| Hi Tudor, 
re: 
> 1. after saving with annotations, reloading annotations will change positions !
 
There is a bug with the anchor point switching around when you save/reload annotation text block objects, it's fixed for the next beta.
 
> 2. crv - evaluateCurvature - understand it's trying to evaluate several connected control pts ?!?!?!
 
I'm not sure what you're asking here.
 
> 3. tg - evaluateTangent - shoudn't be perpedicular ?
 
No, a curve tangent is not perpendicular to a curve, it's the direction the curve is traveling in at that point, like this:
   
> 4. evaluateDerivatives - what are those ? (1,2,3 - too far away, pointed direction)
 
That would take a long time to explain, you could try some online descriptions like:
https://demonstrations.wolfram.com/TheDerivativeVectorsOfABSpline/ 
Or check out: 
"NURB Curves: A Guide for the Uninitiated" by Philip J. Schneider
https://vintageapple.org/develop/pdf/develop-25_9603_March_1996.pdf 
These values are vectors that represent directions, it maybe sounds like you're interpreting them as point location values instead of vector directions?
 
    - Michael |