Author Topic: Minimum distance between two vlax-curve objects  (Read 22142 times)

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Joe Burke

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Minimum distance between two vlax-curve objects
« on: May 20, 2008, 12:16:36 PM »
Think about this.

Group: autodesk.autocad.customization Tony Tanzillo <tony.tanzi...@worldnet.att.net> wrote in article <3664CFB1.
93B45...@worldnet.att.net>... Bob - This isn't remotely close to what he needs.
AutoCAD can't find the minimum clearance between two objects as Microstation can.

I think Tony is wrong about this. I wrote an alorithm which works in most cases for any two curve objects. The function is about eight lines of code. Can you guess how it works?


ronjonp

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Re: Minimum distance between two vlax-curve objects
« Reply #1 on: May 20, 2008, 03:38:48 PM »
The only way I can think of doing it is by stepping points on one object and using vlax-curve-getclosestpointto to the other object. Then store the two points and distance in a list then sort the list by shortest distance :?

How'd you do it Joe?

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VovKa

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Re: Minimum distance between two vlax-curve objects
« Reply #2 on: May 20, 2008, 04:18:11 PM »
to use vlax-curve-getclosestpointto on arcs one will have to build an approximation and that is not 100% accurate

Kerry

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Re: Minimum distance between two vlax-curve objects
« Reply #3 on: May 20, 2008, 06:34:57 PM »
Think about this.

Group: autodesk.autocad.customization Tony Tanzillo <tony.tanzi...@worldnet.att.net> wrote in article <3664CFB1.
93B45...@worldnet.att.net>... Bob - This isn't remotely close to what he needs.
AutoCAD can't find the minimum clearance between two objects as Microstation can.

I think Tony is wrong about this. I wrote an alorithm which works in most cases for any two curve objects. The function is about eight lines of code. Can you guess how it works?



Joe, I haven't seen the thread, but was the reference to the OutOfTheBox application. ?
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Joe Burke

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Re: Minimum distance between two vlax-curve objects
« Reply #4 on: May 20, 2008, 10:12:08 PM »
Kerry,

I don't have time for a full reply now.

I'll just say I think Tony meant vanilla AutoCAD. Does some vertical app have a minimum distance tool?

More later...

daron

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Re: Minimum distance between two vlax-curve objects
« Reply #5 on: May 21, 2008, 09:34:13 AM »
Quote
...minimum clearance...
ADT can for stair openings, so why wouldn't other apps be able to?

Joe Burke

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Re: Minimum distance between two vlax-curve objects
« Reply #6 on: May 21, 2008, 09:54:08 AM »
I thought I posted this, but later I don't see it.

Here's some beta code which demonstrates the idea. It should work in the vast majority of typical cases. I'm aware there are a few odd cases where it will not. I'm working on those. See inline comments.

Comments and suggestions welcome.

Joe Burke

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Re: Minimum distance between two vlax-curve objects
« Reply #7 on: May 21, 2008, 10:26:59 AM »
to use vlax-curve-getclosestpointto on arcs one will have to build an approximation and that is not 100% accurate

Given there's no such thing as 100% accurate within AutoCAD, try the code I posted.

It uses an approximation method for all supported object types because one sub-routine can process all object types. IOW, a lot less code than would be needed if the line to line condition used a specific sub-routine. Which is possible.

Joe Burke

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Re: Minimum distance between two vlax-curve objects
« Reply #8 on: May 21, 2008, 10:36:47 AM »
The only way I can think of doing it is by stepping points on one object and using vlax-curve-getclosestpointto to the other object. Then store the two points and distance in a list then sort the list by shortest distance :?

How'd you do it Joe?

Something like that, but without using vl-sort. See the MD:ObjObj sub-function in the code I posted.

ronjonp

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Re: Minimum distance between two vlax-curve objects
« Reply #9 on: May 21, 2008, 10:44:26 AM »
Here's my "ghetto-fied" solution... :-D

Code: [Select]
(defun rjp-getmindistof2curveobjs
       (div / inc len lst n obj1 obj2 pt1 pt2)
  (if (and (setq obj1 (car (entsel "\nSelect first curve object: ")))
   (setq obj2 (car (entsel "\nSelect second curve object: ")))
      )
    (progn
      (setq len (vlax-curve-getdistatparam
  obj1
  (vlax-curve-getendparam obj1)
)
    n 0.0
    inc (/ len div)
      )
      (repeat div
(setq pt1 (vlax-curve-getpointatdist obj1 n)
      pt2 (vlax-curve-getclosestpointto obj2 pt1)
      n   (+ inc n)
      lst (cons (list (distance pt1 pt2) pt1 pt2) lst)
)
      )
      (setq lst (vl-sort lst
(function (lambda (d1 d2)
     (< (car d1) (car d2))
   )
)
)
    lst (car lst)
      )
      (grdraw (cadr lst) (caddr lst) 1)
      lst
    )
  )
)
(rjp-getmindistof2curveobjs 1000)

*removed line creation and added vector
« Last Edit: May 21, 2008, 11:35:59 AM by ronjonp »

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CAB

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Re: Minimum distance between two vlax-curve objects
« Reply #10 on: May 21, 2008, 11:06:49 AM »
Here is my first try. :-)
« Last Edit: May 21, 2008, 11:11:41 AM by CAB »
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Joe Burke

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Re: Minimum distance between two vlax-curve objects
« Reply #11 on: May 21, 2008, 11:37:16 AM »
Here is my first try. :-)

Hi Alan,

I haven't tried your code, but it looks right.

As I said to ronjonp, there's really no reason to make a list of distances and then use the min or the vl-sort function.

And I think setting step to (/ len 1000) is total overkill. You don't need that many iterations if your code works like mine.

Regards
Joe

ronjonp

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Re: Minimum distance between two vlax-curve objects
« Reply #12 on: May 21, 2008, 11:42:00 AM »
Here is my first try. :-)



And I think setting step to (/ len 1000) is total overkill...

Regards
Joe

Depends on the length of the items tested...if the lines are 10000 ft long then the check is only every 10 feet  :-P

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Joe Burke

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Re: Minimum distance between two vlax-curve objects
« Reply #13 on: May 21, 2008, 11:55:57 AM »
Here is my first try. :-)



And I think setting step to (/ len 1000) is total overkill...

Regards
Joe

Depends on the length of the items tested...if the lines are 10000 ft long then the check is only every 10 feet  :-P

Not correct. The length of the objects involved is not an issue. Study my code.

VovKa

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Re: Minimum distance between two vlax-curve objects
« Reply #14 on: May 21, 2008, 12:01:27 PM »
to use vlax-curve-getclosestpointto on arcs one will have to build an approximation and that is not 100% accurate

Given there's no such thing as 100% accurate within AutoCAD, try the code I posted.

my reply concerned Ron's suggestiong, but your tricky approach is a wow :)