[Qgis-user] Mesh interpolation technique

[Vincent Cloarec]

Hi,

Interpolation is done by linear interpolation. With quads, QGIS uses a
triangulation to interpolate values between vertices. There aren't other
interpolation methods for now. But indeed it could be good to add another
interpolation method for quads because the actual interpolation creates
bias.  Note that for rendering, it is possible to change the sample method
to "Neighbor average" that leads to render faces with the average value of
its vertices, but that does not change the value returned by Identify
Results.

For this other question, it is not possible to get the values of the
nearest vertex when extracting values from location in a points layer,
indeed, it could also be a nice feature. Maybe a workaround could be to
extract vertices as a vector layer, then using vector layer algs to do what
you want.

Regards,

Vincent

Le mer. 28 juin 2023 à 12:33, Domenico Micocci via QGIS-User <
qgis-user at lists.osgeo.org> a écrit :

> Dear all,
>
> I've just started working with mesh data in QGIS. In particular, I'm
> working with a regular 2D quad mesh; metadata are as follows:
> Mesh type faces
> Data type vertices
> Is vector No
>
> My QGIS version is 3.22.4
>
> I've noticed that interpolation is performed on faces and that
> interpolated values can be detected through the "Identify Results" Panel.
> However, it is not clear to me which interpolation technique is used and
> whether it is possible to change it or not. Moreover, does the properties
> selected through the Symbology Tab exert any influence on the interpolated
> values or does they only act on the mesh visualization?
>
> Similarly, I suppose that the tool "Export time series values from points
> of a mesh dataset" extracts a timeseries of interpolated values in the
> location(s) specified by a point layer. Is it possible to get the values of
> the nearest vertex of the mesh instead of the interpolated values?
>
> Thank you in advance for your kind support.
> Best regards,
>
> Domenico Micocci
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