vla-intersectWith

[Moshe-A]

hi guys,

it looks like (vla-intersectWith) funcrion does not work well

i have attached a small test i made (test.lsp + test.dwg)

when a request is made for an intersection between obj1 and obj2, instead it returns one endpoint of obj2

the same is for obj3 and obj2 ... it returns the other endpoint of obj2

how can i fix this?

thanks in advance

Moshe

[ВeekeeCZ]

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@Moshe-A wrote:

hi guys,

it looks like (vla-intersectWith) funcrion does not work well

i have attached a small test i made (test.lsp + test.dwg)

when a request is made for an intersection between obj1 and obj2, instead it returns one endpoint of obj2

the same is for obj3 and obj2 ... it returns the other endpoint of obj2

how can i fix this?

thanks in advance

Moshe

---

There is nothing to fix. Your test routine is working fine and the result is correct (ACAD 2015). See the screenshot.

Maybe try to close both Autocad and Vlide and run it again. 

[hgasty1001]

Hi,

I'm not sure but looks like an OSNAP problem, try setting "OSMODE" variable to 0 before the intersect calculation.

Gaston Nunez

[Moshe-A]

Hi Guys,

Sorry my respond is late, don't know why but i stopped getting an email when you replied. 

After playing alot with (vla-intersectWith) i came out with this conclusion:

if the two lines are apart but one extends beyond the intersection point, the option 'acExtendBoth' is not suitable

(better autodesk may fix this to return the intersection point or atleast nil or error) instead 'acExtendthisEntity' or 'acExtendOtherExntity' should be used.

the only time 'acExtendBoth' will work is when the two objects does not cross the intersection point (both objects need to be extend)

so i developed this function:

(defun get_intersection_point (obj0 obj1 / option)
   (vl-some
    '(lambda (option)
      (vla-intersectwith obj0 obj1 option)
     )
     (list acExtendNone acExtendThisEntity acExtendOtherEntity acExtendBoth)
   )
)

Happy New Year to all   

Moshe

[dbroad]

Moshe,

Vla-intersectwith seems to work correctly with your test.dwg.  The results are consistent with the help file descriptions when using any of the options acextendboth, acextendthisentity, acextendotherentity, or acextendnone with any pair of lines.  You should avoid using vlax-safearray->list, however, unless you are certain that an intersection exists.  If not certain, then you should use (safearray-value(variant-value(vla-intersectwith a b <whateverextendoption>))).  It will return nil if an intersection does not exist whereas vlax-safearray->list will return an error unless the intersection exists.  For the most probability of an intersection, the acextendboth should be used but it depends on the program goals.

[Moshe-A]

dboard,

didn't knew of (safearray-value) and it doesn't appear in help file. neither (variant-value) but seen it here long time ago.

thank you very much for your help

Moshe

[dbroad]

You're welcome.  Since you usually have to use both functions together, I usually define this function:

(defun safelist (v) (safearray-value (variant-value v)))

[hmsilva · Accepted solution]

Hi Moshe,
in addition to dboard's great advices, what I usually use to skip safearray and variant conversion functions, is:

(setq A (vlax-invoke obj1 'IntersectWith obj2 acExtendBoth))

will return a REAL numbers list or nil if no intersection found.

Hope this helps,
Henrique

[dbroad]

Thanks @hmsilva .  I thought I had tried the shorter vlax-invoke  approach before I posted but I must have used vlax-invoke-method instead.  Thanks for the additional info.

[Moshe-A]

Henrique,

wow, thanks for this tip 

Moshe

[hmsilva]

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@Anonymous wrote:

Thanks @hmsilva .  I thought I had tried the shorter vlax-invoke  approach before I posted but I must have used vlax-invoke-method instead.  Thanks for the additional info.

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@dbroad

You're welcome, dbroad!

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@Moshe-A wrote:

Henrique,

wow, thanks for this tip 

Moshe

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You're welcome, Moshe
Glad I could help! 🙂

Henrique

[ВeekeeCZ]

You can also use Lee Mac's sub here which uses the same approach as Henrique mentioned. In addition it makes a list of all possible points.