how to convert 2d polyline to polyline

Can you post a .dwg?

most importantly, i think we can all agree that splines suck.

That does seem to be the prevailing opinion, though I’m not sure why.

Splines are too unpredictable to my liking. They never go where you're Pline was placed (Point for point) where as Fillet does a good job in both rounding off and not screwing you over!

Angry rant over.

I’m reading between the lines of your post; Pardon me if I’ve misinterpreted.

If the unmodified data is in the form of a straight segment Polyline then a PEDIT – SPLINE does morph as you said. The curve no longer passes through the original vertices. It sounds like you prefer PEDIT – FIT, as it maintains a connection to the original vertex information. The path, however, can meander quite drastically from one vertex to the next.

There are better interpolation schemes for vertex data. Splines utilize that scheme, but a CAD operator has to use the SPLINE command; specifically the FitPoint variant. Now the resultant curve will pass through the vertex. The scheme is further refined by the various Knot Parameterization options.

See the attached example.

The SPLINE command requires more work, but the enhanced interpolation may be worth the effort.

VertInterp.dwg

Splines are used where splines are needed.

Polylines are used where polylines are needed.

Splines are used where splines are needed.

Polylines are used where polylines are needed.

Yes indeed!!

Splines are used where splines are needed.

Polylines are used where polylines are needed.

That statement seems a bit incomplete. A student may find that it creates more questions than it answers.

What are some of the determining factors that encourage the use of one entity over the other? If we were to consider intermittent elevation data (as may be pertinent to the resurrector of this thread, given the discipline designation as CIVIL), what would be the most accurate form of contour? Or, more mechanical, a limited budget needs wing cross sections CNC cut based on NACA airfoil data?

That statement seems a bit incomplete. A student may find that it creates more questions than it answers.

...and it should. I just didn't want to leave the previous statement that seemed to indicate there is something wrong with using splines.

Splines are absolutely necessary where splines are required. I use them all the time (but I use a different Autodesk CAD program most of the time and it doesn't even have polylines).

Hmmm, what entity type is a Helix in AutoCAD, well List indicates Helix - but it is a spline curve.

...and it should. . . . .

Ah! I see, then, that we are making similar recommendations, i.e., investigate whether Spline have anything to offer a particular workflow. I think that shift in attitude would benefit many that are more familiar with the “AVOID SPLINES AT ALL COST” mentality.

. . . . a different Autodesk CAD program most of the time and it doesn't even have polylines . . . .

That interesting. It’s apparent that Autodesk had devoted additional resources to spline geometry. Based on AutoCAD, though, I wasn’t sure if they were fully committed due to a couple of bugs (rather obscure, fortunately) that had not received attentionin the latest release. It’s nice to see that they take the process seriously.

select all 2dpolyline -> explode -> select all line-> join = polyline

select all 2dpolyline -> explode -> select all line-> join = polyline

In my opinion it is too complicated algorithm. Personally, I use TotalPurge utility. It automatically converts any 2DPOLYLINE into LWPOLYLINE.

It will convert 2d polylines to polylines

In my opinion it is too complicated algorithm. Personally, I use TotalPurge utility. It automatically converts any 2DPOLYLINE into LWPOLYLINE.

Thanks to y'all! I had the same issue of converting 2Dpolyline to Polyline. Now I know I have 4 options: Explode -> select all -> join; Convertpoly; Overkill; and TotalPurge.

Somehow, only Overkill works for me. I'm thankful for everybody who contributed to this thread.