How to insert a curve into an alignment

[ebaker]

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. 

[Jowennl]

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/Civi... 

https://knowledge.autodesk.com/support/civil-3d/learn-explore/caas/CloudHelp/cloudhelp/2019/ENU/Civi... 

[Jowennl]

Hi @ebaker 

Here's a sample animated gif. 

SampleAlignmentManipulation.gif

Another Sample.png

Cheers,

Jowenn

[jae.kwon]

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?

[ebaker]

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.

[jae.kwon]

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.

[ebaker]

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.

[jae.kwon]

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...

[tcorey]

"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.

[ebaker]

dwg is attached.

[wfberry]

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

[ebaker]

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. 

[wfberry]

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

[ebaker]

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.

[wfberry]

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

[jae.kwon]

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.

[Jowennl · Accepted solution]

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

[ebaker]

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. 

[lynn_zhang]

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!

[zshakir]

THANK YOU FOR THIS TUTORIAL