Create a tangent interpolator. A tangent interpolator allows to define
the behavior of an animation curve very precisely by defining the
tangents close to a key frame.
A tangent interpolator defines the behavior to the left and to the right
of a key frame, therefore it is only useful within a Timeline.
If used in a KeyFrame after a KeyFrame that has different interpolator,
it's treated as if the out-tangent of that KeyFrame was equal to the value in the KeyFrame.
The parameters define the tangent of the animation curve for the in tangent (before a key frame) and out tangent (after a key frame). Each tangent is specified with a pair, the distance to the key frame and the value of the tangent at this moment.
The interpolation then follows a bezier curve, with 2 control points defined by the specified tangent and positioned at 1/3 of the duration before the second KeyFrame or after the first KeyFrame. See the picture above.
t1
| The delta time of the in-tangent, relative to the KeyFrame | |
v1
| The value of the in-tangent | |
t2
| The delta time of the out-tangent, relative to the KeyFrame | |
v2
| The value of the out-tangent |