Help, need to create a boundary around a mass of scattered points...

[coburnj]

CIVIL3D 2012

I'm trying to create a boundary (either 2D or 3D polyline) around a group of random scattered cogo points.

The boundary or polyline vertices needs to be "attached" to, or at least sharing the same x,y,z coordinates as the points that create the perimeter of the group of scattered points.

The reason for this is to eliminate the lengthly tedeous process of creating a polyline and having to snap each consecutive vertice to the next point on the perimeter of a mass group of points (like 1000's of points).

I have looked into using the "Shrinkwrap" command, but it's not doing what I need.  It only seems to duplicate an existing polyline that surrounds the group of points, failing to attached to the points on the perimeter.

Please see attached pictures...

Thanks for any help that can be provided...

John

[Alfred.NESWADBA]

Hi,

if you create a suface based on these points, set the style to show the border, then extract the border of the surface ==> will result in a polyline (would be a 2min way).

If that's what you look for, ok; if not ... what is the rule to make it better? With "rule" I mean what would be your strategy to get a (for you) better result?

- alfred -

[coburnj]

Alfred, thanks for your prompt reply!

Basically that's exactly what I would like, without having to create the surface.  Possibly a .lsp routine or something to that effect...

Regards,

John

[mikesmi]

Out of curiosity why don't you want to create a surface?  Is it extremely large?

[coburnj]

I'm looking for the most efficient route possible.  I realize that creating a surface, extracting the boundary and then editing it to fit to my preference is significantly more efficient than tracing the outline perimeter of a mass group of points.  But, I'm reallly just looking to invoke a command that will allow me to select a group of points and have a perimeter boundary created.

[neilyj666]

If you are determined not to use the surface method then the easiest manual method is probably to set OSMODE to Node and OSNAPOVERRIDE to 1, this will only let you select the nodes but it could be a bit tedious.

Another way of approaching the surface method is to create the surface and then add a destructive boundary to delete spurious triangles.

[mathewkol]

Basically there is no built in wlmethod to do what you need. So either you pay someone to create a tool for you (or someone here offers one for free) or you go to the next most efficient method...surface creation. Delete the surface after. Creating that surface is seconds worth of work.

[coburnj]

its the editing of the boundary that i'm trying to avoid...the surface boundary works, but there is still plenty editing to do...I agree, it's better than the long manual way...but I need more efficiency...

Thanks to all who have responded, it's much appreciated...

Regards,

John

[TerryDotson]

If you were to consider third party software, we've just added Shrinkwrap Points to the MapWorks Points module.  Simply select the Civil3D points and it instantly generates a 3dPoly.

[mikesmi]

Do you use the surface "delete line" command in conjuction with the CP (crossing poly window)  makes for very easy boundary editing.  See example pic where I are editing the boudary in one shot.  No selecting points just removing lines

procedure:

select surface

select edit surface

select delete line

type cp at the command line press enter

create funky shape around surface

enter to delete all lines touched

[Alfred.NESWADBA]

Hi,

>> but there is still plenty editing to do

And that's why I mentioned  "what is the rule to make it better?"  It's an awesome job to get the rules defined, because you will always find situations where the border should use another connection as it did. 

And to prove this theory look at this picture, is the blue or the red version the "correct border" (both based on the same point-locations)? I don't know it, how should a software check whats better and what not?

     

What I know: the version of Civil (with the option of max. triangle-edge-length) is quite good!

- alfred -

[coburnj]

I'm not too sure what you mean by "rules"...

What I'd like to see:

initiate a command;

prompt to "pick a point" within the group (typically the user would click their curser or cross-hair in the middle of the grouping);

the routine then starts a polyline on the point furthest away from the "pick-point";

the next part of the routine would create a second vertice of the polyline on the next closest point to that vertice that is furthest away from the first "pick point";

continuing around the perimeter and finishing on the first vertice and closing the polyline...

...something to that effect...

[Alfred.NESWADBA]

Hi,

>> I'm not too sure what you mean by "rules"

I meant a list of definitions for different situations that makes it possible for a developer to find through all situations to build the outline. And imho it's not possible to create definitions that work in every case (bad for a developer to have no regulation to follow).

>> What I'd like to see: initiate a command; [...]

I must admit that my english is not good enough to follow your description in detail (especially I don't understand the part with the second point, most far away from the start-point).

I showed two examples above, lets start at the lower left point. What would help me (or any other interested in algorythms) would be:

• imagine you have a textlist (no graphical display) with x/y coordinates
• search the point with minimum-x/minimum-y to get the start-point
• ....and what are now your thoughts to find the next point that builds up the border (and does this concept work for any situation, for all next following points)

- alfred -

[coburnj]

By no means am I a programmer, and with that being said I need to visualize the routine graphically...I don't know how to respond...

I really do appreciate your efforts tho...

[coburnj]

From Carlson Software:

"Shrinkwrap: introducing a Carlson feature, which creates a closed polyline, that encloses a given set of entities to be used in various other routines for inclusion or exclusion of entities."

if anyone has used this new feature, this is what I need in Civil3D 2012...

[mathewkol]

Civil 3D has a shrinkwrap tool. It doesn't work with points. Does the Carlson tool?

I'm pretty sure we all know what you want. Point is, there is no tool for it in C3D. Terry offered his tool. Buy it if the surface suggestions do not suit your needs. (Assuming Terry's tool does).

[TerryDotson]

Civil 3D has a shrinkwrap tool.  It doesn't work with points.  Does the Carlson tool?

The question for Carlson would be "does it work inside Civil3D with AECC_POINTS?"

Terry offered his tool.  Buy it if the surface suggestions do not suit your needs.  (Assuming Terry's tool does).

The routine worked fine on an approximation of the OP's capture, example attached.  It's based on a simple minimum turned angle logic.  If needed we could automate a triangulation (with maximum edge parameter) and extract the border.  What we don't believe in is jumping through hoops to get the results you need.

To the OP (original poster), request a full working 21-day eval and find out for yourselves.  I can be reached at dotson [at] dotsoft [dot] com.

[coburnj]

Thanks guys, for all your help.

Regards,

OP

[rkmcswain]

@TerryDotson - yeah, I know it's 12.5 years later, but is this shrinkwrap tool still available? I couldn't find it (searching for "Shrinkwrap" on this page: https://www.dotsoft.com/mapworks.htm )

[TerryDotson]

@rkmcswain Yes, it's on the menu / ribbon as Points > Draw > Shrinkwrap.  I know of three approaches to it, so I'll look into adding the other methods (and to the web page).