Overview

The TiGL Geometry Library can be used for easy processing of geometric data stored inside CPACS data sets. TiGL offers query functions for the geometry structure. These functions can be used for example to detect how many segments are attached to a certain segment, which indices these segments have, or how many wings and fuselages the current airplane configuration contains. This functionality is necessary because not only the modeling of simple wings or fuselages but also the description of quite complicated structures with branches or flaps is targeted. The developed library uses the Open Source software OpenCASCADE to represent the airplane geometry by B-spline surfaces in order to compute surface points and also to export the geometry in the IGES/STEP/STL/VTK format. The library provides external interfaces for C/C++, Python, MATLAB and FORTRAN.

For more information and examples, go to the TiGL website https://dlr-sc.github.io/tigl/.

In order to perform the modeling of wings and fuselages as well as the computation of surface points effectively, a geometry library was developed in C++. The library provides external interfaces for C and FORTRAN. Some of the requirements of the library were:

- Ability to read and process the information stored in a CPACS file for wings and fuselages,
- Possibility to extend to engine pods, landing gear and other geometrical characteristics,
- Ability to build up the three-dimensional airplane geometry for further processing,
- Ability to compute surface points in Cartesian coordinates by using common aircraft parameters,
- Possibility to be expanded by additional functions such as area or volume computations,
- Possibility to export the airplane geometry in the IGES format.

The developed library uses the Open Source software OpenCASCADE to represent the airplane geometry by B-spline surfaces in order to compute surface points and also to export the geometry in the IGES format. OpenCASCADE is a development platform written in C++ for CAD, CAM, and CAE applications which has been continuously developed for more than ten years. The functionality covers geometrical primitives (for example points, vectors, matrix operations), the computation of B-spline surfaces and boolean operations on volume models.

Apart from the already specified requirements above, the geometry library offers query functions for the geometry structure. These functions can be used for example to detect how many segments are attached to a certain segment, which indices these segments have, or how many wings and fuselages the current airplane configuration contains. This functionality is necessary because not only the modeling of simple wings or fuselages but also the description of quite complicated structures with branches or flaps is targeted.

In order to review the geometry information of the central data set a visualization tool, TiGL Viewer, was developed. The TiGL Viewer allows the visualization of the used airfoils and fuselage profiles as well as of the surfaces and the entire airplane model. Furthermore, the TiGL Viewer can be used to validate and test the implemented functions of the geometry library, for example the calculation of points on the surface or other functions to check data that belong to the geometry structure.