hi Gile , Lee ,
to judge a point in or at triangle ofcause can use area method , but it take a lot cal , I think the intersetion method is fastest .
hi Evgeniy , in the routine it can be
(defun ss-pitp (p l)
;;check point inside triangle .
;;by GSLS(SS)
(< ((lambda (a b c)
(+ (length (inters p a b c nil))
(length (inters p b a c nil))
(length (inters p c a b nil))
)
)
(car l)
(cadr l)
(caddr l)
)
9
)
)
however yours 'ins' is Excellent ! but the wholl routine is too slow if the points nums is more , e.g. 528 points in my often dwg .