how to define direction in vla-offset

I have a basic line and I want to be able to run vla-offset based on a user
selection, but I can't think up the logic required to define what is
positive and what is negative. Anyone have insight on how to make a function
that would do this?

thanks,
kemp

 

Find the angle from the line to the pick point for the offset, if it's
between 180 degrees and 360 degrees it is negative. Note that this works
for lines and plines, but arcs are different. For an arc you need to
check the relationship form the point to the arc's radius point, if it'
smaller then the arc's radius then use a negative.

(defun cff-test ()
(setq offdist (getdist "\nOffset distance: ")
l1 (entsel "\nSelect line to offset: ")
l1 (car l1)
l1 (vlax-ename->vla-object l1)
)
(setq p1 (getpoint "\nSelect side to offset to: "))
(setq p2 (vlax-curve-getclosestpointto l1 p1 t))
(setq ang (angle p2 p1))
(if (< pi ang (* pi 2))
(setq offdist (- offdist))
)
(setq l2 (vla-offset l1 offdist))
)

HTH,
Jeff

 

I've been trying to figure out what this convoluted approach does for you.
It looks like it's asking the user to give the offset distance, and to
select the object to offset, and to pick which side to offset it to, so why
not just use the regular Offset command? Maybe I just don't understand the
intent of the original post.

Kent Cooper, AIA

 

I have my line defined as activeX data, and was hoping to find a simple
function to do this. Looks like the example given by Jeff Misler will work
but it is rather large.. I will try both this way and using the command
method and see which is faster. I assume a lot of you lisp pro's already
know the results I should get.

Thanks for the info,

kemp

 

The nice thing about using ActiveX is that there is no need to worry
about osnaps interfering with your results. Also, no unwanted data is
sent to the command line.

The example I posted was just that, and example. If i were to be using
that in a module that was creating the line to offset, or otherwise
working with a known line, and probably also have a known point, I would
use this little function.

It requires a valid line in vla-object format and a 2d/3d point to be
passed to it.

(defun off-test (ent point / p2 ang)
(setq p2 (vlax-curve-getclosestpointto ent point t))
(setq ang (angle p2 point))
(if (< pi ang (* pi 2)) t nil)
)

If this returns "T" then the offset is negative, nil is positive.

HTH,
Jeff