Hello, I would like to modify the z coordinate of a PointZ layer using a field.
In qgis 2.18 I could do that with a field function, and using .setZ on
the feature as a side effect of a field calculator invocation.
The field function looked like this:
@qgsfunction(args='auto', group='Custom')
def setZtoValue(newZ, feature, parent):
""" This function sets the Z coordinate to the provided value and
returns the new point. """
point = feature.geometry().geometry()
point.setZ(newZ)
return feature.geometry()
However, in qgis 3.4 I cannot figure out the equivalent field function
since the API changed. Here is what I have:
def setZtoValue(newZ, feature, parent):
""" This function sets the Z coordinate to the provided value and
returns the new point. """
verts = feature.geometry().constGet().vertices()
for v in verts:
v.setZ(newZ)
return feature.geometry()
[never mind the formatting]
This does something but then at the end I get this error:
An error occurred while evaluating the calculation string: 'NoneType'
object has no attribute 'vertices'
and the z component is not updated.
There are other ways to load in 3d points as 3d geometry but the flow
of loading the map points with an elevation/depth field, and then just
populating the z coordinate with the field value may suggest itself
first.
I know one can construct wkt to import, or perhaps generate new
geometry in a script and replace the existing geometry, but just
updating the the existing z would seem most straightforward. Is it
possible ?
Any feedback much appreciated, -Andreas
--
Andreas Plesch
Waltham, MA 02453
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