Re: [Flightgear-devel] Ground elevation problems.
Curtis L. Olson [EMAIL PROTECTED] said:
Ground elevation problems ...
I'm starting at KHAF (because it illustrates the problem pretty well.)
I'm using the A4, but the problem is with any aircraft.
Below is the fix for that bug. It's just a one line change. My apologies if
this mailer screws up the line feeds!
Also note that at some point whoever was working on optimizing the
FGTileMgr::Update also removed the bucket field from the FGLocation class.
This results in more calls to the tile scheduler. Not a big deal, but some
wasted cpu effort that could matter in certain situations.
Best,
Jim
Index: Scenery/tilemgr.cxx
===
RCS file: /var/cvs/FlightGear-0.9/FlightGear/src/Scenery/tilemgr.cxx,v
retrieving revision 1.12
diff -u -r1.12 tilemgr.cxx
--- Scenery/tilemgr.cxx 10 Dec 2002 20:50:52 - 1.12
+++ Scenery/tilemgr.cxx 10 Feb 2003 12:47:08 -
@@ -407,7 +407,7 @@
if ( longitude != last_longitude || latitude != last_latitude ) {
// update current elevation...
if ( updateCurrentElevAtPos( abs_pos_vector,
- globals-get_scenery()-get_center() ) )
+globals-get_scenery()-get_next_center() ) )
{
last_longitude = longitude;
last_latitude = latitude;
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Re: [Flightgear-devel] Ground elevation at an arbitrary point
On 12/16/02 at 12:07 PM David Luff wrote:
Some time ago (Sept/Oct) there was a long discussion about getting the
ground elevation at an arbitrary point which left me very confused after
reading it and didn't seem to come to any definate conclusion. What is
the
situation at the moment? Is there a function like
double GetGroundElev(Point3D lat_and_lon_of_somewhere)
anywhere which will return the ground elev if the appropriate tile is
already loaded and a distinctive value (-?) if the tile is not loaded?
Well, the fgCurrentElev(...) functions in hitlist.[ch]xx look promising,
but I might need a bit of help figuring out how to use them:
// Associated functions, assuming a wgs84 world with 0,0,0 at the
// center, find the current terrain intersection elevation for the
// point specified.
bool fgCurrentElev( sgdVec3 abs_view_pos,
sgdVec3 scenery_center,
ssgTransform *terra_transform,
FGHitList *hit_list,
double *terrain_elev,
double *radius,
double *normal );
bool fgCurrentElev( sgdVec3 abs_view_pos,
sgdVec3 scenery_center,
FGHitList *hit_list,
double *terrain_elev,
double *radius,
double *normal );
What does the scenery_center refer to? Is this the exact location at which
I receive the terrain_elev, or the center of the tile? What is the
abs_view_pos? Is this perhaps the point at which we get the elev, or is
this the direction vector in which we are looking? What is the hit_list
and can I ignore it - ie. just use a local one and discard it, eg:
{
FGHitList tempHitList;
bool haveIntersection = fgCurrentElev( ..., ..., tempHitList, ...,
..., ...);
}
or do I need to pay more attention to it? Lastly, what do the radius and
normal refer to - bounding sphere and normal of the specific intersected
polygon perhaps?
Sorry for all the questions at once - this is all a bit daunting to me and
I haven't poked my head into the 3D bits of Flightgear for a while.
Cheers - Dave
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Re: [Flightgear-devel] Ground elevation at an arbitrary point
David Luff [EMAIL PROTECTED] said: What does the scenery_center refer to? Is this the exact location at which I receive the terrain_elev, or the center of the tile? Neither actually, but it is a tile center. It is usually the center of the tile that the aircraft is currently located over. You're query location needs to be reasonably close to the scenery_center to get a good elevation. Depending on what you are doing (e.g. placing buildings) the the current FDM scenery_center is probably good enough. Take a look at the code under Tile Manager Updates to approx line 1200 in main.cxx, to see how the query works. Note that prep_ssg_nodes needs to be run to reallign the scenery vertices if you change the scenery center, before doing a query. What is the abs_view_pos? This is where you are. If I recall this is in geocentric coordinates. Same units as the scenery_center. or do I need to pay more attention to it? Lastly, what do the radius and normal refer to - bounding sphere and normal of the specific intersected polygon perhaps? IIRC the normal would be the straight down vector to the intersecting ground polygon. It seems to me that Norman recently made some changes that simplified what you are trying to do. Not sure if they are in CVS or not. There's a good chance you can use the same technique I used (see that main.cxx reference) depending on what you want to do. Just heed the comment around line 1227...the view location update/query needs to be done last before the rendering. Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Ground elevation at an arbitrary point
On 12/16/02 at 3:10 PM Jim Wilson wrote: David Luff [EMAIL PROTECTED] said: What does the scenery_center refer to? Is this the exact location at which I receive the terrain_elev, or the center of the tile? Neither actually, but it is a tile center. It is usually the center of the tile that the aircraft is currently located over. You're query location needs to be reasonably close to the scenery_center to get a good elevation. Depending on what you are doing (e.g. placing buildings) the the current FDM scenery_center is probably good enough. It's for the AI plane during taxiing and takeoff/landing run. In order to generate realistic radio traffic these may need to exist some distance from the fdm, but I guess that the rendering accuracy required decreases the further they are from the user. Going under the ground is not an option though if they are within sight of the user, unlike a building which may simply become less tall. Take a look at the code under Tile Manager Updates to approx line 1200 in main.cxx, to see how the query works. Note that prep_ssg_nodes needs to be run to reallign the scenery vertices if you change the scenery center, before doing a query. OK, I think I see what you're doing - changing the scenery center to the point of interest and then changing it back again when done. How expensive is this operation in the scheme of things - I see you do it every frame if the view location is different so I presume it can't be too bad? What is the abs_view_pos? This is where you are. If I recall this is in geocentric coordinates. Same units as the scenery_center. or do I need to pay more attention to it? Lastly, what do the radius and normal refer to - bounding sphere and normal of the specific intersected polygon perhaps? IIRC the normal would be the straight down vector to the intersecting ground polygon. It seems to me that Norman recently made some changes that simplified what you are trying to do. Not sure if they are in CVS or not. There's a good chance you can use the same technique I used (see that main.cxx reference) depending on what you want to do. Just heed the comment around line 1227...the view location update/query needs to be done last before the rendering. Thanks for the reply - I'll give it a go roughly along the lines of what you've done and see what happens! Cheers - Dave ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Ground Elevation
Sam Varner writes: How can I get the ground elevation and normal vector for a particular longitude and latitude? See Scenery / hitlist / hitlist.cxx / fgCurrentElev() Note this is very likely to change, but the API should stay the same These are available for the current FDM in the global Scenery instantiation see Scenery / scenery.hxx Cheers Norman ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Ground Elevation
Hi Sam: Not sure about the normal vector you mention, but as far as the ground elevation you can get that off of the charts (maps) provided by the U.S.G.S. For some areas there are CD ROMS available with (for example all the state of California as 7.5 min topo maps. The one that I have is from the National Geographic Society. (see http://www,topo.com for a very nice program! I use that program with FlightGear acting as a GPS reciever to get the airplane (simulator) location overlayed on the chart. A moving map display!!). jj Sam Varner wrote: How can I get the ground elevation and normal vector for a particular longitude and latitude? ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Ground Elevation
OOPS, had a typo in that link. (a , vice a .). Here's a better one anyway: http://maps.nationalgeographic.com/topo/gps.cfm jj jj wrote: snip The one that I have is from the National Geographic Society. (see http://www,topo.com snip ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Ground Elevation
On Tue, 2002-04-16 at 08:49, Norman Vine wrote: These are available for the current FDM in the global Scenery instantiation see Scenery / scenery.hxx This looks like what I need. (Thanks for your reply too, jj. I'm always up for cool map stuf:) One problem, I see a set_cur_normal(), but I don't see a get method. Am I missing something? ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
