions cpacsVersion>3.5</cpacsVersion>, which is correct for CPACS 3.5, but double-check that all elements conform to this version.
• Verify that versionInfos contains correct metadata.

B. Convert the Geometry Definitions

• CPACS defines the aircraft structure under <vehicles> → <aircraft> → <model>, while OpenVSP may use a different hierarchy.
• The <Vehicle> and <ParmContainer> structures in your file need to be mapped to geometry elements in CPACS, typically <wings>, <fuselages>, <landingGears>, <engines>, etc..

C. Adjust Component Definitions

• OpenVSP stores fuselage, wings, and control surfaces under <Geom> elements.
• In CPACS, these must be structured under <wings>, <fuselages>, and <controlSurfaces>.
• OpenVSP’s ParmContainer includes many parameters that do not directly translate to CPACS. These may need manual conversion or scripting to transform into CPACS-compatible nodes.

D. Remove or Map OpenVSP-Specific Attributes

• Elements such as <AttributeCollection> and <AdvLinkSettings> in your file are OpenVSP-specific and do not exist in CPACS.
• Watermark settings, light parameters, and DXF/STEP/STL export settings do not belong in CPACS and should be removed unless necessary.

E. Convert and Define Materials and Mass Properties

• CPACS includes dedicated <materials> and <massBreakdown> sections.
• OpenVSP may define material properties within the geometry, but CPACS requires a structured approach with predefined material entries.

3. Automating the Conversion

There is not translator from OpenVSP to CPACS available yet. Since XML conversions can be tedious, it is recommended to use a script-based approach:

• Python + TiXI: TiXI is based on libxml2. It is typically used for working with CPACS files, but still very generic when it comes to working with XML.
• Python + lxml: Use Python libraries like xml.etree.ElementTree or lxml to parse and transform the OpenVSP XML to CPACS format.
• TiGL: Use the geometry library TiGL library to check your conversion to CPACS.

4. Validation

• Once modified, validate the CPACS file using the CPACS schema.
• Open the modified file in a CPACS-compatible tool like TiGL-Viewer.

Conclusion

To successfully read your OpenVSP-based XML in CPACS, you need to:

1. Adjust the XML structure to match CPACS standards.
2. Map OpenVSP elements to CPACS equivalents.
3. Remove unnecessary attributes that are OpenVSP-specific.
4. Validate the resulting file with CPACS schema and tools.