Between YASim, JSBsim, and the U-3A 3d-model we've got three "origins" that
represent the approximate position of the aircraft. JSBsim is 0.2m higher
than the 3D model and YASim is 0.2m lower. It'd be nice if the two FDM's
agreed with each other, at least on the height above ground for the origi
Jim Wilson writes:
> Between YASim, JSBsim, and the U-3A 3d-model we've got three
> "origins" that represent the approximate position of the aircraft.
> JSBsim is 0.2m higher than the 3D model and YASim is 0.2m lower.
> It'd be nice if the two FDM's agreed with each other, at least on
> the h
> That's the hard part. The POH and the TCDS give the standard origin
> on the X axis (the weight and balance reference datum), and the origin
> on the Y axis can be assumed to be the centreline of the plane, but
> where do you put the Z origin? For a single, the thrustline of the
> propeller mig
Jon Berndt writes:
> > 1. Put the X axis origin at the published weight-and-balance reference
> >datum.
>
> 1) Respect the manufacturer's structural coordinates, if known. If not,
> place the X axis origin at the published weight and balance reference
> datum. If not known, place the X
On Fri, 13 Dec 2002 10:34:00 -0500,
David Megginson <[EMAIL PROTECTED]> wrote in message
<[EMAIL PROTECTED]>:
> Jon Berndt writes:
>
> > > 1. Put the X axis origin at the published weight-and-balance
> > > reference datum.
> >
> > 1) Respect the manufacturer's structural coordinates, if known.
David Megginson wrote:
> 1. Put the X axis origin at the published weight-and-balance reference
>datum.
> 2. Put the Y axis origin at the centreline of the plane.
> 3. Put the Z axis origin [where? the ground?].
I'll just state my opinion again, and then keep my head down until
someone tells m
This brings back the discussion a couple weeks ago on the 747 origin. The
following is what I got from that thread:
1). The reported "origin" is arbitrary in relation to the FDM's internal
workings...ie how pitch/roll/yaw is calculated. The exact position of the 3D
model origin can be calculated
Andy Ross writes:
> Whatever convention we pick should be an easily explainable and
> identifiable from the *shape* of the airframe only. Not everyone
> has a POH handy, very few people have W&B or C.G. numbers, and even
> things like the centerline are subject to argument on some
> aircraft
On Fri, 13 Dec 2002 10:09:06 -0800
Andy Ross <[EMAIL PROTECTED]> wrote:
Whatever convention we pick should be an easily explainable and
identifiable from the *shape* of the airframe only. Not everyone has
a POH handy, very few people have W&B or C.G. numbers, and even things
like the centerline
Jim Wilson writes:
> 2). On a fixed wing aircraft, if origin is anywhere but between the
> wings the external model views that follow along with the aircraft
> (e.g. chase view) will not look correct. The camera is tied to the
> origin. If the origin is at the nose or tail then the plane
>
David Megginson <[EMAIL PROTECTED]> said:
> Jim Wilson writes:
>
> > 2). On a fixed wing aircraft, if origin is anywhere but between the
> > wings the external model views that follow along with the aircraft
> > (e.g. chase view) will not look correct. The camera is tied to the
> > origin.
David Megginson writes:
> Jim Wilson writes:
>
> > 2). On a fixed wing aircraft, if origin is anywhere but between the
> > wings the external model views that follow along with the aircraft
> > (e.g. chase view) will not look correct. The camera is tied to the
> > origin. If the origin is a
On Fri, 13 Dec 2002 13:45:11 -0500
David Megginson <[EMAIL PROTECTED]> wrote:
OK, finally I understand the problem. What we need to do, then, is
apply the euler angles to the CG rather than the origin when rotating
the 3D model. We need only two steps:
1. have the FDMs report the current CG r
Jim Wilson writes:
> Actually, no, well yes this is a good idea. But I don't think it is
> necessary. AFAIK the model rotates correctly already.
The FDMs give us lon/lat/alt and roll/pitch/hdg. FlightGear then has
to apply transformations to make the model appear in the right place
and with
--- David Megginson <[EMAIL PROTECTED]> wrote:
> Jim Wilson writes:
>
> > 2). On a fixed wing aircraft, if origin is anywhere but between
> the
> > wings the external model views that follow along with the aircraft
> > (e.g. chase view) will not look correct. The camera is tied to
> the
> >
--- Jon S Berndt <[EMAIL PROTECTED]> wrote:
> On Fri, 13 Dec 2002 13:45:11 -0500
> David Megginson <[EMAIL PROTECTED]> wrote:
>
> >OK, finally I understand the problem. What we need to do, then, is
> >apply the euler angles to the CG rather than the origin when
> rotating
> >the 3D model. We
--- Norman Vine <[EMAIL PROTECTED]> wrote:
> David Megginson writes:
>
> > Jim Wilson writes:
> >
> > > 2). On a fixed wing aircraft, if origin is anywhere but between
> the
> > > wings the external model views that follow along with the
> aircraft
> > > (e.g. chase view) will not look correc
On Fri, 13 Dec 2002 12:09:34 -0800 (PST)
Tony Peden <[EMAIL PROTECTED]> wrote:
I think it's pretty clear that we aren't going to agree on one
coordinate system to use.
Aside from that, agreeing on one takes away the freedom to choose a
location that makes sense for the aircraft you are workin
On Fri, 13 Dec 2002 14:56:39 -0500
David Megginson <[EMAIL PROTECTED]> wrote:
Jim Wilson writes:
> Actually, no, well yes this is a good idea. But I don't think it is
> necessary. AFAIK the model rotates correctly already.
If you are rotating the model in the same order as the
FDM, then t
Tony Peden writes:
> Since this makes the 3D modeler's choice independent of the FDM
> modeler's choice, it seems the most sensible to me.
That wasn't my intention -- you'd still need the same origin for this
to work. It's just a way for the 3D engine to know what point to
pivot the model ar
David Megginson writes:
> Jim Wilson writes:
>
> > Actually, no, well yes this is a good idea. But I don't think it is
> > necessary. AFAIK the model rotates correctly already.
>
> The FDMs give us lon/lat/alt and roll/pitch/hdg. FlightGear then has
> to apply transformations to make the mo
David Megginson <[EMAIL PROTECTED]> said:
> Jim Wilson writes:
>
> > Actually, no, well yes this is a good idea. But I don't think it is
> > necessary. AFAIK the model rotates correctly already.
>
> The FDMs give us lon/lat/alt and roll/pitch/hdg. FlightGear then has
> to apply transformati
On Fri, 2002-12-13 at 12:40, Jon S Berndt wrote:
> On Fri, 13 Dec 2002 12:09:34 -0800 (PST)
> Tony Peden <[EMAIL PROTECTED]> wrote:
>
> >I think it's pretty clear that we aren't going to agree on one
> >coordinate system to use.
> >
> >Aside from that, agreeing on one takes away the freedom to
Tony Peden writes:
> On Fri, 2002-12-13 at 12:40, Jon S Berndt
> > >I think it's pretty clear that we aren't going to agree on one
> > >coordinate system to use.
> > >
> > >Aside from that, agreeing on one takes away the freedom to choose a
> > >location that makes sense for the aircraft you a
On 13 Dec 2002 15:22:38 -0800
Tony Peden <[EMAIL PROTECTED]> wrote:
What I'm proposing is that we don't have to agree to use
the same point.
We just need to provide a way to correct for the
difference.
Ah, yes. We will need to provide another point - location
of nose tip (or whatever). In in
Jim Wilson writes:
>
> This same effect is less or more depending on exactly where the "origin" is.
> We could eliminate it by offseting the lon/lat/alt and roll/pitch/hdg to the
> current center of gravity for the camera, but that isn't necessary. It'll
> look good enough (you can't visually se
David Megginson wrote:
OK, finally I understand the problem. What we need to do, then, is
apply the euler angles to the CG rather than the origin when rotating
the 3D model. We need only two steps:
1. have the FDMs report the current CG relative to the origin (if they
don't already); and
2
Norman Vine <[EMAIL PROTECTED]> said:
> In your example you may not see the error but .
What I meant was that offseting to the varible center of gravity wouldn't be
visible either outside or inside the aircraft. The FDM already provides the
attitude effects, it is the change in axes that wou
> IMHO it'd make the most sense to put the offset (from the nose or
> tail) to the
> 3D model origin location into the FDM's aircraft config xml file. This
> location should be on the leading edge of the wings and z axis
> centered on the
> nose as described above. The 3D modeler's could refer t
On Sat, 2002-12-14 at 07:26, Jon Berndt wrote:
> > IMHO it'd make the most sense to put the offset (from the nose or
> > tail) to the
> > 3D model origin location into the FDM's aircraft config xml file. This
> > location should be on the leading edge of the wings and z axis
> > centered on the
>
Jim Wilson writes:
> Norman Vine <[EMAIL PROTECTED]> said:
>
> > In your example you may not see the error but .
>
> What I meant was that offseting to the varible center of gravity wouldn't be
> visible either outside or inside the aircraft. The FDM already provides the
> attitude effects,
Tony wrote:
> Are we sure we want to put the 3D model origin to cg offsets in the FDM
> config file. IIRC, having multiple 3D models for any one aero model is
> pretty standard fare in the MSFS world.
The only thing we'd do different in JSBSim is to say where the nose/prop
tip is. This would giv
Jon Berndt <[EMAIL PROTECTED]> said:
> > IMHO it'd make the most sense to put the offset (from the nose or
> > tail) to the
> > 3D model origin location into the FDM's aircraft config xml file. This
> > location should be on the leading edge of the wings and z axis
> > centered on the
> > nose a
Jon Berndt <[EMAIL PROTECTED]> said:
> Tony wrote:
>
> > Are we sure we want to put the 3D model origin to cg offsets in the FDM
> > config file. IIRC, having multiple 3D models for any one aero model is
> > pretty standard fare in the MSFS world.
>
> The only thing we'd do different in JSBSim
> Really we just need the FDMs to agree on something. Or maybe
> not...maybe the
> idea of sharing 3DModel configs between FDMs (c310-jsbsim,
> c310-yasim pointing
> to the same model.xml) is impratical or too complex? Certainly if one
FDM
> models gear compression and the other doesn't, that is
Jon Berndt <[EMAIL PROTECTED]> said:
> It's neither impractical nor complex. FWIW, there really is a standard
> already out there, and we use it. That is, the structural frame, as I have
> outlined before. The only problem I see is that the FDM and the 3D model
> rendering code need to have a stat
> Yes, I knew this would sound a little complicated with swept,delta,body
wing
> aircraft. But making it the nose really just puts the decision on to
the 3D
> Modeler where to some degree the flight model designer could have a
better
> idea. Isn't there some way of deriving an average or nominal
Jon Berndt <[EMAIL PROTECTED]> said:
> I don't really think that the CG (or anything like it) should have
> anything to do with a common reference point. I think it should be
> something you can readily see. The nose/prop hub tip is about as
> unambiguous as it gets. Due to the nature of defining
Jon Berndt <[EMAIL PROTECTED]> said:
> I have seen posts to the effect that there IS a problem with properly
> communicating the origin, and that this problem deals with rotating the 3D
> model as specified by the FDM Euler angles, but NOT accounting for the
> fact that the FDM assumes rotation ab
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