Re: [Flightgear-devel] Bouncing JSBSim aircraft
On 11/28/2010 2:41 PM, Gijs de Rooy wrote: Yeah, problems is fixed! I had --model-hz=30. Setting it to 120 (so it was omitted from the commandline by FGRun) fixed the problem. For what it's worth (I do think it is weird that some aircraft are not affected by low model-hz, while others are), some more info below: Bertrand wrote: Since I am mostly involved in the landing gears code of JSBSim, I would be interested in having more details about the problem you experienced. After takeoff, bouncing stops. After landing, bouncing continues. When braking, the intensity of the bounces increases significantly. Apparently not all JSBSim aircraft bounce (see list below). There are three categories of bouncing to be distincted: ** *No bouncing:* 737-300 (J) 777-200ER (Y) Storch (J) F-117 (J) *Small bouncing: *b1900d (J) Bravo (J) ercoupe (J) followme (J) *Extreme bouncing: *747-400 (J) c172p (J) Cheers and thanks for the help! Gijs If I recall correctly, we had a similar problem 3 or 4 years ago that only showed up on Windows builds. It had to do with uninitialized variables that happened to be set to 0 on Linux (gcc) builds and random stuff on Windows (MSVC++) builds. Could be a similar problem this time? -Reagan -- Increase Visibility of Your 3D Game App Earn a Chance To Win $500! Tap into the largest installed PC base get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Bouncing JSBSim aircraft
On Monday 29 November 2010 12:59:26 Reagan Thomas wrote: If I recall correctly, we had a similar problem 3 or 4 years ago that only showed up on Windows builds. It had to do with uninitialized variables that happened to be set to 0 on Linux (gcc) builds and random stuff on Windows (MSVC++) builds. Could be a similar problem this time? -Reagan Gijs already confessed that he changed the model-hz to 30Hz. The gear model code just isn't robust enough to take a large transient at that low a frequency. When flightgear starts, it places the aircraft above the scenery and lets it drop. At the normal model-hz (120Hz) the gear model does a good job of absorbing this impact, but as the frequency drops quantization errors cause the gear model to misbehave. Ron -- Increase Visibility of Your 3D Game App Earn a Chance To Win $500! Tap into the largest installed PC base get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
[Flightgear-devel] Bouncing JSBSim aircraft
Hi all, after updating fgdata from Gitorious this evening and installing the win32 nightly binary from Hudson (28-nov-2010 7:00:55), JSBSim aircraft suddenly bounce, when at the ground. Some aircraft bounce more than others (747-400 and C172P for example crash due to the extreme forces), while the followme car only bounces up and down a little. I was able to drive around normally (apart from the bouncing) with the followme. So it looks like it depends on the gear compression/spring settings of the aircraft being operated. The YASim aircraft I tried did not show this behaviour. I suspect the problem arised after this commit by Erik: http://www.gitorious.org/fg/flightgear/commit/ad51a9bde2995605984161af1b4273b28ce4fddc Any clue on what's wrong? Can anyone confirm this behaviour? Cheers, Gijs -- Increase Visibility of Your 3D Game App Earn a Chance To Win $500! Tap into the largest installed PC base get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Bouncing JSBSim aircraft
2010/11/28 Gijs de Rooy gijsr...@hotmail.com: Hi all, after updating fgdata from Gitorious this evening and installing the win32 nightly binary from Hudson (28-nov-2010 7:00:55), JSBSim aircraft suddenly bounce, when at the ground. Some aircraft bounce more than others (747-400 and C172P for example crash due to the extreme forces), while the followme car only bounces up and down a little. I was able to drive around normally (apart from the bouncing) with the followme. So it looks like it depends on the gear compression/spring settings of the aircraft being operated. The YASim aircraft I tried did not show this behaviour. I suspect the problem arised after this commit by Erik: http://www.gitorious.org/fg/flightgear/commit/ad51a9bde2995605984161af1b4273b28ce4fddc Any clue on what's wrong? Can anyone confirm this behaviour? Cheers, Gijs Hi Gijs, I could not reproduce the problem you described. Tested last git revision for SimGear (1cb8f9237cb7fa47eb8e4a89f135ac17656315a5), FlightGear (1cf207e0540712d3344c48f936a7aade3c5c2797) and data (115032a7c5828c7e82462ca8e57ab0be444d4120). I tried the following commands fgfs --fg-root=/path/to/my/copy/of/fgdata and fgfs --aircraft=747-400 --fg-root=/path/to/my/copy/of/fgdata AFAICT, these are supposed to run the C172P and 747-400. I played a bit with the Cessna (taxiing, taking-off, landing, hard landing, ...) and it behaved correctly. Since I cannot pilot the 747-400, I taxied it a bit and took off and everything went well (well, except that I crashed it while trying to land it). Since I am mostly involved in the landing gears code of JSBSim, I would be interested in having more details about the problem you experienced. Cheers, Bertrand. -- Increase Visibility of Your 3D Game App Earn a Chance To Win $500! Tap into the largest installed PC base get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Bouncing JSBSim aircraft
There was an update to the gear code yesterday. I suppose it's possible that the new update has side effects. We'll look into it. Does anyone know when the last good code is dated? Jon Sent from my Samsung Captivate(tm) on ATT Gijs de Rooy gijsr...@hotmail.com wrote: Hi all, after updating fgdata from Gitorious this evening and installing the win32 nightly binary from Hudson (28-nov-2010 7:00:55), JSBSim aircraft suddenly bounce, when at the ground. Some aircraft bounce more than others (747-400 and C172P for example crash due to the extreme forces), while the followme car only bounces up and down a little. I was able to drive around normally (apart from the bouncing) with the followme. So it looks like it depends on the gear compression/spring settings of the aircraft being operated. The YASim aircraft I tried did not show this behaviour. I suspect the problem arised after this commit by Erik: http://www.gitorious.org/fg/flightgear/commit/ad51a9bde2995605984161af1b4273b28ce4fddc Any clue on what's wrong? Can anyone confirm this behaviour? Cheers, Gijs -- Increase Visibility of Your 3D Game App Earn a Chance To Win $500! Tap into the largest installed PC base get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel -- Increase Visibility of Your 3D Game App Earn a Chance To Win $500! Tap into the largest installed PC base get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Bouncing JSBSim aircraft
Yeah, problems is fixed! I had --model-hz=30. Setting it to 120 (so it was omitted from the commandline by FGRun) fixed the problem. For what it's worth (I do think it is weird that some aircraft are not affected by low model-hz, while others are), some more info below: Bertrand wrote: Since I am mostly involved in the landing gears code of JSBSim, I would be interested in having more details about the problem you experienced. After takeoff, bouncing stops. After landing, bouncing continues. When braking, the intensity of the bounces increases significantly. Apparently not all JSBSim aircraft bounce (see list below). There are three categories of bouncing to be distincted: No bouncing: 737-300 (J) 777-200ER (Y) Storch (J) F-117 (J) Small bouncing: b1900d (J) Bravo (J) ercoupe (J) followme (J) Extreme bouncing: 747-400 (J) c172p (J) Cheers and thanks for the help! Gijs -- Increase Visibility of Your 3D Game App Earn a Chance To Win $500! Tap into the largest installed PC base get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Bouncing JSBSim aircraft
2010/11/28 Gijs de Rooy gijsr...@hotmail.com: Yeah, problems is fixed! I had --model-hz=30. Setting it to 120 (so it was omitted from the commandline by FGRun) fixed the problem. (...snip...) After takeoff, bouncing stops. After landing, bouncing continues. When braking, the intensity of the bounces increases significantly. Apparently not all JSBSim aircraft bounce (see list below). To make a long story short, this kind of behaviour is driven by the eigenfrequencies of the system. They are the frequencies at which a system naturally oscillates. A very rough estimate of these frequencies can be obtained by the square root of k/m where k is the sum of the stiffnesses of all the gears and m is the mass of the airplane. It is thus obvious that this frequency varies from one airplane to the other. As far as I remember, the simulation rate must be as greater as possible than these frequencies otherwise bouncing issues may arise. Hence the disappearance of the issue when you set the simulation time rate back to its default 120 Hz. Cheers and thanks for the help! You are welcome :-) Cheers, Bertrand. -- Increase Visibility of Your 3D Game App Earn a Chance To Win $500! Tap into the largest installed PC base get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
