(vlax-curve-getParamAtPoint ename point)
The vlax-curve-getParamAtPoint function calculates the value of the parameter at a specified point on the specified entity.
ename specifies the entity to be evaluated.
point specifies a point on the entity provided as a list of three floating-point numbers representing the WCS coordinates of that point.
The function returns the value of the parameter as floating-point number. If the function fails, it returns nil.
Examples
Assuming that en points to an ellipse and pt is point on that ellipse:
: (setq en (entlast))
<EName: 045d4b64>
: (setq pt (getpoint))
(32.714 30.650 0.000)
: (vlax-curve-getParamAtPoint en pt)
14.58296