Find specfic elevation on Featureline

[AllenJessup]

I thought I'd find this through a search. But I haven't turned up anything yet.

I have a Featureline going up a slope and want to hold a certain slope and find where on the Featureline a specific elevation falls. I can calculate it from the final elevation or draw a polyline at the specific elevation, interposed on the Featureline, and use it to trim the Featureline. But I'm always looking for better ways of doing things.

So does anyone know of a better way to find where elevation 440.0 falls on a featureline?

[Ranjit_Singh]

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@AllenJessup wrote:

I thought I'd find this through a search. But I haven't turned up anything yet.

I have a Featureline going up a slope and want to hold a certain slope and find where on the Featureline a specific elevation falls. I can calculate it from the final elevation or draw a polyline at the specific elevation, interposed on the Featureline, and use it to trim the Featureline. But I'm always looking for better ways of doing things.

So does anyone know of a better way to find where elevation 440.0 falls on a featureline?

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I do exactly that but instead of trimming, I start a new line and use the intersect osnap to see where that elevation is.

I would also like to know if there is a better way.

[AllenJessup]

I just added another way. Set the units to 8 decimal places and draw a line using the Nearest Osnap. Run the Osnap along the Featureline and watch the elevation. I can usually hit the elevation with zeros out to 5 decimal places.

[AllenJessup]

Nice one Joe! Thanks.

[TerryDotson]

If you were to consider third party add-ons, C3D FeatureTools contains a mark tool that will mark a specified elevation on all segments of a selection set of featurelines (or 3dPolys, etc) in a singe, quick operation (no jumping through hoops).  This tool places a point object, a companion break tool does the same if you want to chop them up.

[AllenJessup]

Looks nice Terry. We're just not buying anything right now.

Thanks.

[Joe-Bouza]

No solution  ... comon I trying to topple Tim 

[AllenJessup]

I was getting to it. Figured I'd give others a chance to top you.

[Joe-Bouza]

[Ranjit_Singh · Accepted solution]

Here is just one more way using lisp

Spoiler

;created by Ranjit Singh, 11/29/2016
;marks elevation points on feature lines
(vl-load-com)
(defun c:setelpt  (/ vlaObj pts el pt modelspace adoc)
    (defun *error*  (errmsg)
        (if (not (wcmatch errmsg "Function cancelled,quit / exit abort,console break,end"))
            (princ (strcat "\nError: " errmsg)))
        (vla-endundomark adoc)
        (princ))
    (vla-startundomark (setq adoc (vla-get-activedocument (vlax-get-acad-object))))
    (setq vlaObj     (vlax-ename->vla-object (car (entsel)))
          pts        (vl-remove-if '(lambda (x) (atom x)) (test (vlax-invoke vlaObj 'GetPoints)))
          modelspace (vla-get-modelspace adoc))
    (initget 1)
    (setq el (getreal "\nElevation to be identified :"))
    (while el
        (mapcar '(lambda (x y)
                     (if (setq pt (inters x
                                          y
                                          (append (reverse (cdr (reverse x))) (list el))
                                          (append (reverse (cdr (reverse y))) (list el))
                                          T))
                         (vla-AddPoint modelSpace (vlax-3d-point pt))))
                pts
                (cdr pts))
        (initget 1)
        (setq el (getreal "\nElevation to be identified :")))
    (*error* "end"))

(defun test  (x)
    (cond ((null x) pts)
          (T (append (list (list (car x) (cadr x) (caddr x))) (test (member (cadddr x) x))))))

;

Spoiler

;

[AllenJessup]

Very nice. That will come in handy.

[MeowdyFren]

I know that this is an old post, but I am curious if you have used this lisp recently. When I try to run the lisp, I get an error "Hard error occurred *** internal stack limit reached (simulated)". I am running civil 3d 2018. Have you been able to run this lisp on this version? I would love to be able to use this with a project I am currently working on.

Thank You!

[AllenJessup]

It's working for me in 2020.2. Are you working at very high or negative elevations?