In commit 8d2b00a06af31afaac35e229a32845540050b3ca
example CurveSplit.py a Bezier can be split at values of parameter t. That's good, but how to know what is what value of t which corresponds to a curvilinear distance if there is not a .atLength() method defined  for Bezier?

1) ok relative length only
2) I do not agree with limitation to Polyline because of one reason: in order to compute the 'exact' length on a generic curve there are equations/integrals which, if I remember well, need to be solved numerically because do not have analytical solution:
the relation between the curve parameter 't' and the curvilinear distance L has not an analytical solution.
So solving numerically the equation or approximating the polyline with an arbitrary number of points in my opinion is the same.
That's why I would generalize to Curve.splitAtLength and expose the 'npre' parameter to the user to control the accuracy. Later, the user could choose to use either the 'npre' or, when implemented, to use the numerical integration.
3) in commit e0834fa I also showed a BUG in pointsAt(t=T,normalized=True) which returned points at a WRONG relative length. Please run the attached example to check the BUG.

(file #32331)

a draft of splitAtLength(L) has been committed.

Dear pyFormex developers,

I just updated pyformex to version 1.0.0-a6.

I needed to split a curve C in 4 parts at relative curvilinear positions (20%, 50%, 70%).

It seems that the way now is:

T=array( [0.20,0.50,0.70] ) # relative curvilinear positions
CP = C.approx(nseg=100) # convert curve to polyline
Cparts = CP.splitAt(t=CP.atLength(T)) # list of 4 polylines

This is a basic functionality but to use it I needed to convert my distances into a parameter t (what it is that?) and use t to split the polyline.

A user would be more familiar with the 'position' or 'relative position' or 'distance from the start' rather than the parameter t.

Maybe this functionality could become a friendly general method for all curves like

def splitAtDistance(curve, distance, relative=True)
   ...
   return listOFpolylines

This would split a curve at N absolute (0 to total length) or relative (0 to 1) positions at specified distances from the start and return N+1 polylines.

What do you think?
Gianluca