Bug report #17789
3D windows not rendering negative z-values of geometry
|Affected QGIS version:||master||Regression?:||No|
|Operating System:||Easy fix?:||No|
|Pull Request or Patch supplied:||No||Resolution:||duplicate|
|Crashes QGIS or corrupts data:||No||Copied to github as #:||25685|
Adding a 3D-multipoint through the DB Manager hooked to PostGIS, does not render the points with negative z-values.
SELECT 1 AS id, ST_GeomFromText('MULTIPOINT(505105 6305783 -200, 505105 6305783 0, 505105 6305783 200)', 25832) AS geom
The same goes for single point geometries:
1 AS id,
ST_GeomFromText('POINT(505105 6305783 -200)', 25832) AS geom
2 AS id,
ST_GeomFromText('POINT(505105 6305783 0)', 25832) AS geom
3 AS id,
ST_GeomFromText('POINT(505105 6305783 200)', 25832) AS geom
Also the geometry in z = 0 is cut in half.
Version: OSGEO QGIS Master (2.99.0-255) of 4th Jan 2018
#1 Updated by Martin Dobias over 2 years ago
This is expected: by default the 3D view also renders "flat" terrain at zero elevation with map image as the terrain's texture - that's why the point at zero elevation is cut in half and the point with negative elevation does not appear (hidden under the terrain).
#2 Updated by Jakob Lanstorp over 2 years ago
Is the terrain's texture not just another 3D geometry that you should be able to pan through? Negative z-values is important for data like geological layers and sewer network systems. Normally you would set the surface to 0 meters. Negative values below surface positive above the surface. If I just have the 3D-geometry and no other layers in the map, there is still an imaginary 0 meter surface hiding the negative values.
#3 Updated by Martin Dobias over 2 years ago
Is the terrain's texture not just another 3D geometry that you should be able to pan through?
That's correct. There are few things special about it though compared to other 3D geometries, e.g. when dragging map with mouse we find out which point on the terrain user grabbed in order to move camera correctly.
The camera controller as of now also has a lock on maximum tilt angle so that user does not get under the terrain - something that is not desirable when not working with subsurface data. In a future release we should have options to allow users move the camera more freely to give more power to those working with subsurface data.
Shall we close this ticket?