The problem isn’t so much plotting the ellipse, we have that already. The problem is the tangent velocity at each point in the ellipse in order to give us the interpolation for a spline. We can’t plot hundreds of XYZ points to get the smoothness because the points themselves have to be replicated over network for clients to draw it (The clients are running on Android, and aren’t powerful enough to do the orbit math all the time).
So, we have to plot very few points and get the correct tangent to use at those points to get the correct interpolation. I’ve got the direction and velocity, but the strength of the tangent for the spline isn’t directly tied to the size of the velocity unfortunately, it also depends on how far around the spline the next point is by the looks of it. That’s where the difficulty comes from.
EDIT: Basically, there’s no easy pre-defined way to convert an Ellipse to a Bezier Curve.