On Apr 17, 2008, at 3:05 PM, Adam Dershowitz wrote: > I am driving FlightGear with a text file of data. For some reason, > when I am looking at an external view, for each altitude change there > is an annoying flash. It looks like a single frame being drawn in the > wrong position. I can sometimes make out a ghost of the airplane > being drawn in the wrong place, or the ground in the wrong place. > This doesn't happen with an internal view. Even altitude changes in > the data file of less than 50 ft. are enough to cause it to happen. > > I am using version 1.0, plib on a Mac. > > Any idea why this is happening or what I can do about it? It makes > this playback look really bad. > > Thanks much. > > > --Adam > >
I found that the problem doesn't actually relate to using the text file. If I just start FG with a null fdm then use the http interface to change the altitude I get the same annoying flash. For example if I do this: fgfs --httpd=5432 --fdm=null --prop:/sim/current-view/view-number=2 --timeofday=noon then I go and use my web browser to change the altitude by 50 ft there is a flash during this redraw, and it is worse with a larger altitude change. The problem is more obvious at higher altitudes because a small change in altitude is not really visible as a change in view. So, for example, doing the above, then changing the altitude to 2000 ft, then stepping it to 2050 the flash is very visible. I also just tried the above with the OSG version (I downloaded the binary from macflightgear) and I get the same results. The details seem to depend on the particular view that is being used. But from some cameras, it appears that there is a flash of the aircraft from a different perspective, or it has a different attitude, for perhaps a single frame. With no other FDM, or other inputs, it seems that the attitude should not change at all. I also tried doing small changes in latitude and it has the same effect. At 2000 ft, with a null FDM, a small change in latitude, makes the image snap to the side and back. So to the eye the initial and final frames look the same, but there is a jolt that looks almost like someone smacked the "virtual camera" and it jumps for a frame and then comes right back. I also tested some aircraft attitude changes and it does NOT happen with them. Even for large changes (heading changes of 180 degrees, pitch 90 degrees) the aircraft is just smoothly redrawn. Is there something odd about how the camera location is calculated and changed, with a change in altitude? Is FG using some other vehicle rates, or something, to do some of the drawing so that having 0 rates and a step change confused it for a frame? Is there something flakey about video card or driver? (I am using a Macbook Pro that has an AY, Radeon X1600) I am pretty baffled by this. Thanks, --Adam ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
