Topic: Question about selecting an object from a point

[Kerry]

Have a play with something like this

Code: [Select]

[color=green];; bd1.lsp[/color]
(defun [color=blue]c:bd1[/color] (/ Limit Pre Pt1 Sel Xpt1 Ypt1)
  (vl-load-com)
  [color=green];; sample by kdub@theSwamp
  ;; Select an object at or in in a relative position to the selected Point.
  ;; If the Object is not found, change the point negative X vector 0.01
  ;; untill the search limit is reached
  ;; Will only select object if the point is ON screen.[/color]
  (setq pt1   (getpoint [color=Maroon]"\nPoint to Test:"[/color])
        pre   0.01
        xpt1  (car pt1)
        ypt1  (cadr pt1)
        limit (- xpt1 15)
  )
  (vl-cmdf [color=Maroon]"zoom"[/color] [color=Maroon]"E"[/color])
  (while (and (> xpt1 limit)
              (not (setq SEL (nentselp [color=Maroon]""[/color] (list xpt1 ypt1))))
         )
    (setq xpt1 (- xpt1 pre))
  )
  (vl-cmdf [color=Maroon]"zoom"[/color] [color=Maroon]"P"[/color])
  SEL
)


[Brick_top]

thanks a lot for your code

Unfortunately I've not been able to understand if it is working or not

It prompts me to an entity name and a coordinate of the point I picked right?

[Brick_top]

if I remove the vl-cmdf parts it gives me the coordinate of the object I want to select

[Kerry]

Retutns the value of SEL

If it works :
returns the entity and pickpoint from nentselp

if it fails :
returns nil

//-----------------------
The entity MAY NOT be at the point selected.

Please note  the selection functions return the point selected but select onjects inside the pickbox.

The example shown is using a circle with a 10.0 radius ... the selected point was (-9.87 0.0 0.0) and the circle circumference was just in the pickbox.

There are several ways to determine the actual entity point  ... but will not be required if you only want the entity.

[Kerry]

if I remove the vl-cmdf parts it gives me the coordinate of the object I want to select

NO !

removing the Zoom commands will just stop the point being selected if it's off screen.

[Brick_top]

I removed the declared variable sel to test from the command line what entity it was but it isn't the one I want

But if I remove the vl-cmdf parts it selects the entity I expect it to select, it if is on screen

[Kerry]

I removed the declared variable sel to test from the command line what entity it was but it isn't the one I want

But if I remove the vl-cmdf parts it selects the entity I expect it to select, it if is on screen

Everything will work just as you expect it to, unless your expectations are incorrect. 

[Kerry]

But if I remove the vl-cmdf parts it selects the entity I expect it to select, it if is on screen

I will select the correct entity with the zoom commands left in ..

I removed the declared variable sel to test from the command line what entity it was but it isn't the one I want

Care to explain this in more detail. ?
Is the entity within the 'limit' distance as nominated in the code ?
(if a limit is not expressed, the code will continue untill it runs out of memory or finds something 5 kilometers away)

[Brick_top]

I guess I have found out what I was doing wrong

I was testing without a closed object, when I try your routine with a closed polyline it works

[Kerry]

I guess I have found out what I was doing wrong

I was testing without a closed object, when I try your routine with a closed polyline it works

NO!

a closed object is NOT required.


Please don't make assumptions based on limited and possibly faulty testing ... you'll remain sane longer

[Brick_top]

but when I don't use a closed object it "doesn't select the next object in the -x direction" In case this was what it was expected to do

I'm sorry for all the trouble

[Kerry]

but when I don't use a closed object it doesn't select the next object in the -x direction

I'm sorry for all the trouble

Can you post a drawing of the data you've using, and a description of what you expect.

What do you mean NEXT object ... there was never discussion of a NEXT object 

[Brick_top]

I'm sorry for not being clear enough

I was trying to select the next object in the -x direction from picked point

[Brick_top]

Here is the drawing

[Brick_top]

there might be a precision error, because if I test this in a drawing with a smaller zoom extents area it works as I was expecting, which was for it to select the "next" object in the -x direction from the picked point