Lee Elliott wrote:
> Sent: Friday, September 17, 2004 9:57 PM > To: FlightGear developers discussions > Subject: Re: [Flightgear-devel] Problem with ballistic sub-model > > > On Friday 17 September 2004 16:09, Vivian Meazza wrote: > > Arnt Karlsen wrote: > > > Sent: Friday, September 17, 2004 10:03 AM > > > To: FlightGear developers discussions > > > Subject: Re: [Flightgear-devel] Problem with ballistic sub-model > > > > > > > > > On Fri, 17 Sep 2004 07:56:42 +0100, Vivian wrote in message > > > > > > <[EMAIL PROTECTED]>: > > > > Ampere K. Hardraade wrote > > > > > > > > > Sent: Thursday, September 16, 2004 7:12 PM > > > > > To: FlightGear developers discussions > > > > > Subject: Re: [Flightgear-devel] Problem with > ballistic sub-model > > > > > > > > > > On September 16, 2004 01:08 pm, Vivian Meazza wrote: > > > > > > There are some other basic shortcomings as well: > the submodel > > > > > > doesn't inherit the parent accelerations, or the velocities > > > > > > and accelerations due to roll, pitch and yaw. Only release > > > > > > droptanks > > > > > > > > > when flying straight and level > > > > > > ..uh, in the real world, this is possible if not > permissible, with > > > fun consequences like one or more hard points releases jammed for > > > at least a while etc. > > > > > > > > They shouldn't inherit accelerations. > > > > > > > > Quite right - they shouldn't. I was getting over > > > > > > enthusiastic there, > > > > > > > and forgetting my Newtonian physics. > > > > > > ..don't worry, there is also Murphy law physics. ;-) > > > > Right, back to Newton :-). I think I've solved the problem. Mixing > > elevation up = positive with speed down = positive nearly made my > > brain blow a fuse > > > > I had to reverse a number of signs to get it right. I took the > > opportunity to add roll to the submodel so that droptanks will come > > off with the right orientation. I not yet added either the parent > > rotational speed to the submodel, or yaw, so if you release > droptanks > > with significant roll rate or yaw angle on the aircraft the > submodel > > will not be quite right. Straight and level, or nearly so, is fine. > > > > I've asked Erik to upload the modified files to CVS. It looks OK on > > the Hunter, but perhaps Lee could give the revised submodel a good > > test. > > > > Regards > > > > Vivian > > Hello Vivian, > > I just updated from cvs, including updates to the sub-model > stuff and while > the pitch of the sub-model seems fixed ok, I'm still not able > to get the > speed right. I tried reducing the <eda> setting to a very low value > (0.0000001) and then 0 but the velocity of the sub-model > always seems to be > zero. > > As an experiment I tried setting some +ve <speed> values i.e. > 10 & 1000 but > still got a zero sub-model speed - I tested this by > 'releasing' the bomb > (bearing in mind I have <repeat> and unlimited models set for > de-bugging > purposes) while sitting on the runway. Instead of a stream > of sub-models > moving forward away from the stationary a/c they remain at > the origin. If I > then accelerate the a/c I leave a trail of sub-models behind me. > > There's an archive of the a/c at > > http://www.overthetop.freeserve.co.uk/EE-Canberra-20040916.tar.gz > > ...if you want to have a look. The release keyboard mapping has been > commented out in the ~set.xml file. > Like the model: up to your usual standard. (Well, all except the pilot's bone dome - wrong pattern :-)) It works. The operative word is 'accelerate'. As you accelerate you leave bombs behind: they are instantiated with the velocity at the time of release, but since the aircraft is accelerating it will be left behind. Try the following using your original values in submodel: Release a bomb while stationary: it turns and aligns with the velocity - note although the aircraft is stationary, there are still some small N/E/D velocities. I'm not sure why. Accelerate down the runway: the bombs gradually align with the aircraft as forward motion is added, but they are left behind. Brake: the bombs shoot ahead of the aircraft, with their proper velocity. All those left behind now go past. Great fun - like big fish swimming by. I've convinced myself, anyway - Newton's Laws of Motion at work (see Arnt's comments). Regards Vivian _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
