xentselx + vlax-curve-getclosestpointto

Okay, the WCS2OCS thing is hopefully working, BUT:

I still have this annoying problem with the fact that the (xentselx) functions
return the pick point without any meaningful Z value. I've complained about
this before. Suppose you want to pick a segment of a 3DPolyline (nested or
not). An (osnap pt "_quick,_near") might find a point on another nearby object.
A (vlax-curve-getclosestpointto) might find a different segment because the
distance is affected by the Z values.

Example:
Command: (command "_.3dpoly")(mapcar 'command '((0 0 100)(10 10 110)(20 20 120)
""))
_.3dpoly
Specify start point of polyline:
Specify endpoint of line or [Undo]:
Specify endpoint of line or [Undo]:
Specify endpoint of line or [Close/Undo]:
Command: (nil nil nil nil)

Command: (setq pick (nentselp '(14.99 15.01)))
(<Entity name: 400b7de8> (14.99 15.01 0.0))

Command: (setq object (vlax-ename->vla-object (entlast)))
#<VLA-OBJECT IAcad3DPolyline 025f6904>

Command: (vlax-curve-getclosestpointto object (cadr pick))
(0.0 0.0 100.0)

Anyone care to propose a solution to getting the correct point?

 

Perhaps using the appropriate tool for the job
might work:

vlax-curve-GetClosestPointToProjection

 

Hey John, here's a thought - have you tried using
vlax-curve-GetClosestPointToProjection?

jb

 

Thank you kindly, Tony/James. Why did I never see that one before!? Now I'm a
little daunted by what 'Normal to use when the object is nested... the nested
object's normal? it's parent's normal? or just plain '(0 0 1)?

 

John,
If you are worried about what point the pick point appears close to then I
would imagine you would need the normal of the DCS.

(trans '(0 0 1) 2 0)

 

Thanks, Doug. I expect a little experimentation is in order. But with the
usual collection of brains contributing, we may be able to nail it down. Tony
is probably the most capable of unraveling the mysteries, but I wish Jon Fleming
would participate a little more. I sorta think of him as the transformation
meister. Then again, it was Larry Leuallen who unraveled the inverse matrix
method.

Just an aside, but are the regulars maybe getting bored of this scene?

 

Hi John,

Just pretty busy. I try to participate when its of interest and
I don't think its going to take hours. A lot of the questions
lately haven't been all that interesting. There have been a
lot of folks looking for handouts without much real learning
happening.

I am curious why the trans function hasn't come up in a
few of these threads or why the getucsmatrix and transformby
methods haven't been discussed. Transforming points is one
thing but drawing entities normal to another ucs seems to
require different strategies IMO. Course I could be getting
past it.

Seemed like the discussions a year ago were much more
alive with people learning the new methods.

Thanks for keeping the level of the discussion up! I imagine
there are still lurkers out there who are benefitting.

About inverse matricies, I'm afraid the concepts probably
did not originate with Larry or Jon, although they may have posted
the earliest AutoLISP ones. I didn't check the newsgroups till 2 years ago.
I remember reading about 3d transformation using matricies
when I was in college(long before AutoCAD). I had to
program my own CAD system circa 1980 on a Textronix terminal
using the campus IBM 360 and the APL language to draw my thesis
project. APL is marvelous for that stuff. I was able to design
and draw an amphitheater for 5000 and show and plot the drawings
in isometric section and plan.

Regards,
Doug

 

Wow! Now my dreams tonight will be 4-dimensional! ((Z Z Z Z)(Z Z Z etc.))