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<p>from the docs ...</p>
<p>****It can only be used to render point data****</p>
<h4 style="box-sizing: border-box; margin-top: 0px; font-weight:
700; font-family: "Roboto Slab", ff-tisa-web-pro,
Georgia, Arial, sans-serif; font-size: 18.4px; color: rgb(64, 64,
64); font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; letter-spacing: normal; orphans: 2;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: 2; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(252, 252,
252); text-decoration-style: initial; text-decoration-color:
initial;"><a class="toc-backref"
href="https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#id15"
style="box-sizing: border-box; color: rgb(64, 64, 64);
text-decoration: none; cursor: pointer; outline-width: 0px
!important; user-select: auto !important;"><span
class="section-number" style="box-sizing: border-box;">12.2.2.2.6.<span> </span></span>The
Vector Field Marker</a></h4>
<p class="" style="box-sizing: border-box; line-height: 24px;
font-size: 16px; margin: 0px 0px 24px; color: rgb(64, 64, 64);
font-family: Lato, proxima-nova, "Helvetica Neue",
Arial, sans-serif; font-style: normal; font-variant-ligatures:
normal; font-variant-caps: normal; font-weight: 400;
letter-spacing: normal; orphans: 2; text-align: start;
text-indent: 0px; text-transform: none; white-space: normal;
widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;">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.</p>
<p style="box-sizing: border-box; line-height: 24px; font-size:
16px; margin: 0px 0px 24px; color: rgb(64, 64, 64); font-family:
Lato, proxima-nova, "Helvetica Neue", Arial, sans-serif;
font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-weight: 400; letter-spacing:
normal; orphans: 2; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;">The vector field is
defined by attributes in the data, which can represent the field
either by:</p>
<ul class="simple" style="box-sizing: border-box; margin: 0px 0px
24px; padding: 0px; list-style: disc; line-height: 24px; color:
rgb(64, 64, 64); font-family: Lato, proxima-nova, "Helvetica
Neue", Arial, sans-serif; font-size: 16px; font-style:
normal; font-variant-ligatures: normal; font-variant-caps: normal;
font-weight: 400; letter-spacing: normal; orphans: 2; text-align:
start; text-indent: 0px; text-transform: none; white-space:
normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width:
0px; background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;">
<li style="box-sizing: border-box; list-style: disc; margin-left:
24px;">
<p style="box-sizing: border-box; line-height: 24px; font-size:
16px; margin: 0px;"><strong style="box-sizing: border-box;
font-weight: 700;">cartesian</strong><span> </span>components
(<code class="docutils literal notranslate" style="box-sizing:
border-box; font-family: SFMono-Regular, Menlo, Monaco,
Consolas, "Liberation Mono", "Courier
New", Courier, monospace; font-size: 12px; white-space:
nowrap; max-width: 100%; background: rgb(255, 255, 255);
border: 1px solid rgb(225, 228, 229); padding: 2px 5px;
color: rgb(231, 76, 60); overflow-x: auto;"><span
class="pre" style="box-sizing: border-box;">x</span></code><span> </span>and<span> </span><code
class="docutils literal notranslate" style="box-sizing:
border-box; font-family: SFMono-Regular, Menlo, Monaco,
Consolas, "Liberation Mono", "Courier
New", Courier, monospace; font-size: 12px; white-space:
nowrap; max-width: 100%; background: rgb(255, 255, 255);
border: 1px solid rgb(225, 228, 229); padding: 2px 5px;
color: rgb(231, 76, 60); overflow-x: auto;"><span
class="pre" style="box-sizing: border-box;">y</span></code><span> </span>components
of the field)</p>
</li>
<li style="box-sizing: border-box; list-style: disc; margin-left:
24px;">
<p style="box-sizing: border-box; line-height: 24px; font-size:
16px; margin: 0px;">or<span> </span><strong style="box-sizing:
border-box; font-weight: 700;">polar</strong><span> </span>coordinates:
in this case, attributes define<span> </span><code
class="docutils literal notranslate" style="box-sizing:
border-box; font-family: SFMono-Regular, Menlo, Monaco,
Consolas, "Liberation Mono", "Courier
New", Courier, monospace; font-size: 12px; white-space:
nowrap; max-width: 100%; background: rgb(255, 255, 255);
border: 1px solid rgb(225, 228, 229); padding: 2px 5px;
color: rgb(231, 76, 60); overflow-x: auto;"><span
class="pre" style="box-sizing: border-box;">Length</span></code><span> </span>and<span> </span><code
class="docutils literal notranslate" style="box-sizing:
border-box; font-family: SFMono-Regular, Menlo, Monaco,
Consolas, "Liberation Mono", "Courier
New", Courier, monospace; font-size: 12px; white-space:
nowrap; max-width: 100%; background: rgb(255, 255, 255);
border: 1px solid rgb(225, 228, 229); padding: 2px 5px;
color: rgb(231, 76, 60); overflow-x: auto;"><span
class="pre" style="box-sizing: border-box;">Angle</span></code>.
The angle may be measured either clockwise from north, or
Counterclockwise from east, and may be either in degrees or
radians.</p>
</li>
<li style="box-sizing: border-box; list-style: disc; margin-left:
24px;">
<p style="box-sizing: border-box; line-height: 24px; font-size:
16px; margin: 0px;">or as<span> </span><strong
style="box-sizing: border-box; font-weight: 700;">height
only</strong><span> </span>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.</p>
</li>
</ul>
<p style="box-sizing: border-box; line-height: 24px; font-size:
16px; margin: 0px 0px 24px; color: rgb(64, 64, 64); font-family:
Lato, proxima-nova, "Helvetica Neue", Arial, sans-serif;
font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-weight: 400; letter-spacing:
normal; orphans: 2; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;">The magnitude of field</p>
<p style="box-sizing: border-box; line-height: 24px; font-size:
16px; margin: 0px 0px 24px; color: rgb(64, 64, 64); font-family:
Lato, proxima-nova, "Helvetica Neue", Arial, sans-serif;
font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-weight: 400; letter-spacing:
normal; orphans: 2; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;"><br>
</p>
<div class="moz-cite-prefix">Am 13.11.2020 um 11:34 schrieb Andreas
Neumann:<br>
</div>
<blockquote type="cite"
cite="mid:9d5955ce-6f3b-14ba-b27c-5f409d3382cd@carto.net">Or even
easier: use the "Vector Field Marker":
<br>
<br>
<a class="moz-txt-link-freetext" href="https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#the-vector-field-marker">https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#the-vector-field-marker</a>
<br>
<br>
Am 13.11.20 um 11:33 schrieb Andreas Neumann:
<br>
<blockquote type="cite">Hi,
<br>
<br>
Yes - you can use Geometry Generators for that. Use the
make_point() and make_line() expressions for that.
<br>
<br>
See
<a class="moz-txt-link-freetext" href="https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?highlight=geometry%20generator#the-geometry-generator">https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?highlight=geometry%20generator#the-geometry-generator</a><br>
<br>
Greetings,
<br>
Andreas
<br>
<br>
Am 13.11.20 um 11:26 schrieb L.W.:
<br>
<blockquote type="cite">Hi,
<br>
<br>
is it possible to draw automatically a line between two points
defined
<br>
by 4 fields (x1,y1 - x2,y2) in an attributetable?
<br>
<br>
but I do not want to add a line-layer based on this table nor
want to
<br>
draw the line by hand.
<br>
<br>
thanks
<br>
<br>
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