QGIS 3D - no terrain altitude binding for polygons / buildings

Question

My first post to this topic: QGIS 3D - no terrain altitude binding There I have had problems with 3D objects from a point layer. I solved this.

Now I have a problem with 3D objects from a polygon layer. I use polygons / buildings from osm. All buildings with the same high. Within qgis2threejs is all ok. But with QGIS 3D not: No altitude binding. But I need for my ideas 3D of QGIS, I can not use qgis2threejs. Any ideas to solve the problem? I need the same result as for the buildings within qgis2threejs.

I get only a good result if I use flat terrain.

Here a screenshots of the problem and of my settings:

above: The buildings with the black lines are examples, not the only wrong building-heigh-positions. The buildings left are OK, on the right wrong.

My settings:

Without terrain: no problems

Windows 10, QGIS 3.10.6

edit: try on QGIS 3.12.3: only crashes....oh....

Answer 1

The "Height" property in Layer Properties > 3D View is used to place the bottom of the 3d object. You should be able to specify an attribute which indicates the starting height for each feature. If you do not have this then you can calculate it from the terrain layer you are using.

Answer 2

Did you tried to change tile resolution to 1 or 2 px? If your computer does not allow to view this scene, try to decrease terrain file size while keeping original resolution of it.