[Qgis-user] MVP solid 3d

[Gerald Kogler]

Hi,

Thanks for your answers and the hint with flat Z coordinate. Now I 
managed to have MultiPolygonZ geometries with the complete 3d object 
saved as feature.

Here a sample layer as gpkg file [1] containing 64 objects from an 
arqueological excavation.

Objects do show up as plains in 3d Map View (QGIS 3.34), when I apply a 
Single Symbol in 3D View Properties, they do disappear so.

Thanks for your help
Gerald

[1] https://cloud.servus.at/s/Gigik6fAYZKGjib



On 14/3/25 9:17, Johannes Kröger (WhereGroup) via QGIS-User wrote:
> 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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