Hi pafurijaz,
re:
> About the approximation I have read this here on wikipedia. but maybe I've haven't
> read all the paragraph, only the first part.
Right, it says this:
quote:
"Non-rational splines or Bézier curves may approximate a circle, but they cannot represent it exactly. Rational splines can represent any conic section, including the circle, exactly."
Non-rational splines, meaning a spline type without weight values in addition to x,y,z values for every control point, can only approximate a circle. That's why a NURBS curve is not a non-rational spline, the R in NURBS is for Rational.
As it says in the 2nd sentence, Rational splines (which includes NURBS) can represent circles exactly.
The Bezier curves in 2D illustration programs like Adobe Illustrator are non-rational cubics and can only approximate circles, unlike NURBS which can represent circles exactly.
re: AutoCAD radius dimension on spline
I don't have a running copy here at the moment but no I don't think that is correct:
https://forums.autodesk.com/t5/autocad-2000-2000i-2002-archive/radius-dimension-of-a-spline/td-p/1773056
https://www.cadforum.cz/en/how-to-dimension-radius-and-center-of-a-spline-in-a-given-point-tip12282
> And this image is on FreeCad and show the curvature normal on B-spline and is possible to
> get the visualization of this on Moi3d maybe with a script?
Sorry no MoI doesn't currently have a function for visualizing the curvature graph. It is possible for scripts to evaluate curvature properties of curves now so a script could be possible but I don't know if there is one.
- Michael
