On 02/25/2010 02:26 PM, Grimes, John R Mr CTR USAF AFMC AFRL/RWGG wrote: > I am currently running FlightGear 2.0.0 (snagged from the ibiblio ftp > site) that I compiled on my Ubuntu 9.10 64 bit system. Compiled up no > problem, but I have noticed that when I attempt to setup a master/slave > scenario that I get some odd artifacts on slave display. The scene on > the slave looks as if the position of the aircraft is lagged behind, and > then it suddenly tries to jump to the correct location.
It's a bug. Actually at least five bugs. > These artifacts > don't seem to appear in cockpit view or tower view, but they make all > the other views almost unusable. Yes. > I have checked the developers lists, > and I have seen people mention problems similar to this, but nobody > seems to have a good solution. I assume you found the threads on --[Flightgear-devel] multiple --generic record/playback errors --[Flightgear-devel] null-FDM and UFO-FDM instrument outages Note that the "external" FDM is a synonym for "null" FDM. > It could be a double precision problem, There are at leaast two such double precision / float / roundoff bugs, although perhaps only one is biting you at the moment since you are using the "udp" protocol. So far I have -- patched the "playback" protocol, -- patched io/sg_file.cxx, -- patched generic.cxx, and -- patched some of the aircraft's nasal files... ... which solves some of the shudder and jitter problems but not all, especially not in the non-cockpit views. http://gitorious.org/~jsd/fg/sport-model/commits/sport http://gitorious.org/~jsd/fg/sport-simgear/commits/sport > or it could be the FG is propagating the view forward by a certain > amount of time and correcting the view when a new frame of data comes > in. Something like that wouldn't surprise me. > Here is the master system's command line I am using. <snip> Thanks for the detailed, professional bug report.... ================= If you want to pursue it, please go ahead. You won't be duplicating any effort of mine, because I'm kinda busy at the moment. I doubt I will have large amounts of time to devote to this set of bugs in the next week or so ... but feel free to ask questions. Suggestion: A majority of the jitter / shudder in non-cockpit views is readily observable with the ascii "playback" protocol, not just with the binary "udp" protocol. And I got as far as fixing gs_file.cxx so that it can read from a named pipe (FIFO) which I reckon might make the debugging faster and easier..... Suggestion: Scrutinize the console log for Nasal error messages. If you see something about "nil used in numeric context" then some .nas file somewhere is referencing a variable that is not being set by the FDM. Bear in mind that this is treated as a serious error, and defeats all the functionality in that .nas file. Such things are easy to fix; in particular, for the default c172p, the following patch helps a lot: diff --git a/Aircraft/c172p/Nasal/action-sim.nas b/Aircraft/c172p/Nasal/action-sim.nas index 7e79f51..d5defe3 100644 --- a/Aircraft/c172p/Nasal/action-sim.nas +++ b/Aircraft/c172p/Nasal/action-sim.nas @@ -26,6 +26,11 @@ var panelLights = props.globals.getNode("controls/lighting/panel-norm", 1); var dhN_ft = props.globals.getNode("gear/gear[0]/compression-ft", 1); var dhR_ft = props.globals.getNode("gear/gear[2]/compression-ft", 1); var dhL_ft = props.globals.getNode("gear/gear[1]/compression-ft", 1); + +dhN_ft.setDoubleValue(dhN_ft.getValue() or 0); +dhR_ft.setDoubleValue(dhR_ft.getValue() or 0); +dhL_ft.setDoubleValue(dhL_ft.getValue() or 0); + var propGear0 = props.globals.getNode("gear/gear[0]", 1); var propGear1 = props.globals.getNode("gear/gear[1]", 1); var propGear2 = props.globals.getNode("gear/gear[2]", 1); ... or you could patch the protocol to set a fuller set of variables ... or both. ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
