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XML animation doubt

Xpand

Xpand

Messages
549
Country
nicaragua
Hi!
I have this problem that's been making me grind my teeth for a while:
So I have this part code that animates the nozzle of the plane when the side slip speed of the plane is greater than 2 radians per second:
<part>
<name>Slip_corrector</name>
<animation>
<parameter>
<code>
(A:Incidence beta, radian per second) 2 &gt;
if{ 100 }
els{ 0 }
</code>
<lag>35</lag>
</parameter>
</animation>
</part>
Click to expand...

I wanted to make the part work from frame 50 to 0 when the plane slides the tail left and from 50 to 100 when the tail slides right, but I can't seem to find a way to put two diferent values on the same part.
Can you help me please!?
Thanks!
 
Well, just like a rudder, you need to keyframe from 0 - 50 - 100, and then add an offset to your XML script, so that -50 = frame 0, 0 = frame 50, and 50 = frame 100:

Code: 
<code>
     50 (Some formula that will yield -50 to +50) +
</code>
 
Thanks!
But is that 50 an arbitrary value? Can't I put, for example "-2 to 2"?
 
Xpand said:
Thanks!
But is that 50 an arbitrary value? Can't I put, for example "-2 to 2"?
Click to expand...

You are dealing with two scales here:

1: from your "variable/formula"

2: the keyframes used

The task is to write your script such that it translates (scales) the "formula scale" to the "keyframe scale."

So, if you wanted to use "-2 to 2" yet keep the keyframes 0 - 50 - 100, then you simply need a "scalar" (multiplier) to convert one to the other...

Code: 
<code>
     50 (Some formula that will yield -2 to +2)  25 * +
</code>

So, now we are multiplying by 25 (our conversion scalar) then adding 50 (the offset) to the result:

Code: 
var * scalar + offset = keyframe

-2 * 25 + 50 = 0

0 * 25 + 50 = 50

2 * 25 + 50 = 100

If you wanted to keyframe from 0 - 20 - 40, then you'd need to calculate a new scalar + offset pair.

Is this beginning to make sense now? :D

In the FS9 SDK at the top of the makeMDL.parts.xml file ACES had comments that essentially stated this "conversion/scalar formula" but their terminology was just a bit different:

simvar * scale + bias

It took me a long time to realize that we aren't limited to using a pre-defined sim-variable, nor are we limited to the special <tags> they provided: <Scale> and <Bias>, but indeed we can use any bloody thing we want!
 
Last edited:
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