[Qgis-user] MVP solid 3d

[Johannes Kröger (WhereGroup)]

Hi Gerald,

a PolygonZ is not a solid but a surface* that might be rotated in 3D space.

Your PolygonZ has the same Z coordinate for all its points so it is 
flat/orthogonal in reference to the vertical axis.

*: Depending on the Z coordinates a PolygonZ might not be a flat 
(potentially rotated) surface but a rather complex surface. E.g. if you 
have a polygon with 4 corners of which three have the same Z coordinate 
but one has a different one: There is no flat surface connecting all 
those points.  I don't know the correct term for this right now. 
Geometries like that are usually problematic. But 
https://gis.stackexchange.com/a/350117/51035 shows an example with such 
geometry being rendered "fine" in the QGIS 3D view.

Cheers, Hannes

On 3/13/25 19:39, Gerald Kogler via QGIS-User wrote:
> Hi!
>
> I'm trying without success to visualize a simple solid 3d object with 
> QGIS 3d Map View. The geometry is of type PolygonZ, but the 3d viewer 
> only shows it in 2 dimensions without Z values. All triangles are 
> shown on a plain.
>
> The layer definitly does have Z values, using for example 
> geom_to_wkt($geometry) does show me WKT values like:
>
> PolygonZ ((204594.00012206999235786 496779.0001220700214617 2998679.5, 
> 204771.00012206999235786 496783.0001220700214617 2998679.5, 
> 204881.00012206999235786 496802.0001220700214617 2998679.5, 
> 204594.00012206999235786 496779.0001220700214617 2998679.5))
>
> What do I miss, anything in the configuration which could be wrong? I 
> only manage to show the third dimension using extruding, that works 
> fine for example to show buildings from OpenStreetMaps.
>
> Anybody knows about a dummy Getting Started tutorial beside the 
> official QGIS docs about 3d Map View in order to make a really basic 
> example work?
>
> Thanks for your help
> Gerald
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-- 
Johannes Kröger / GIS-Entwickler/-Berater

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