I am trying to mimic Maya's Graph Editior and I am using cubic hermite spline to interpolate between 2 points based off tangents that the user can manipulate manually. It looks okay but when I insert a point, the position of this new point appears to be correct but the new interpolation causes the spline to change shape. Anyone have any ideas?
Here is the algorithm I am using:
and I am using the derivative of this to calculate the slope of this new point.