Problems with IntersectWith

[Lee Mac]

I am trying to determine the maximum and minimum points on a curve by using a combination of the BoudingBox method and the IntersectWith method, however I am consistently receiving nil results, and I cannot work out why.

Below is my code - I have even added a "fuzz factor" to make sure that the objects intersect - but still with no luck:

(defun getExt  (cObj / fuzz doc spc cObj Minp Maxp tmp1 tmp2 Maxpt Minpt)
  (vl-load-com)

  (setq fuzz 0.001)

  (setq doc (vla-get-ActiveDocument (vlax-get-Acad-Object))
        spc (if (zerop (vla-get-activespace doc))
              (if (= (vla-get-mspace doc) :vlax-true)
                (vla-get-modelspace doc)
                (vla-get-paperspace doc))
              (vla-get-modelspace doc)))

  (or (eq 'VLA-OBJECT (type cObj))
      (setq cObj (vlax-ename->vla-object cObj)))

  (vla-getBoundingBox cObj 'Minp 'Maxp)
  (setq Minp (vlax-safearray->list Minp)
        Maxp (vlax-safearray->list Maxp))

  (setq Maxpt (car
                (vlax-list->3D-point
                  (vlax-invoke
                    (setq tmp1
                      (vla-addline spc
                        (vlax-3D-point
                          (list (car Minp) (- (cadr Maxp) fuzz) 0.0))
                            (vlax-3D-point Maxp)))
                              'IntersectWith cObj
                                 acExtendNone))))

  (setq Minpt (car
                (vlax-list->3D-point
                  (vlax-invoke
                    (setq tmp2
                      (vla-addline spc
                        (vlax-3D-point
                          (list (car Maxp) (+ (cadr Minp) fuzz) 0.0))
                            (vlax-3D-point Minp)))
                              'IntersectWith cObj
                                acExtendNone))))

  (list Minpt Maxpt))

(defun vlax-list->3D-point  (lst)
  (if lst
    (cons (list (car lst) (cadr lst) (caddr lst))
          (vlax-list->3D-point (cdddr lst)))))

(defun c:test ()
  (getExt (car (entsel))))

[kpblc2000]

Try to check this code:

(defun get-exts (obj fuzz / minp maxp)
  (if (not fuzz)
    (setq fuzz 1e-3)
    ) ;_ end of if
  (if (setq obj (cond
                  ((= (type obj) 'ename) (vlax-ename->vla-object obj))
                  ((= (type obj) 'vla-object) obj)
                  ) ;_ end of cond
            ) ;_ end of setq
    (progn
      (vla-getboundingbox obj 'minp 'maxp)
      (setq minp (vlax-safearray->list minp)
            maxp (vlax-safearray->list maxp)
            ) ;_ end of setq
      (list (mapcar (function (lambda (x) (- x fuzz))) minp)
            (mapcar (function (lambda (x) (+ x fuzz))) maxp)
            ) ;_ end of list
      ) ;_ end of progn
    ) ;_ end of if
  ) ;_ end of defun

[Lee Mac]

Thanks for your code kpblc2000, that better adds the fuzz factor to the measurements of the bounding box, but its the intersectWith part that is causing me grief.

I cannot get it to register an intersection at all - when clearly there is.

[Lee Mac]

Finally sorted the problem - thanks to Sean Tessier from over at the Swamp -

Turns out that the GetBoundingBox method adds a small Z component to the resulting points, which needed to be ignored.

Thanks for helping with the fuzz factor adjustment, here is the final code:

(defun getExt  (cObj / fuzz doc spc cObj Minp Maxp tmp1 tmp2 Maxpt Minpt)
  (vl-load-com)

  (setq fuzz 0.00001)

  (setq doc (vla-get-ActiveDocument (vlax-get-Acad-Object))
        spc (if (zerop (vla-get-activespace doc))
              (if (= (vla-get-mspace doc) :vlax-true)
                (vla-get-modelspace doc)
                (vla-get-paperspace doc))
              (vla-get-modelspace doc)))

  (or (eq 'VLA-OBJECT (type cObj))
      (setq cObj (vlax-ename->vla-object cObj)))

  (vla-getBoundingBox cObj 'Minp 'Maxp)
  (setq Minp (mapcar
               (function
                 (lambda (x) (+ x fuzz))) (vlax-safearray->list Minp))
        Maxp (mapcar
               (function
                 (lambda (x) (- x fuzz))) (vlax-safearray->list Maxp)))

  (setq Maxpt (car
                (vlax-list->3D-point
                  (vlax-invoke
                    (setq tmp1
                      (vla-addline spc
                        (vlax-3D-point
                          (list (car Minp) (cadr Maxp) 0.0))
                            (vlax-3D-point
                              (list (car Maxp) (cadr Maxp) 0.0))))
                              'IntersectWith cObj
                                 acExtendNone))))

  (setq Minpt (car
                (vlax-list->3D-point
                  (vlax-invoke
                    (setq tmp2
                      (vla-addline spc
                        (vlax-3D-point
                          (list (car Maxp) (cadr Minp) 0.0))
                            (vlax-3D-point
                              (list (car Minp) (cadr Minp) 0.0))))
                              'IntersectWith cObj
                                acExtendNone))))

  (list Minpt Maxpt))

(defun vlax-list->3D-point  (lst)
  (if lst
    (cons (list (car lst) (cadr lst) (caddr lst))
          (vlax-list->3D-point (cdddr lst)))))


(defun c:test ()
  (setvar "PDMODE" 3)
  (foreach pt (getExt (car (entsel)))
    (command "_point" "_non" pt))
  (princ))