Re: [Flightgear-devel] Fixing fgfs-construct crashes

[Martin S. <Mar...@mg...>]

Curtis Olson wrote:

> So this all sounds good (I think) except we now have to compute a point
> inside each material region.  Easy, right?  Well, except that all the
> published algorithms can tell you if a random point is inside a polygon or
> not, but they don't tell you how to manufacture a point that is guaranteed
> to be inside a polygon.

Well, there _is_ OpenSource software which is capable of reliably
creating points in polygons (GRASS GIS, just to present a prominent
example, they call them "centroids") and "terragear-cs" did have such a
thing in the past decade, but Ralf Gerlich finally decided to back it
out again because later processing steps in TerraGear were designed to
not having to deal with certain corner-cases for valid ! points in
polygons.  For more information, read thie fine comment in this diff:

  http://mapserver.flightgear.org/git/gitweb.pl?p=terragear-cs;a=commitdiff;h=8e0e2b6cef93ac689f611e93ca6250d33f243fbe;hp=e813c093fc444d9c36bb992768e37a1abb8c47d4

Therefore I'm still in favour of the long-term idea to drop the entire
poly-preprocessing from TerraGear and, instead, add a frontend to read
the entire land cover and roads from a GRASS database.  GRASS is
capable of doing all the clipping and "sliver" removal ("v.clean
tool=rmsa -c") in a topologically consistent and reliable way.

Cheers,
	Martin.
-- 
 Unix _IS_ user friendly - it's just selective about who its friends are !
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