Jon Berndt wrote:
I mean no disrespect, nor do I question your ability. But, you don't
seem to entirely understand the power of the offsets property. If the
FDM reports a position, say the nose, as you intend to do. Now say that
the 3D model has the origin at the tail. All is not lost. As long as
someone can determine the deltas x,y,z between these two fixed points,
these deltas become the /offsets/ properties in the XML wrapper file that
tell the IG software how to shift the 3D model to the FDM's reported
position.
Yes. I agree with this. This is obvious -- sometimes we import 3D models made by others. I am not implying at all that the origin (0,0,0) must be the nose for 3D models (although it could be).
It didn't seem so obvious when you said this:
If we are providing the position of the nose, and the 3D model has some arbitrary origin (that's *not* the nose) then it's not gonna work.
In ths case calculate from the 3D model's origin to the nose and populate the /offsets/
property.
That JSBSim reported the nose is not significant.
Yes is it.
Because it must be understood what JSBSim is reporting:
Of course it must be understood what JSBSim is reporting. It must be understood what the
origin of the 3D model is. But it need not be the nose, nor must they be the same!
does the lat/lon/alt
reported by JSBSim to FlightGear represent the location of the tail, the
nose, the dynamic or empty-weight CG, or ... ? If this is standardized to a
commonly understood point, it makes it easier for newbies to relate 3D
models to the flight model. Otherwise, it will lead to confusion: how does a
newer or less capable user know what these offsets should be.
They would do like all newbies do in the open source world. The would read the
documents, look at the code, and ask questions in forums such as this. The FDM
reporting the nose as the position is not going to save them.
They would
have to dig into FlightGear / JSBSim documentation (with the associated
various degrees of completeness).
Like all good newbies do.
If referencing the empty weight CG, they
will have to research, or do trial and error, or do some math based on what
is in the config file.
Poor newbie. They might actually learn something... ;-)
It's easier to state that a physical and observable point is the reference point.
I absolutely agree. That really is the best arguement for using the nose. The only
problem with that is that even though it is physical and observable, it still might
not be agreed. There have been different viewpoints on what constitutes the nose
within just this thread! As I've said before, it will work, so do it.
It's fixed point to fixed point but they don't need to be the same fixed
point.
I've never said that the 3D model origin has to be the tip of the nose - in
fact I expect it NOT to be. This is where the offset file/properties comes
in.
Once again, you said:
If we are providing the position of the nose, and the 3D model has some arbitrary origin (that's *not* the nose) then it's not gonna work.
And you've said this kind of thing before in this thread. These kind of statements
I think are what is at the center of this disagreement. As long as you realise (and it
appears to me that you do) that the FDM's reported position does not need to be
the same as the origin of the 3D model.
But one must know what the "registration marks" are. I argue that for 3D model designers it is easier to identify the tip of the nose more accurately than where the empty weight CG is. And, it must be publicly announced just what the FDM is reporting for lat/lon/alt. This is what I mean by agreed-upon convention.
I am trying to preclude confusion amongst the audience of 3D modelers andThis is a false sense of security. Not all FDMs will use the nose, nor
flight model creators.
will all 3D models.
If all FDMs report the lat/lon/alt location of the same point, that will make things more "plug and play". Otherwise, the offset properties will need to be changed per FDM, per aircraft. A common VRP ought to make the aircraft models more interchangeable, without changing offset properties.
Althought I don't disagree, I don't see the problem. The /offsets/ properties are per FDM/
3D model anyway, are they not?
But, again, the 3D model does not need (and I don't expect it) to use the nose as the *origin*, it just has to HAVE a nose.
Okay.
-- Russ
Conway's Law: "The structure of a system tends to mirror the
structure of the group producing it."
-- Mel Conway Datamation (1968)_______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
