What pointdata are filled in to a cut mesh?

[baba-yaga]

Happy New Year, Marco and everyone!
If you cut off a mesh from a parent mesh that has pointdata, the new mesh also has pointdata, but what content does it have? I expect that the data of the vertices which exist in the parent mesh would be inherited, but what is filled in for the new points added along the cut line? Here is a demo:

K=Cube().clean()
K.pointdata['pids'] = np.arange(K.npoints)  # add vertex ids as pointdata
# cut off a corner:
pyramid = K.clone().cut_with_plane(origin=(0.3,0.3,0.3), normal=(1,1,1))
print(pyramid.pointdata['pids'])
# [6 7 5 4]
print(pyramid.vertices)
# [[ 0.5         0.5         0.5       ]
 # [ 0.5        -0.10000001  0.5       ]
 # [ 0.5         0.5        -0.10000001]
 # [-0.10000001  0.5         0.5       ]]
print(K.vertices[[6, 7, 5, 4]])
# [[ 0.5  0.5  0.5]
# [ 0.5 -0.5  0.5]
# [ 0.5  0.5 -0.5]
# [ 0.5 -0.5 -0.5]]

The K-vertex 6 is also in pyramid, as its pid was indeed inherited. But what are the added vertices pointdata? Although the first two looks like being taken from the closest K-vertex, the last one is totally obscure. Moreover, the pointdata in the cut-mesh may be duplicated:

pyramid2 = K.clone().cut_with_plane(origin=(-0.3,-0.3,-0.3), normal=(-1,-1,-1))
print(pyramid2.pointdata['pids'])
# [0 1 2 2]

So these are not related to the closest vertex which is unique.

[marcomusy]

Hi Sergei, Happy New Year to you as well!
What about this solution:
#1118 (comment)
Is it still a valid one?

what are the added vertices pointdata?

in principle the data for the new points is the result of an interpolation from the original values along the edge.

[baba-yaga]

Thank you, Marco! I remembered that I had already asked a similar question, but it does not show in my discussions because, apparently, I have used another account. I need to find a way to join them..