Hi Andrei,

> also where i can read about this knots I hear about it often when watch rhino
> tutorials, and kinks if im not wrong.
> And also in rhino normal direction means, but in moi i never meat problem
> with this, what is the answer)?

MoI is designed to try and minimize the need to understand every single technical detail of NURBS modeling.

"Knots" are one of the pieces of information that make up NURBS curves and surfaces - every surface is made up of a set of points, weights, a degree value, and a knot vector, not just only a set of points alone.

The knot vector tends to be one of the more difficult pieces to describe very well - it's related to the number of "spans" of the curve or surface. Each span is sort of like an internal segment of the curve and the knots are where the spans touch each other.

Check out here if you want an in depth technical description of all the details of NURBS mathematics:

http://www.mactech.com/articles/develop/issue_25/schneider.html
http://web.cs.wpi.edu/~matt/courses/cs563/talks/nurbs.html
http://www.rhino3d.com/nurbs

- Michael