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<p class="MsoNormal"><span style="font-size:11.0pt;mso-fareast-language:EN-US">Hi Chris!<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;mso-fareast-language:EN-US">It is a bit hard to understand what you have done just from the images. What have you done different in the two attempts? Why are they different? And why can’t you use
the brown one if it is working correctly? Does the pink layer allow z-geometries?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Franklin Gothic Book",sans-serif;color:black">Med vänliga hälsningar<o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Franklin Gothic Book",sans-serif;color:black"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Franklin Gothic Book",sans-serif;color:black">Karl-Magnus Jönsson</span></b><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">Från:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> QGIS-User <qgis-user-bounces@lists.osgeo.org>
<b>För </b>Chris Rogers via QGIS-User<br>
<b>Skickat:</b> den 15 februari 2026 14:04<br>
<b>Till:</b> qgis-user@lists.osgeo.org<br>
<b>Ämne:</b> [Qgis-user] Polygons with heights<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I'm trying to make a road bridge over a railway by making a gentle embanked slope up to the bridge, then a slope down. So I make the polygon (with z values) to represent the plan shape (see first attachment). The attachment shows two attempts,
one brown, one pink. When I now do a 3d view with Qgis2threejs, we see the second attachment. The brown bridge is correctly represented, but the pink bridge has the wrong shape.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Why are they different, how do we get the brown shape rather than the pink one?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I next want to raise the bridge to the raster layer. I managed to do this with the brown shape by firstly raising the polygon to the raster (I forget exactly how this was done, but I think I used the drape function, then raised some of
the vertices by the required amount). Draping the pink one does not raise the z-values. I also tried the
<i>Sample raster values</i> function, but this crashed the QGIS session.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">What I'm trying to do looks to be quite a simple and natural thing - maybe there is a clean way to do it in QGIS, but I've not been able to find it ...<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thanks!<o:p></o:p></p>
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