topic Re: How to insert a curve into an alignment in Civil 3D Forum

How to insert a curve into an alignment

ebaker — Tue, 10 Mar 2020 21:14:11 GMT

I need to add a curve into an alignment. I'd like to do this similar to how you just hover over a midpoint grip on a pline and convert to arc, then just swing an arc. But it doesn't seem like it's that easy. I've tried a few of the curve options in the geometry editor, but when I get an arc in the right spot, then try to delete the straight segment I no longer need, it says it has to be part of the main entity.

Re: How to insert a curve into an alignment

Jowennl — Tue, 10 Mar 2020 21:31:58 GMT

Hi @ebaker ,

So many ways to do this. I’m on mobile so will send link for now as a guide.

check this out https://knowledge.autodesk.com/support/civil-3d/learn-explore/caas/CloudHelp/cloudhelp/2019/ENU/Civil3D-UserGuide/files/GUID-E70699B2-B709-463B-9627-06AF7048AC38-htm.html

https://knowledge.autodesk.com/support/civil-3d/learn-explore/caas/CloudHelp/cloudhelp/2019/ENU/Civil3D-UserGuide/files/GUID-7D245A7F-0D27-4051-B4E6-B465123CEF29-htm.html

Re: How to insert a curve into an alignment

Jowennl — Tue, 10 Mar 2020 22:26:57 GMT

Hi @ebaker

Here's a sample animated gif.

SampleAlignmentManipulation.gif

Another Sample.png

Cheers,

Jowenn

Re: How to insert a curve into an alignment

jae.kwon — Tue, 10 Mar 2020 23:42:37 GMT

Usually the best option is free curve fillet between two entities. What shape are you going for? If you like how plines behave, can't you just draw it with pline and use create Alignment from Object?

Re: How to insert a curve into an alignment

ebaker — Wed, 11 Mar 2020 01:48:26 GMT

Thanks for the reply,

I have a long alignment already created that is linked to a corridor with many regions. I needed to move a road and driveway intersection and using grips just isn't enough. I'd rather not redo the whole corridor, too. I just decurved two arcs in the original alignment in the area being modified, shifted the beginning and end of the S curve with no tangent between the curves. Basically, I have a 3 point line in a roughly 120 degree shape that I want two arcs on. Then just rebuild the corridor to the new alignment.

Re: How to insert a curve into an alignment

jae.kwon — Wed, 11 Mar 2020 02:06:18 GMT

Gotcha.

No line to curve grip conversion like a polyline as far as I know. Simplest way might be to add a PI, move the other PI, then fillet the two PIs.

Re: How to insert a curve into an alignment

ebaker — Wed, 11 Mar 2020 13:33:24 GMT

I extended the PIs and went to try the "Free Curve Fillet (Between two entities, radius)", I click on one segment of the alignment and it says "Selected entity must be part of the main entity." I turned off the corridor and put my alignment on defpoints, brought the alignment to the front, just to make sure I wasn't picking on the polyline where I want the alignment to be.

I really don't understand why this is so hard to add a curve to an existing alignment. Hopefully, I'm just overlooking something simple.

Re: How to insert a curve into an alignment

jae.kwon — Thu, 12 Mar 2020 01:19:24 GMT

I guess mainly the difficulty stems from us trying to maintain tangency (keep everything "free" instead of "fixed").

But yeah, the alignment segment tools are a little harder to use than it could be...

Re: How to insert a curve into an alignment

tcorey — Thu, 12 Mar 2020 12:59:08 GMT

"Selected entity must be part of the main entity."

Sounds like your existing alignment components might not all be pointing in the same direction. ? . If you label the alignment, does it label the entire alignment? If not, that's a sign.

A screenshot (or post your drawing) would help.

Re: How to insert a curve into an alignment

ebaker — Mon, 16 Mar 2020 12:44:38 GMT

dwg is attached.

Re: How to insert a curve into an alignment

wfberry — Mon, 16 Mar 2020 13:26:51 GMT

If I were doing this I would re-do the alignment. There will be problems with the first two curves coming from the north and also there are two non-tangency problems at the south.

1. You have a current centerline in your block. Use N-Copy and get the centerline polyline into your model space.

2. Explode the polyline and remove curves. Use a fillet of "0" to get you to a single polyline by edit the lines into one polyline.

3. Make your Civil 3D alignment by using the Alignment from "Create from Objects".

4. Then put in your curves using alignment tools.

Bill

Re: How to insert a curve into an alignment

ebaker — Mon, 16 Mar 2020 14:33:51 GMT

Thanks for the reply,

Putting in the curves is my original question. Regardless of the tangent issues, I was just trying to figure out a simple way to turn a straight segment of an alignment into a curve, without redoing the whole alignment. Without doing massive corridor changes and having that automatically update with the seemingly simple modification to the alignment. Simple, apparently, doesn't apply to turning a straight segment of an alignment into a curve.

Re: How to insert a curve into an alignment

wfberry — Mon, 16 Mar 2020 17:03:51 GMT

I agree with what you are saying, but normally we don't need a curve in a straight section. It is quite easy to make P.I.s and then introduce curves using the included alignment routines.

Bill

Re: How to insert a curve into an alignment

ebaker — Tue, 17 Mar 2020 12:17:31 GMT

That's pretty much my goal of posting the question. If inserting P.I.s into an existing alignment and then introducing curves using included alignment routines is the solution, then I do not know how to introduce curves using the included alignment routines.

Re: How to insert a curve into an alignment

wfberry — Tue, 17 Mar 2020 12:22:02 GMT

I was referring to making a NEW alignment derived from the existing block's centerline. Use Ncopy to get the centerline out of the block and into your model space.

Bill

Re: How to insert a curve into an alignment

jae.kwon — Tue, 17 Mar 2020 12:49:32 GMT

Looks like staying dynamic and tangent is not too much of an issue for you, since that is the polyline line->arc conversion.

If so, then just delete the one straight segment with the delete segment tool and add a three point fixed curve.

Might have to adjust region starting/end stations a little bit after but it shouldn't be a big deal.

Re: How to insert a curve into an alignment

Jowennl — Tue, 17 Mar 2020 12:57:15 GMT

Hi @ebaker ,

Thanks for sharing a sample dwg. Are trying to do something like the animated gif below?

I think you can just delete both lines and create a curve as fixed curve three points and just make sure you follow the alignment path which starts at the top as zero station. Then when you make the new alignment you can fix the tangent issue after the rebuild again.

SomethingLikeThis.gif

See attached dwg as well.

Cheers,

Jowenn

Re: How to insert a curve into an alignment

ebaker — Wed, 18 Mar 2020 15:31:45 GMT

I think this looks like what I need! I don't have time to try it out at the moment but it looks like what I wanted to get to.

Re: How to insert a curve into an alignment

lynn_zhang — Wed, 25 Mar 2020 05:29:38 GMT

Hello @ebaker ,

Just checking to see if your problem has been solved. Did you follow the suggestion from @Jowennl and did it work for you? If yes, please click on the "Accept as Solution" button in his reply so this helps other users in the community find the solution too. Thanks!

Re: How to insert a curve into an alignment

zshakir — Tue, 25 Jul 2023 15:34:05 GMT

THANK YOU FOR THIS TUTORIAL