Corridor Bowtie Resolutions in Civil 3D 2021.1

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Autodesk made some quiet and undocumented changes to the default Corridor properties in the latest Autodesk Civil 3D 2021.1 Update. The Civil 3D 2021.1 Update’s new separate Inside and Outside Corridor Bowtie Settings for both Tangent and Arcs corner intersection resolutions. These changes can and do affect the default corner resolution behavior in Corridor Baseline Regions.

These important Corridor default Automatic Clear Bowtie Options Settings properties changes are not currently mentioned or updated in the Civil 3D 2021 help files.

Corridor Bowtie Resolution Behavior in Civil 3D 2020.4+

Is this is a new Update change that slipped out in the final Civil 3D 2021.1 Update public build? 
Not so fast...History at Autodesk can be revised. Grin.
Funny. All of a sudden after this post went live this change became a documented Civil 3D 2020.4 Update change.
It appears the Automatic Clear Bowtie Options Settings were changed in the Civil 3D 2020.4 Update, but were not included in the initial public build of Civil 3D 2021.

You can run into the issues covered in this post upgrading drawings to Civil 2020.4+ and to Civil 3D 2021.1.
The improved Corridor Bowties behavior changes are still a good thing.


A Simple Site Grading Corridor in Civil 3D

Mind you.
The issues discussed here are not a reason to avoid the use of the powerful Civil 3D Corridor tools in site grading and parking lot design.

The code is rarely our production problem in Civil 3D.
What we learn to do with the tools is the more significant issue.

New Automatic Clear Bowtie Option Results

If you employ the Corridor engines Corridor Bowtie Settings and/or the Corridor Bowtie tools in your Corridor design process (and you should), you may experience different Corridor Bowtie corner resolution behavior results after the Civil 3D 2020.4+ Updates or the Civil 3D 2021.1 Update. Oh bother.

A Powers Play for Corner Defaults

Autodesk separated the default properties into Inside and Outside corners default for Corridor Bow Tie resolutions. 2 default Corridor Settings in Automatic Clear Bowtie Options default properties become 4. The Civil 3D Updates appear to successfully duplicate the old single defaults into two new defaults.
Sorry. These important Corridor Settings are still a bit annoying to check in the interface.

These new and potentially useful Corridor Settings may mean the Corner Bow Ties do not resolve as they did previously in Civil 3D 2021 or Civil 3D 2020 prior to Update 4. A rebuild of the Corridor after an Update can break corner resolutions.
What the….

The Corridor Settings, the automated Bowties fix code, and results changed. They got better, so why the new hassle?

See the recent Civil 3D Grading Multiple Baseline Mechanics post and video for more about managing Corridor Bowtie resolutions better.
To put that simply for our management of Site Grading Corridors – Less can often be more.

Alignment/Profile Design Control or Feature Line Design Control

For both forms of Baseline horizontal and vertical design control the Tangent-Arc and Arc-Tangent corner intersections seem to resolve as in previous Civil 3D Releases and Updates. Whew. That had me worried too.
Yet we can still have issues with these corners in these Baselines if you upgrade the drawing with a Corridor.

It appears in most cases the updated automated Corridor Bowties appear to work better for Alignment and Profile Baseline design control for both Inside and Outside Tangent Tangent corner intersections. Hoorah.
Once again…But not always.

Corridor Baselines with Feature Line based design control often seem to produce more issues resolving corners. Dooh. Due to Frequency issues in the Extracted Feature Lines you are more likely to be forced to manually fix the Corridor Bowties with this form of design control in a Baseline.
That ends up being significant, but not so obvious.

See the Multiple Slope Site Corridors in Civil 3D post and video and the other linked posts.

The automated Frequency application that makes the automated Corridor Bowtie correction work is currently happening exactly as it did previously for Feature Line based Baseline design control.
Yet it still does not happen all the time.

See the Civil 3D Corridor Site Design Considerations post and video to learn more about how properly managed and applied Region Frequencies can make your Corridor work better and easier in Civil 3D.

All the Automated Corner results we experience can be different. This is madness?

Fix and Resolve

If you discover issues with Corner Resolutions in your upgraded Corridor in 2020.4+ or 2021.1, the reason for the issues cannot be found in the most likely places.
Sad to say that the fix to this problem (which appears to be intermittent but is not) took a bit of work to root out.

Frozen Manual Bow Ties

Hmmm? Doesn’t that sound like a microwave pasta dinner?
“Honey? How long has this meal been in here?”

Any previously applied manual Corridor Bowtie fixes in any Corridor Baseline are the most likely cause of the problem.

By default, any new update in the Civil 3D code tries hard not to smash our User data.
That conforms to the normal, and usually friendly Autodesk Golden Rule.

Our existing user-built, manual corner fixes are exactly that kind of thing.
Then we get to experience the…

Law of Unexpected Consequences

Keep in mind that the Manual Bowtie fixes are kept in a separate Fixit list for the entire Corridor. Put another way…Fixes are not collected and processed by Baseline but by Corridor. Our existing and previously stored manual corner fixes in the Corridor collection know nothing about the new code and new Settings.
"New wine in old wineskins" says it all.

Here’s the Instant Replay in slow motion:

  1. We update the drawing to 2020.4+ or 2021.1
  2. The Baseline is marked out of date because the Corridor Settings are new
  3. The Corridor is flagged for rebuild – it is out of date
  4. Our Corridor rebuild resolves Baselines yet these seem to totally ignore the new Automatic Clear Bowtie Options Settings.
    The rebuild results may produce the loss of all corner resolutions in some Baselines and/or strange mixed results because of the previously stored manual fixes.

The existence of any manual Bowtie fixes appears to wall off any automated changes by the changed Corridor Settings.

Manual Bowtie fixes in one Corridor Baseline can and do appear to effect automated Bowtie processing in other Baselines.

Hopefully, you will never experience this unexpected difference. If you do, this is relatively easy to fix.

The Corridor Bowtie Tools Method

Remove all the previously applied manual fixes with the Restore Corridor Bowtie tool.
Do this for each and every Baseline that might contain a manual fix.
Yes. If you have Code Set Styles that visualize what’s going on, it helps a lot.
Reapply the Clear Bowties manual fixes that are required.

The Assembly Redefinition Methods

A redefinition of the Assembly(ies) employed in a Baseline Region forces the Civil 3D corridor engine to abandon the old manual Bowtie fixes for that Baseline all together.

We can temporarily redefine the Assemblies employed in the Baseline Regions.
Remove a Subassembly; Save; Rebuild the Corridor; and then add back the Subassembly.

You can also simply replace the Assemblies assigned to the affected Regions to force Civil 3D to abandon the out-of -date Corridor Bowties list. The Subassembly contents of the Region Assemblies may matter.
A  managed Set of Assemblies that work together continues to make a lot of production sense.

The proactive identification and thoughtful management of the current State of a Corridor matters.

Do you still have problems with Corners in your site grading and parking lot Corridor Baselines?

Replace Feature Line Design Control

Extracted Feature Line based design control can have too much data in the wrong places in either or both the horizontal and vertical control to resolve well at Baseline corners.
Remember that Baseline Region Frequency results get passed to the Extracted Feature Lines.
For better automatic Corner resolutions often less is more.
Obviously, we can manually edit the Extracted Feature Line to simplify things, but that means even more manual edits to track and maintain.

How to Fix Finicky Feature Line Baselines

Leave the Feature Line based Baseline alone. Turn the Baseline off in the Corridor collection. You may need to see and recall what you did before while you build the fix.

Now build a new Corridor Baseline with the design control that Civil 3D prefers to eat.

The Civil 3D Corridor engine remains tuned to and prefers Alignment and Profile Baseline design control. A conversion of extracted Feature Line based design control Corridor Baseline geometry to Alignment and Profile pairs usually does the trick well.
See the Create Alignment From Corridor command.

Remember that you can also employ a temporary simpler or detailed Surface to generate the vertical control for an Extracted Alignment’s Profile. You can also simplify the Extracted Profile by manual edits or by tracing over even parts of multiple surfaces in a Profile View.

Another Feature Line to Alignment/Profile conversion method that works is to generate a Quick Profile View of the Feature Line and then Export to LandXML the selected Profile from the Profile View.
The Import of the LandXML will generate both an Alignment and a Profile copy of the Feature Line.

This LandXML method also works to easily produce and move project-based DREF sources of the design control to generic NoStyles data reference containers.

Project Managed Design Control is Better

This Alignment/Profile method of Corridor Baseline design control also includes the production advantage that can make that important Corridor design control much more project based via managed Data References.

See the Civil 3D Data References in Site Grading Corridors post and video for all the Why, How, and When of that Civil 3D method and practice.

Yes. The Framework for Civil 3D can produce Complex Multiple Baseline Site Grading Corridors and publishable output results right out of the box.
Can your Civil 3D Templates, Civil 3D Styles, and Civil 3D resources do that?

The Wonders of Managed Style Choice in Civil 3D
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