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
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
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 to
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
nose as
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, it is
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 give
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 as described
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 is to say
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 an
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 static
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 the
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 height
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 might
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 axis
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. If
not,
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 me
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 WB 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 WB 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. If the
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 at the
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
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
origin. If
--- 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 need only two
--- 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 correct. The camera is
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 working
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 the
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
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 model
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 transformations to
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 choose a
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 are working on
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
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 see the
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
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