On Wed, 15 Dec 2004 18:22:30 -0000 "Vivian Meazza" <[EMAIL PROTECTED]> wrote:
There are several points here.
1. The fact is that most 3d (I think all, but I haven't checked) rightly or wrongly already use normalized values. It would be a
significant task to change.
Agreed. This is a consideration. If the FDMs can divest themselves of the need to provide normalized values, I don't care what is done on the other side of FGInterface.
2. I don't think we tell YASim the correct angles to use. Therefore the normalized output, factored to produce the correct visual angles,
is the way to do it right now.
How does YASim know how far an aileron can deflect? How does FlightGear know how far to deflect the aileron? The FDM needs to know and use control surface deflection in degrees (or radians) - normalized values won't cut it for flight modeling. Since the FDM knows "truth", it can be the one-stop supplier for this angle - rather than normalizing it (based on what?) and shipping that to FlightGear/SimGear where it must be told how to de-normalize the normalized value for display.
3. For consistency, and remember that some 3d models are used with both YASim and other FDMs, we need normalized values.
This is just plain wrong. If an aircraft can deflect the elevator +/- 30 degrees that's the way it is. Regardless of FDM. We are talking about absolutes, here, not some arbitrary limit decided upon by the FDM. Even if the FDMs use different values for elevator deflection limits, the aircraft would fly based on the deflection actually made, and the 3D model will show what the FDM says it is flying to. Item #3 here is a non-issue.
4. It doesn't matter where the conversion is done. If FG is the only user of normalized values, it makes sense to do it there.
Yes, and that's my point. But there is a little more to it than that - it's about accuracy. If the FDMs abandon the provision of normalized values, what will FlightGear do with what is provided? If JSBSim sends FlightGear a 20 degree elevator deflection, what does it normalize that value based on? FlightGear will need to be provided with the maximum travel for aerosurfaces. Since teh FDM will also work with these maximums, this could introduce another "point of failure".
I have no doubt that this point was vigorously debated at some point in the past, and for good reasons we are where we are. We need to
revisit those discussions and revalidate the decisions before making
any change.
I would think we would have discussed this in the past, but I don't remember having done so. Normalized values were introduced in JSBSim about 2 years and 9 months ago, according to our CVS logs.
Best regards,
Jon
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