You might want to look into
/OpenSceneGraph/include/osgSim/OverlayNode
Cheers
Norman
On Jun 14, 2009, at 10:19 AM, Curtis Olson wrote:
Hi Fred,
Glad to see someone is starting to nibble at the 8.50 format and
figure it out. If you are developing code that takes the bezier
outlines and can turn that into a polygon representation, then it
shouldn't be terribly difficult to add that into genapts.
For lines and markings, I think the easiest path in the short term
will be to cut those into the surface. However, this can explode
the polygon count and rendering load so we need to be careful, but
it should be manageable if we don't get too crazy with lots of small
segments around curves to make them look perfectly smooth.
I've never played around with glPolygonOffset in the context of btg
files (terragear/genapts) so I don't believe there's any support
there. It's difficult because airport surfaces are curved and are
not planar, so most likely any use of glPolygonOffset will not be
perfect and there will be places where the lines z-fight with the
underlying surface ... unless we really go crazy with a large offset
value in which case the lines could bleed through some of the
surfaces when they should be hidden behind them. Still it might be
worth playing around with to see what kind of results are actually
achievable.
I wonder what tricks and approaches the gaming community uses for
drawing clear and realistic roads? The problem with cutting the
lines into the surface as polygons is that (1) you explode the
polygon count and (2) you have hard aliased edges which can become
distracting in the distance. Cooking the lines into the surface
texture gets rid of the aliasing problem, but then you explode your
texture memory requirements and need to do a lot of work to generate
those textures on the fly, or generate them once and store them.
And drawing the lines on top using glPolygonOffset is hard to do
well when you are dealing with non-planer surfaces and the visual
result of glPolygonOffset (at least historically) has not been
consistent across different video cards and vendors. It's a
difficult challenge to do well.
Regards,
Curt.
On Sun, Jun 14, 2009 at 6:56 AM, Frederic Bouvier wrote:
Hi,
I committed the support to read new X-Plane 850 file format in
flightgear. That doesn't mean that airports will look different in
current scenery because TerraGear tools have not been updated yet, but
this is the first step to support the format.
Here are two screenshots comparing the ground radar with the different
data :
http://frbouvi.free.fr/flightsim/KSBD-810.png
http://frbouvi.free.fr/flightsim/KSBD-850.png
The Google Maps link: http://tinyurl.com/n9khev
You should notice the smooth curves in the 850 screenshot.
The parser should read current data normally, and nobody should see
the
difference until we change the data.
Please shout if you find something broken or overlooked. (actually
something is broken in the 777 ground radar, but it's not me ;-) )
Curt wrote (about linear features) :
> Fred, were you thinking of cutting these lines into the surface
(with
> hard polygon edges) or drawing them over the top like with a
> glPolygonOffset() approach? Or something else? It would be really
> great to be able to add taxi lines and other markings to our
airports.
I didn't really thought about it yet. I am open to ideas. Does
the .btg
file format support the glPolygonOffset approach ?
Regards,
-Fred
--
Frédéric Bouvier
http://my.fotolia.com/frfoto/ Photo gallery
http://fgsd.sourceforge.net/ FlightGear Scenery Designer
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