Approximate B-Spline Profile Point Lists by defining a Control Point Number #1277
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…hout setter. Also, later no casting needed
Additionally added options: User can define the approximation error method, currently: root mean square error or maximum error. Furthermore, the user can pass an index list within the CPACS configuration to define which points should still be interpolated. The other points, however, are approximated. The unittests needed to be changed to test for this behaviour. Also, a mistake was fixed, since the was a confusion regarding 0-based and 1-based indexing within th logic of interpolation indices.
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- Misses 7544 7672 +128
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Link to the corresponding CPACS prototype in WingMates project: https://gitlab.dlr.de/wingmates-project/cpacs/-/blob/newLofting/schema/cpacs_schema.xsd?ref_type=heads |
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General
This PR introduces the possibility to create b-spline profiles by approximating the user-set CPACS point list.
This is implemented for fuselage profiles and wing airfoils currently. It is still possible to define an index list of points that should be interpolated.
Thanks to @sdeinert for coming up with the CPACS definition!!
We extended it by the option to pass the error computation method and the optional index list for points that should be interpolated.
@MarAlder what do you think about our suggestion to extend the CPACS schema?
Code Behaviour
The user can now define the wanted number of control points that is used to approximate the profile. When kinks or guide curves are defined, this number may still be larger than what is defined in CPACS, for mathematical reasons. Nevertheless, the user now has more flexibility to determine the geometric behaviour of each profile. As a natural result from this reduced number of control points, an approximation error is introduced. The user can currently select from the computation as the root mean square error or the maximum error within CPACS. The respective choice and value are printed within the
TiGLCreatorGUI for better feedback.In CPACS we also defined the other way round: Meaning, that a maximum tolerance for the approximation error can be defined and TiGL defines the control point number on its own. But, this still needs to be implemented in another pull request.
Unittests are added for both a wing and fuselage profile.
Implementation Details and Code Refactorings
The present implementation comes with quite a few changes and refactorings of yet existing code.
WireCachetype defined insrc/wing/CTiglWingProfilePointList.his split up. Before, it contained both the opened and closed wire. The save computation time and output, the cache is split into two different ones. Only the needed one (closed or opened) is computed. For that, parts of the class had the be rewritten.src/geometry/CTiglApproximateBsplineWirewas refactored to account for the new CPACS nodes and for it to store the necessary variables.src/geometry/CTiglBSplineApproxInterpand its already defined functions which is almost unused up to now. Here, the error computation is changed to be more accurate. This is also the explanation for the needed change of the unittest value. Now, the approximation error is computed based on the difference between the beforehand defined points in the point list and an (approximation) of their projection on the new b-spline curve. Also, the error actual computation (2 point vectors) is outsourced to functions insrc/common/tiglcommonfunctions. The function is passed as a function pointer to thesolvemethod for more flexibility as we allow different ways of computation.src/geometry/CTiglApproximateBsplineWireis now also based on CTiglBSplineApproxInterp to make use of existing code and to be consistent with the fuselage implementation. Before, an OCCT-function was called here. However, we wanted to define the number of control points which was not really possible with the OCCT-function.computeParamsfunctions fromsrc/geometry/CTiglInterpolatePointsWithKinkshas to move from an anonymous namespace into thetiglnamespace since it is also needed outside from this class.Fixes #1276.
Checklist: