Re: [Flightgear-devel] Properly rendering terrain data from FlightGear using OpenGL

[Sascha R. <rei...@no...>]

Am Freitag, den 04.09.2020, 18:54 +0200 schrieb Samuel CUELLA:
> On Thu, 03 Sep 2020 19:40:37 +0200
> Sascha Reißner <rei...@no...> wrote:
> > I dont know if it calculate also the local orientation, but thats
> > not
> > difficult to do. I remember some matrix calculation in the code, so
> > i
> > have played with rotated coordinate systems.
> > 
> I couldn't find it yet. I used a PDF document that explained the math
> to go from a cartesian ECEF to local NED (North East Down) vectors
> which gave me some results but not perfect.

The code need it to calculate the correct orientation of the approach
light system if you change or build a new one.
I think its the function 'projection' in vertex.c on line 231.
It takes the bounding sphere as local center and calculate the X/Y/Z
location of the vertex based on the local center and local orientation.
This will be stored in the vertex.projection.[x|y|z].
So vertex.projection.[x|y|z] is a localized coordinate where X and Y
build a horizontal plane (Y point to north) and Z is straight up.

-- 
best regards
Sascha

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