Normal to ellipse from ext. Point ?

[SOFITO_SOFT]

Hi all:

¿ Someone knows how to solve the NORMAL TO ELLIPSE FROM A EXTERIOR (OUT) POINT in Alips and or Vlisp (2D) ?

Thanks in advance.

[Tharwat]

What do you mean from Normal to Ellipse ?

 

Is it from Circle to Ellipse ?

 

Tharwat

[GP_]

You mean the point on the ellipse closest to the external point?

 

(setq ELL (vlax-ename->vla-object (car (entsel "Select Ellipse"))))
(setq Pt_ext (getpoint "Exterior Point"))
(setq Pt_ell (vlax-curve-getClosestPointTo ELL Pt_ext))

[SOFITO_SOFT]

Tharwat Hello and greetings to everyone:

Is a very common Geometric construction in my work and that works out fine with AutoCAD object snap "PER". But I want to calculate either Autolisp from one point ( out to ellipse ) a line perpendicular ("normal" according to the usual geometric terminology) to an ellipse. Not find useful references on Google for this problem geometric.

Thanks for your interest.

[Lee Mac]

Something along these lines?

 

(defun c:test ( / e p ) (vl-load-com)
 ;; Example by Lee Mac 2010 - www.lee-mac.com

 (if
   (and (setq e (car (entsel)))
     (not
       (vl-catch-all-error-p
         (vl-catch-all-apply 'vlax-curve-getEndParam (list e))
       )
     )
     (setq p (getpoint "\nSpecify Point: "))
   )
   (entmakex
     (list
       (cons 0 "LINE")
       (cons 10 (trans p 1 0))
       (cons 11 (vlax-curve-getClosestPointto e (trans p 1 0)))
     )
   )
 )

 (princ)
)

[SOFITO_SOFT]

Sorry, I'm a rookie tender and finger walking fast.

[SOFITO_SOFT]

Hello everyone:

Lee Mac's solution is perfect (and fast ... on a Sunday!!!) to continue with my program. But it has been the question of how to solve the problem in the classical manner ... with lines, angles, perpendicular and compass .... Thanks you all... from Madrid (Spain-UE)

PD. In the drawing, for lovers of classical geometry : REED : SOLUTION TO SEARCH , GREEN : DATA, MAGENTA : AUXLIARS POSSIBLES LINES ?, BLUE : Known proportions.