(SETVAR "OSMODE" 8)
(setq a1 (getpoint "\n1.Nokta"))
(setq a2 (getpoint "\n2.Nokta"))
(setq a3 (getpoint "\n3.Nokta"))
(setq pm (command "_.3dpoly" a1 a2 a3 "C" ))

(SETVAR "OSMODE" 0)
(command "_.surfpatch" "CU" pm "" "")

(defun c:ww (/ pt)
  (if (setq pt (car (entsel)))
    (print (cadddr (assoc 10 (entget pt)))))
  (princ)
)

;;; Syntax:
;;; (pointxface P1 fent)
;;;
;;; Arguments:
;;; P1 - point on Z=0
;;; fent - entity 3dFace
;;;
;;; Retval:
;;; projection point on 3dface, if the projection of the point is outside the 3dface, the result will be nil

(defun pointxface (P1 fent / vertice1 vertice2 vertice3 V1 V2 V3 D1 D2 D aa bb somma zeta puntoinalto)
(setq vertice1 (cdr (assoc 10 (entget fent)))
       vertice2 (cdr (assoc 11 (entget fent)))
       vertice3 (cdr (assoc 12 (entget fent)))
       V1 (list (car vertice1)(cadr vertice1))
       V2 (list (car vertice2)(cadr vertice2))
       V3 (list (car vertice3)(cadr vertice3))
)
(setq D1 (- (* (- (car P1) (car V1)) (- (cadr V3) (cadr V1)))
     (* (- (cadr P1) (cadr V1)) (- (car V3) (car V1)))
  )
)

(setq D2 (- (* (- (car V1) (car P1)) (- (cadr V2) (cadr V1)))
     (* (- (cadr V1) (cadr P1)) (- (car V2) (car V1)))
  )
)

(setq D (- (* (- (car V2) (car V1)) (- (cadr V3) (cadr V1)))
    (* (- (cadr V2) (cadr V1)) (- (car V3) (car V1)))
)
)
(setq aa (/ D1 D))
(setq bb (/ D2 D))
(setq somma (+ aa bb))

(if (equal aa 0.00 0.000001)(setq aa 0.0))
(if (equal bb 0.00 0.000001)(setq bb 0.0))
(if (equal somma 1.0 0.000001)(setq somma 1.0))

(if (and (>= aa 0.0) (>=  bb 0.0)(<= somma 1.0)) ;;; Se aa>=0 and bb>=0 and aa+bb<=1 allora P è interno al triangolo o sul bordo. Altrimenti è esterno
  (progn
   (setq zeta      (/ (+ (-
    (- (* (- (car P1) (car vertice1))
  (- (* (- (cadr vertice2) (cadr vertice1))
(- (caddr vertice3) (caddr vertice1))
     )
     (* (- (cadr vertice3) (cadr vertice1))
(- (caddr vertice2) (caddr vertice1))
     )
  )
       )
       (* (- (cadr P1) (cadr vertice1))
  (- (* (- (car vertice2) (car vertice1))
(- (caddr vertice3) (caddr vertice1))
     )
     (* (- (car vertice3) (car vertice1))
(- (caddr vertice2) (caddr vertice1))
     )
  )
       )
    )
   )
   (* (caddr vertice1)
      (- (* (- (car vertice2) (car vertice1))
    (- (cadr vertice3) (cadr vertice1))
)
(* (- (car vertice3) (car vertice1))
    (- (cadr vertice2) (cadr vertice1))
)
      )
   )
)
(- (* (- (car vertice2) (car vertice1))
    (- (cadr vertice3) (cadr vertice1))
)
(* (- (car vertice3) (car vertice1))
    (- (cadr vertice2) (cadr vertice1))
)
      )
     )
puntoinalto (list (car P1) (cadr P1) zeta)
   )
  )
  (setq puntoinalto nil)
)

(princ "\n")
puntoinalto
)