Class AnimationKey

object --+
         |
        nuke.AnimationKey

A control point for an animation curve.
@var x
The horizontal position of the point
@var y
The vertical position of the point
@var lslope
The derivative to the left of the point. If interpolation does not have USER_SET_SLOPE then this may
not be correct until after evaluate() has been called.
@var rslope
The derivative to the right of the point. If interpolation does not have USER_SET_SLOPE then this may
not be correct until after evaluate() has been called.
@var la
The left 'bicubic' value. This represents the horizontal
position of the left bezier handle end, where 1.0 means 1/3 of the
distance to the previous point. If both handles for a span are 1.0
then the horizontal interpolation is linear and thus the vertical
interpolation a cubic function.  The legal values are 0 to
3. Setting outside of this range will produce undefined results.
@var ra
The right 'bicubic' value, again the legal range is 0 to 3.
@var interpolation
Used to calculate all the slopes except for the left slope of the first key and the right slope of the last key.
Legal values are:
- USER_SET_SLOPE : If this bit is on, the slopes are fixed by
the user and  interpolation and  extrapolation are ignored.
- CONSTANT: The value of the curve is equal to the y of the
point to the left.
- LINEAR: slopes point directly at the next key.
- SMOOTH: same as CATMULL_ROM but the slopes are clamped so that the convex-hull property is preserved (meaning no part of the
curve extends vertically outside the range of the keys on each side of it). This is the default.
- CATMULL_ROM: the slope at key n is set to the slope between
the control points n-1 and n+1. This is used by lots of software.
- CUBIC: The slope is calculated to the only cubic interpolation which makes the first and second derivatives
continuous. This type of interpolation was very popular in older animation software.  A different cubic interpolation is figured
out for each set of adjacent points with the CUBIC type.
- For the SMOOTH, CATMULL_ROM, and CUBIC interpolations, the first and last key have slopes calculated so that the second
derivative is zero at them.
@var extrapolation
Controls how to set the left slope of the first point and the right slope of the last point. Notice that this can
be set differently on the first and last points, and is also remembered on all internal points so if end points are deleted
old behavior is restored).
- CONSTANT: The left slope of the first point, and the right slope of the last point, are set to zero.
- LINEAR (and all other values): The left slope of the first point is set equal to it's right slope (calculated by the interpolation).
The right slope of the last point is set equal to it's left slope.
If there is only one point both slopes are set to zero.
@var selected
True if the point is selected in the curve editor.