[Qgis-user] Dynamic Line

[Andreas Neumann]

Yes, you need point data to start from, but then vectors can bei/are 
generated from the attributes you mentioned.

Andreas

Am 13.11.20 um 11:47 schrieb L.W.:
>
> from the docs ...
>
> ****It can only be used to render point data****
>
>
>         12.2.2.2.6.The Vector Field Marker
>         <https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#id15>
>
> The vector field marker is used to display vector field data such as 
> earth deformation, tidal flows, and the like. It displays the vectors 
> as lines (preferably arrows) that are scaled and oriented according to 
> selected attributes of data points. ****It can only be used to render 
> point data****; line and polygon layers are not drawn by this symbology.
>
> The vector field is defined by attributes in the data, which can 
> represent the field either by:
>
>  *
>
>     *cartesian*components (|x|and|y|components of the field)
>
>  *
>
>     or*polar*coordinates: in this case, attributes
>     define|Length|and|Angle|. The angle may be measured either
>     clockwise from north, or Counterclockwise from east, and may be
>     either in degrees or radians.
>
>  *
>
>     or as*height only*data, which displays a vertical arrow scaled
>     using an attribute of the data. This is appropriate for displaying
>     the vertical component of deformation, for example.
>
> The magnitude of field
>
>
> Am 13.11.2020 um 11:34 schrieb Andreas Neumann:
>> Or even easier: use the "Vector Field Marker":
>>
>> https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#the-vector-field-marker 
>>
>>
>> Am 13.11.20 um 11:33 schrieb Andreas Neumann:
>>> Hi,
>>>
>>> Yes - you can use Geometry Generators for that. Use the make_point() 
>>> and make_line() expressions for that.
>>>
>>> See 
>>> https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?highlight=geometry%20generator#the-geometry-generator
>>>
>>> Greetings,
>>> Andreas
>>>
>>> Am 13.11.20 um 11:26 schrieb L.W.:
>>>> Hi,
>>>>
>>>> is it possible to draw automatically a line between two points defined
>>>> by 4 fields (x1,y1 - x2,y2) in an attributetable?
>>>>
>>>> but I do not want to add a line-layer based on this table nor want to
>>>> draw the line by hand.
>>>>
>>>> thanks
>>>>
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