Custom keytrack interpolant

Hello,

I am having issue creating a custom Interpolant for my vectorKeyFrameTrack, the effect i want to achieve can be seen with the second cube which is animated using createjs tween. added a sandbox

https://codesandbox.io/p/sandbox/affectionate-flower-72drzh?file=%2Fsrc%2Findex.mjs%3A49%2C5

codesandbox

Anyone? :smiling_face_with_tear: