Non-Monotone Key Frames

What are Non-Monotone Key Frames

Non-Monotone key frames are key frames where the key frame table is not in order. Here are some examples:

N1     ANGLE
0		50
50		270
100	230

This key frame table makes the angle of the needle increase as N1 goes up, but then the needle will reverse and go back down a bit. In this case, “angle” is non-monotone.

In this table for a a rotary;

enum   image
0		0
1		2
2		1
4		3
3		4

Both the input and output are non-monotone.

When Would I Want Non-Monotone Key Frames?

Generally you’ll want non-monotone key frames under two cases:

  1. If an instrument has to move forward and backward in response to data (e.g. the N1 needle example above).
  2. If you need to remap the enumerated values for a rotary (e..g the rotary example).

When Are Non-Monotone Key Frames Allowed?

  1. The value (but not dataref) key frame column can be non-monotone as long as the instrument reads but does not write the dataref. So non-monotone output can be used for a needle as long as it is not draggable, for example.
  2. Rotaries may have non-monotone key frames for both input and output, as long as values are matched _exactly_ without interpolation.

Previewing Non-Monotone Key Frames in Plane-Maker

Plane-maker recognizes that if you have out-of-order non-monotone key framing tables then you are probably intending to use a dataref that EXACTLY hits the key frame, like an int dataref that passes in enums. (You would use this to re-order the mapping between enums and rotary positions.)

In this case Plane-Maker will snap-round the simulated dataref to exact key frames so that you can see a sane preview of the dataref.

If you have done this but the dataref in x-plane is NOT rounded to key frames, you will then see wrong interpolation in x-plane, since we can’t cleanly interpolate non-monotone functions!!

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