[QGIS-Developer] Can't get values from QgsMeshLayer

[Enrico Ferreguti]

3.16
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Il mer 3 feb 2021, 16:26 Vincent Cloarec <vcloarec at gmail.com> ha scritto:

> Hi Enrico,
>
> As that will depend of the version of QGIS, which version do you use?
>
> Le mer. 3 févr. 2021 à 10:59, Enrico Ferreguti <enricofer at gmail.com> a
> écrit :
>
>> I'm trying to write a simple function for retrieving wind speed and
>> direction at a specified moment from a given grib file readable as mesh
>> layer the prototype script is the following:
>>
>> mesh = QgsMeshLayer("[path to the attached
>> grib]/20210202_211414_ICON_EU_P06_.grb2","test","mdal")
>> #mesh = iface.activeLayer()
>> p1 = QgsPointXY(1.60301, 38.38453)
>>
>> ds_group_index = 1
>>
>> for g in mesh.datasetGroupsIndexes():
>>     print ("MESH GROUP:", g,
>> mesh.datasetGroupMetadata(mesh.datasetIndexAtRelativeTime(h0,g)).name())
>>
>> for i in range(mesh.dataProvider().datasetCount(ds_group_index)):
>>     meta =
>> mesh.dataProvider().datasetMetadata(QgsMeshDatasetIndex(ds_group_index, i))
>>     t = meta.time()
>>     dataset = QgsMeshDatasetIndex(ds_group_index, i)
>>     value = mesh.datasetValue(dataset, p1)
>>     print ("VALUES P1",t,value.scalar(),value.x(),value.y())
>>
>> When I run the script I can get dataset names from metadata but I'getting
>> Nan as values
>> I verified that the grib is loadable in mapcanvas and the sample point is
>> within grib extent.
>> I read the note in api (
>> https://qgis.org/api/classQgsMeshLayer.html#a76a7ec072b4acaf45c1a10f5872c4948)
>> "It uses previously cached and indexed triangular mesh and so if the layer
>> has not been rendered previously (e.g. when used in a script) it returns
>> NaN value" so I tried to process an already loaded mesh (decomment line 2)
>> without luck.
>>
>> Is there anybody who can help me finding what I'm doing wrong? Thanks.
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>
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