Jon S Berndt wrote:
On Fri, 13 Feb 2004 14:33:43 -0700 Russell Suter <[EMAIL PROTECTED]> wrote:
Although I strongly agree that JSBSim reporting a fixed point relative to the aircraft is good, I'm not
particularly thrilled with the point you have chosen. I am more than happy to agree to disagree on that one though.
Just out of curiousity, which point would you favor -- given that we have multiple FDMs, and model various aircraft, for which there are various modelers who may have no clue about where the CG is?
Well, Jon, I think you already know the answer to that question. The way you phrase it though implies that I somehow
believe that the modeler (aka. graphic artist) must know where the CG is. That is not the case. But, I do believe it is better
to match the model to the FDM, and not the other way around. I also believe that the Image Generation software is the best
tool for the job. The IG already has the ability to translate the model anywhere. That's how it moves the model through the
scene. The IG has the ability to set viewpoint offsets from any reference point. That's how you can get certain chase views.
In fact, when you implement the VRP, I suspect some of these offsets (like the pilot's eyepoint) will need to be adjusted to
match the new reference location which will move forward significantly.
My preference is the empty weight CG. Every plane has one. It is aerodynamically significant. Its already tracked.
Its independent of any model. The method I've described previously doesn't require a modeler to model to that point
either. And, everything in the visual world can be made to effectively use it. In your example of the 747 model with
the A4 FDM, the 747 should appear to pitch about it's nose. If you switch them around, and have an A4 model with
a 747 FDM, it will appear that the model's pitch is significantly aft of the model -- like on being manipulated by a stick. If you used the empty weight CG, in both instances, the models would appear closer to normal.
-- 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
