#120 Non-cockpit views jitter when FlightGear fdm is driven externally.

[Anonymous]

Originally created by: john.gri...@macb.com

What steps will reproduce the problem?
1.  Configure two networked computers in a master/slave configuration.

Slave System command line
./fgfs --aircraft=c172p --enable-ai-models --fdm=external --native-
fdm=socket,in,30,,5500,udp

Master System comman line
./fgfs --aircraft=c172p --enable-ai-models --native-fdm=socket,out,30,<ip
of slave system>,5500,udp

2.  On the slave system change the view to either chase, helicopter, chase
with w/o yaw, or model view.

3.  Start flying the master aircraft and observe the jittering in the
slave aircraft view.

What is the expected output? What do you see instead?

The expected output is a non-jittery view.  Instead we see a view that
seems to flip-flop between the correct view and a wrongly propagated view
thus causing the appearance of jitter.  In helicopter view, if your
velocity is sufficient, one of the flip-flop views will be of the aircraft
model rotated and pointing at you as if your point-of-view has changed. 

What version of the product are you using? On what operating system?

FlightGear 2.0.0, FlightGear 2.0.0 April 1, 2010 CVS with Bug 99 applied
(it did not fix this problem), and FlightGear 1.9.1.

Have seen this problem on Ubuntu 9.10, Ubuntu 9.04 and Windows XP (
FlightGear 1.9.1, have not tried FG 2.0.0 on XP yet)

Please provide any additional information below.

This does not seem to effect the cockpit view of the slave system.  This
has always been smooth.

[Anonymous]

Originally posted by: zakalawe@mac.com

Planning to take a look at this in May, but anyone else should feel free to try.

Labels: Network Nasal

[Anonymous]

Originally posted by: peter.server.homelinux.net@gmail.com

I can confirm this.
See http://www.youtube.com/watch?v=NfZvJ-WTTXg (skip to 2:40)

[Anonymous]

Originally posted by: john.gri...@macb.com

I think that the jitter seen by the copilot in external views mentioned in the Dual
Control wiki may be also related to this issue.

http://wiki.flightgear.org/index.php/Dual_control

[Anonymous]

Originally posted by: fabripa...@gmail.com

I can confirm also, I wrote a small piece of code to send UDP packet to FG to control the model, I thought my crappy code was the reason but now I see it's a bug.

Wrote this just to add that also "Tower view" and "Fly-by view" are smooth for me, jittering is appearing just in "Helicopter view", "Chase view" and "Chase view without yaw".

[Anonymous]

Originally posted by: d.v.razu...@gmail.com

Confirming that. Jitter appears when I'm using external fdm. Tried both the topicstarter's way and sending UDP packets from code. With that bug Flightgear cannot be used as a visualization, the view is awful.

There is NO such problem in flightgear 0.9.10 version.

[Anonymous]

Originally posted by: fabripa...@gmail.com

Edit: I'm using version 1.0.0

[Anonymous]

Originally posted by: xconspir...@gmail.com

The issue is still present in FG v2.0.0 on Windows XP, 32 bit, 3gb ram (PAE).

Flight Model

FDM: External
MOdel HZ: 30
Speed: 1
On Ground

Input/Output
Protocol: Native-fdm
Medium: Socket
Direction :in
Hz: 30
Hostname: (empty)
Port: 5500
UDP.

Aircraft which experienced problems:
Cessna 172P Skyhawk
Moyes Dragonfly
Beachcraft B1900D
A6M2 Zero (JSBSim)
A6M2 Zero

Most graphics and whatnot turned down to minimal.

Views affected in 172P: Fly-By, Cockpit, Helicopter, Chase, Tower, Chase cam without Yaw,

[Anonymous]

Originally posted by: rahulroy...@gmail.com

I am having the very same issue
I am not sure if related but some of the parameters in the property tree of the master do not get sent to the property tree of the slave instance.

Only cockpit view is usable in the slave instance
All other views jittery and unusable.

[Anonymous]

Originally posted by: bre...@gmail.com

(No comment was entered for this change.)

Status: Accepted

[Anonymous]

Originally posted by: cumuluni...@gmail.com

(No comment was entered for this change.)

Labels: Priority-Medium

[Anonymous]

Originally posted by: cumuluni...@gmail.com

I remember having seen the jitter on last year's FSweekend (Nov. 2010).
Just checked and don't see the jitter anymore.
Two instances of FG on the same machine with the exact cmd-line as in the original report. Just added a frame-rate-throttle of 20.

On Linux with git from today.
Gotta check, if the frame-rate-throttle plays a role here.

[Anonymous]

Originally posted by: cumuluni...@gmail.com

Works fine here, issue seems to be fixed.
Please reopen and provide a testcase if the issue persists for you.

Status: Expired