Re: [Flightgear-devel] c310 origin

[Jon S Berndt]

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 relative to the origin (if they
don't already); and

Isn't this the way it used to work? Or, how does it work, now? I think we track the initial CG, as well as the current CG.

2. add a couple of transforms to acmodel.cxx so that we use the CG as the centre of rotation.

This will be especially nice for modelling out-of-balance situations
(like 500lb of baggage in the back of a 172) -- everything will come
out looking right. It will also be valuable for aircraft that have
massive balance shifts, like a military aircraft dropping ordnance. I
don't expect that this will be a big job. What does everyone else
think?

Of course, the best way *is* to use the same origin for the FDM and the 3D model. If we all agree on an "FDM Frame", then we'll all know where the CG is if we report that number based on the FDM frame (and by FDM frame I mean the nose-tip thing we've been talking about). Euler angles from the FDM should be able to be used directly by the model rendering code I would think, instead of having to do rotations *and* translations for the 3D model if we have different frames of reference.

Jon

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