[QGIS-Developer] Scale z value to match 3d view dem scaling?

[Nyall Dawson]

Hi all (especially Martin),

I was chatting with Mathieu trying to work out if there was a bug in
3d map views, but it turns out that it was just a misunderstanding on
my part. I thought that if I had e.g. a pointz dataset (with z value
set to dem spot height) and a dem, the points should always be placed
exactly on the dem when altitude clamping = absolute.

It turns out that this is only the case if the dem vertical scale is
set to 1.0. If I increase the scale, then the point z values aren't
scaled to match and end up sitting below the dem.

To me this is a bug, because vertical scale is a view dependent "data
visualisation" setting only, and shouldn't require modification of the
original data itself (i.e. manually scaling the point z values to
match the vertical scale*).

Is this intended behavior? (and if so, can it be rethought?)

Nyall



* this is non-trivial - there's NO easy way in qgis to scale z values
(you'd need custom python code to do this)