Hi Karsten, great job so far!

> Can I get a tangent-vector from a curve on a special point or points of curve
> to calculate it approx by script, without arraycurve-factories?

Sorry no unfortunately there isn't any methods set up currently for scripts to evaluate properties of curves like tangent vectors at arbitrary points.

That is something that I want to add in the future - right now the scripting in MoI is not focused on doing heavy duty calculations inside of a script, the scripting is primarily used at this time as a kind of control flow mechanism that handles hiding/showing UI, creating picking mechanisms, things like that. So it's currently missing a lot of stuff that would be useful for more detailed calculations like you're trying to do here.

In the future I definitely want to make that sort of thing more feasible to do in script.

- Michael