[Qgis-user] 3D View Scaling

[Adam Dershowitz]

I’m having an issue with a 3D view, that has come up before.  I’ve simplified it and made a few images to explain the problem.

I sometimes work with 3D points, such as points that represent the flight of an aircraft.  If there are points that are over a DEM, then scaling is not handled as expected.  For an example, I created a few points in a layer and a polygon in another layer, both above a DEM layer.  I set the elevation for each of the points and the polygon corners to be above the DEM elevation.  I then set Elevation Clamping for both the points and polygon to be absolute.  If I open a  3D view and set the elevation to come from the dEM I get just what I would expect.  the points and the polygon show as just above the DEM.  



However, if I then set the vertical scale to be 2.0, for example, the polygon stays above the DEM, as I would expect.  But, the points end up below the DEM, so are no longer visible:



This seems like a bug to me.  So, changing the vertical scaling, changes the vertical scale of the DEM, and the corresponding height of a polygon, but it does not change the height of points.  

The only work around that I’ve found is to manually create a new point layer and make the elevation for each point twice what it actually is.  Then, if I view that layer in 3D, with the scale at 2.0, the points show up as I would expect.  I’m using version QGIS 3.8, but I’ve seen this problem in a  number of older versions as well.  I’ve also tried changing the settings for the layer from absolute to other altitude clipping,  but that doesn’t seem to help.  The stored altitude values for the polygon, DEM, and points are all meters above sea level.

Any suggestions or fixes?

Thanks,


--Adam
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