load terrain data (GfxCore::LoadDEM function)

[detrito]

Olly Betts <olly at survex.com> wrote:

> Currently the most detailed documentation for it lives on the wiki, as
> that allows us to improve it between releases:
> 
> https://trac.survex.com/wiki/TerrainData

hi Olly,

thanks for your reply full of detaily ;) I checked the wiki page, and
I found that "The terrain data currently needs to be in WGS84 lat/long."
is this still actual? my MNT has the same coordinate system then my
project (CH1903+_LV95 aka EPSG:2056) and I didn't get any error when I
loaded the terrain data.

> If it's not that, I'd guess it's some variant of BIL which my code
> doesn't cope with - however, I don't see the attachment you refer to
> so it's hard to say more.

here [1] the specs of my dtm. here [2] the survey project with the dtm
itself [2]

> The current terrain file reading is just something I knocked up
> quickly so I could get the rendering code working - I picked BIL/HGT
> as a really simple format in which usable terrain data for most of
> the world is available.  But but I've only tested with a few sources
> of such files, and the error checking is a bit minimal I'm afraid.

ok, maybe some error handling in case the surface don't cover the cave
could already help ;)

> Currently there's no explicit handling of the vertical datum, so the
> terrain will probably be offset from the underground data (for me by
> about 30m) so your millimitre precision may be rather wasted...

yes, I agree that mm-precision isn't necessary for a 3d visualisation,
but for high resolution DTMs, dm-prevision allow to get better shadows
on the topographic surface.

[1] http://luca.sgtraduzioni.ch/speleo/arcmap_dtm.png
[2] https://github.com/detrito/topo-folliu

ciao, Luca

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