On 6/7/23 11:42, Mathieu wrote:
A bilinear extrapolation seems to be a suitable first try since the shape
functions are bilinear.
Going this way, I would compute the gradient of the function at a point at the
boundary to come up with the extrapolated function value.
Call the point outside the grid P, I would project P to the closest at the
boundary of the triangulation and evaluate the gradient there.
So, given P, how can I find the closest point at the boundary?
Or would you choose a different point at the boundary?
This is feasible, though finding the closest vertex is an expensive operation.
For this to work, you will have to find which cell is closest to the point in
question, for which I would use
GridTools::find_closest_vertex()
and
GridTools::find_cells_adjacent_to_vertex()
Best
W.
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Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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