I have introduced the posibility to start directly on the carrier.
With that patch you will have a --carrrier=id argument where id can either be
the pennant number configured in the nimitz scenario or the carriers name
also configured in the carriers scenario.
Additionaly you can use --parkpos=id to select different positions on the
carrier. They are also configured in the scenario file.
That includes the switch of the whole FGInterface class to make use of the
groundcache.
That means that an aircraft no longer uses the current elevation value from
the scenery class. It rather has its own local cache of the aircrafts
environment which is setup in the common_init method of FGInterface and
updated either manually by calling
FGInterface::get_groundlevel_m(lat, lon, alt_m);
or implicitly by calling the above method in the
FGInterface::_updateGeo*Position(lat, lon, alt);
methods.
A call get_groundlevel_m rebuilds the groundcache if the request is outside
the range of the cache.
Note that for the real usage of the groundcache including the correct
information about the movement of objects and the velocity information, you
still need to set up the groundcache in the usual way like YASim and JSBSim
currently does.
If you use the native interface, you will get only static objects correctly.
But for FDM's only using one single ground level for a whole step this is IMO
sufficient.
The AIManager gets a way to return the location of a object which is placed
wrt an AI Object. At the moment it only honours AICarriers for that.
That method is a static one, which loads the scenario file for that reason and
throws it away afterwards. This looked like the aprioriate way, because the
AIManager is initialized much later in flightgears bootstrap, and I did not
find an easy way to reorder that for my needs. Since this additional load is
very small and does only happen if such a relative location is required, I
think that this is ok.
Note that moving on the carrier will only work correctly for JSBSim and YASim,
but you should now be able to start and move on every not itself moving
object with any FDM.
this is basically the past patch I sent to the list and which should now
really (...!?!?) fix the no ground below aircraft problem.
Reasons:
I understood my remaining thinko I introduced with the prevous patch, and the
same thinko I made in my test cases.
The feedback from the list told me that it should help.
2.
I made YASim query the the ground cache at the wrong place. This one fixed
this, one can now land the bo105 on top of the oracle buildings :)
3.
Is a followup of the scenery center update code: Register the scenery center
transform at the time it is put into the scene graph not at creation time.
4.
I held that part back from the past hitlist patch, because I hoped that it
will be sufficient (and the last one was in fact the biggest part) without.
As some test cases from Melchior showed me, it is not. We have additionally
to the wrong computed transform from the prevous patch some roundoff
problems. This patch adds some small tolerance to for the point in triangle
test.
... may be one even needs to increase the eps value further if starting at
some tile boundaries still fails.
5.
That is a big chunk.
Tested now for two days while hunting the second patch :) .
That is a partial rewrite of the groundcache to use its own datastructures for
that flat scenegraph in the cache. The basic advantage is, what Erik
suggested, to precompute some often used values of these triangles. Also
allmost all computations are now in double precision which should decrease
(hopefully fix), together with a similar tolerance for some point in triangle
tests, the problems with 'no ground below aircraft'.
I am playing with octrees for the groundcache, that will finally solve the
performance problem when high triangular count models end up in the
groundcache. This patch is also some prework for those octrees ...
I have done a patch to eliminate the jitter of 3D-objects near the viewpoint
(for example 3D cockpit objects).
The problem is the roundoff accuracy of the float values used in the
scenegraph together with the transforms of the eyepoint relative to the
scenery center.
The solution will be to move the scenery center near the view point.
This way floats relative accuracy is enough to show a stable picture.
To get that right I have introduced a transform node for the scenegraph which
is responsible for that shift and uses double values as long as possible.
The scenery subsystem now has a list of all those transforms required to place
objects in the world and will tell all those transforms that the scenery
center has changed when the set_scenery_center() of the scenery subsystem is
called.
The problem was not solvable by SGModelPlacement and SGLocation, since not all
objects, especially the scenery, are placed using these classes.
The first approach was to have the scenery center exactly at the eyepoint.
This works well for the cockpit.
But then the ground jitters a bit below the aircraft. With our default views
you can't see that, but that F-18 has a camera view below the left engine
intake with the nose gear and the ground in its field of view, here I could
see that.
Having the scenery center constant will still have this roundoff problems, but
like it is now too, the roundoff error here is exactly the same in each
frame, so you will not notice any jitter.
The real solution is now to keep the scenery center constant as long as it is
in a ball of 30m radius around the view point. If the scenery center is
outside this ball, just put it at the view point.
As a sideeffect of now beeing able to switch the scenery center in the whole
scenegraph with one function call, I was able to remove a one half of a
problem when switching views, where the scenery center was far off for one or
two frames past switching from one view to the next. Also included is a fix
to the other half of this problem, where the view position was not yet copied
into a view when it is switched (at least under glut). This was responsible
for the 'Error: ...' messages of the cloud subsystem when views were
switched.
I have some small updates to the ground cache.
- Remove the usage of dynamic_cast where it is known that the result will be
non null.
- Renormalize the surface normal in double precision.
- Place the groundcaches center at the point it was requested not at the
scenery center. This fixes the problems with JSBSim's trimming together with
the ground cache. Now I am ready to commit JSBSim's ground cache usage.
I still work on getting the YASim models see the detailed environment
especially the carrier.
I have *forgotten* to initialize and to destruct the ground cache object!
Oooopppss!
I have now split out the ground cache functions into src/FDM/groundcache.[ch]xx
Attached are the two files and the patch to integrate that cache into
FGInterface.
The code is nowhere used at the moment, the fdm's need to be updated to use
that ground cache. The JSBSim-dropin.tar.gz from Martins ftp server does this
for example.
The carrier's scenegraph is not yet processed to be visible for ground
intersection testing. So the only benefit up to now is that the api is set
up. Using this I can put the changes to make JSBSim work with that into
JSBSim's cvs. Also I aim to provide Andy a patch to make use of that with
YASim.
