#1269 Local coordinates for BoundarySegment parametrization not uniform in AluGrid
Metadata
| Property | Value |
|---|---|
| Reported by | Carsten Gräser (graeser@math.fu-berlin.de) |
| Reported at | Mar 25, 2013 20:27 |
| Type | Bug Report |
| Version | Git (pre2.4) [autotools] |
| Operating System | Unspecified / All |
Description
If you insert a BoundarySegment with a parametrization into an AluGrid (simplex,2d) and refine it several times the local coordinates used in the parametrization are not uniformly distributed on the unit interval.
If you refine the grid n times, one would expect, that the parametrization is evaluated at i/n for values of i in {0,1,2,...,n}. In fact the local coordinates differ from this with increasing error for more refinement levels. This leads to distorted triangles at the boundary even for a perfect parametrization.
The attached example demonstrates this for a quarter arc of the unit circle. For 1,..,3 refinement levels (passed as command line argument) the grid looks OK. For 4 refinements one can see that the boundary faces do not have the same length. For 6 refinements there are even overlapping boundary elements.
This behaviour seems not to happen, if the BoundarySegment just interpolates between its vertices, so it is dependent on the actual parametrization function.