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Inside the Corridor Feature we Autodesk Civil 3D users get better horizontal, vertical, and cross section control,  better design round trips, more design control options, better project-based quality control, and more forms of data output. This significant list of production benefits makes the small amount of extra work that is required to employ a Corridor to create our civil engineering design, well worth the effort.

The Good News - This is not rocket science.

Learn to Cook with Corridors

Cookin’ with Corridors is a learnable skill.

I was hungry when I wrote this post. Chef skills never truly die. If you whack up a few big swordfish, tons of other fancy fish, and more than a few beef butts, the picture and the skills stick with you. I updated this post because the topics and the metaphor expressed here are timeless and tasty too.

Autodesk has delivered many new and improved tools in Civil 3D to make the approaches discussed here a much more practical since I first wrote the initial version of this post. These help make Corridor design skills a functional daily production reality in Civil 3D.
A Visionary Post? You tell me.
To Cook with Corridors still makes sense.


Dynamic Civil 3D Intersections

This video classic from the site speaks volumes. It is a wrap up outtake from the famous Stop the Wizard video. Yes. There are indeed some new nuances now available in the Intersection Wizard.

Complex Corridors from Intersections

I tend to employ Civil 3D Intersections and the Intersection Wizard tools as often as possible. Many civil design challenges represent point to point problems with similar offset design control-based solutions in between those same critical locations.

Utility ditches come to mind. We can employ an Intersection to produce useful design control quickly where we might never initially expect that a formal intersection would work.

“Where we are going...We don’t need any roads.”

It is just as important to also recognize that we may not want all of that automatically generated Intersection horizontal and vertical control anyway. After all, 80% of a solution resolved more quickly is faster.

“It is easier to edit than create.”
I employ the Intersection Wizard in a step-by-step fashion because I am lazy.

“It is easier to delete unwanted control than the recreate all the control from scratch.”
I detest taking the extra time to create all the related horizontal and vertical control the hard way.

The Intersection Wizard can save us time and energy when carefully and thoughtfully employed. Those principals are the subject for many other Corridor design posts and videos on this site.

As the World Turns

Way back when in the Civil 3D 2018+ releases, Autodesk introduced curve based Connected Alignments, Corridor Feature Line Baselines, and Slope Controlled Offset Profile tools. These tools substantially add to the design capabilities and potential variety of the Corridor design solutions available to us. The new tools also change some very fundamental Civil 3D usage patterns and mechanics (workflows) in the process.

Connected Alignments

The creation of individual Connected Alignments between Alignment and Profile pairs becomes quicker and easier task to train and learn than the many nuances of the Intersection Wizard and its interfaces.
Recognize that the separate tools are complementary not competitive in Civil 3D.
Neither is really a direct replacement for the other. Neglect neither.

The Civil 3D 2022 release introduces substantial design control nuances to the Connected Alignment tool and its design control definition with the introduction of segment-based patterns to the Feature. Connected Alignments became more like Curb Return Alignments and yet at the same time deliver more diverse geometric solutions for the complex lane control problems that highway design requires.

We have to ask, "Can we employ Connected Alignments with offsets from the Centerline Alignments to connect Offset Alignments to effectively produce Curb Returns?" Now that's worth a go, don't ya think?

I bring up Complex Corridors (Multiple Baseline Corridors or Multiple Dynamic Baselines in Autodesk speak) built between Intersections because the process of creating a variety of main dishes makes us think about and then execute our Corridor modeling in new and innovative ways.

When we employ Intersections and/or Connected Alignments and Feature Line Baselines, we must learn to create and manage the shared project-based DREF design control in multiple Baselines with multiple Regions with an entirely new level of Civil 3D skill.

How Many Baselines Do We Need?

This is like the infamous training question about Existing Surfaces,
“How many existing surfaces are there in a project?”
Some people answer, “One.” 
The skillful Civil 3D user replies, “As many as we need.”

Something Smells Fishy

The Civil 3D Corridor seems to be demoed and frequently taught employing salmon steak Assemblies to Regions. Take the big ole fillet of red fish and chop it cross wise into steaks. We could also call these pork chop or tenderloin Assembly based Regions. Perhaps you prefer the other white meat, beef steak, or beefcake analogy instead.

Cook It Up

We think about Corridor Regions as horizontal breaks in the structure of the Corridor. That is only part of what a Corridor Region does. Assembly application in the Region is the more substantive issue and nuance.

All too often we do tend focus on overly complex (across the entire grain) Assemblies made up of lots of Subassemblies. This classic roadway template like approach to Assembly construction, Region application, and management does work to solve many classic civil engineering problems.

Complex Assemblies with many Subassemblies (or complex PKTs) may also serve to make the management of all the intricate details of many civil engineering design problems more difficult.

This focus tends to miss the true depth of possibility at our fingertips from right inside the Civil 3D Corridor.

The Corridor in a Design Manager

The Civil 3D Corridor Feature is a design management tool. When we learn to cook with Corridors, we discover that a Corridor can be easily adapted to provide us with a number of diverse divide and conquer strategies.

Corridor Baseline and Region functionality allows us to temporarily reduce or increase the design complexity to test and deliver more design options and/or perform quality assurance and control.

Do you work at Corridor design with all the Baselines, Regions, and corridor Surfaces turned on all the time?
Learn to employ those checkboxes in the Parameters and Surface tabs of the Corridor Property dialog box. The ON/OFF checkboxes are there for more than one reason.

What about Linear Ribbons?

Please, excuse my word play in Civil 3D speak.

Who said we cannot separate the roadway, levee, or channel design itself from the side design conditions?
Instead of steaks we get ribbons or chicken strips when we employ multiple Baselines in this fashion. The classic Non-Linear Corridors video employs Ribbon like design control to perform some interesting Pond design mechanics based on a snake and tail Alignment and Profile pair and Offset Alignments with a Widening.


Basic Spot Label Style Expression Set Rewards

The first few minutes of this more recent Label Style Expression Set video outline the current Corridor design details and mechanics of the Pond design as outlined above.

True, the Civil 3D Corridor engine is not quite as adept or easy to use this way initially. We do have an experiential learning curve to slice and dice through. Repetitions matter.

We are going to have a bit more manual maintenance of the Corridor output to maintain the critical relationships in the related Alignment and Profile design control. Corridor Feature Line Baselines help more than a bit. The Civil 3D tools to proactively perform these unnatural controlled acts are in the Ribbons.

How to use and manage the Corridor Baseline, Horizontal Baseline, and Vertical Baseline Target control well takes practice.
Yes. Where we keep the project-based DREF (referenced) control we create and manage matters.
If we practice the learnable techniques, we’ll get better at it quickly. Here are some of them in detail…


Site Grading Design Shared Control

The Baseline ribbon technique often makes a lot of sense as a method to manage the more complex details that come along in many projects. Here a ditch, here a wall, here a guardrail, here a pond, etc. Our new Baseline ribbons can be easily carved into more manageable strip steak Regions.

Kebob Regions

We can extend the strip steak or chicken strip (Baseline ribbon) approach. We can do shish kebob Regions once we get the hang of the multiple linear Baseline concept and techniques.

I should put that another way. No one said we cannot employ the exact same horizontal and/or vertical control in multiple Regions down a Baseline ribbon. First, you want a piece of meat from this Baseline Region; next an onion from that Baseline Region; then a tomato from that Baseline.

We can also employ Civil 3D stock Conditional Subassemblies and the related design control to create the same Kebob Region results. Where do we want to manage the design optionality and complexity? Inside a complex Assembly or custom PKT or inside the Corridor Baseline and Region Parameters and Region Targets.

Look carefully at our Civil 3D grading problem.
Do we often switch between a number of standard partial cross sections with a few exceptions?
Might not even those exceptions also benefit from some systematic isolation by a secondary Baseline and Regions? You bet!

Baseline Cordon-Blue

Many Assemblies use Subassembly tools that include stacks of Subassembly or PKT Links. The Corridor engine can produce and manage multiple Baselines with stacks of Assemblies too. Sometimes we want the trenches with the pavement sections and other times we do not.

We could call this the lasagna or cordon blue multiple Baselines approach. I tend to build and test these parts in a temporary Corridor(s) and then include the tested results in a more managed Corridor model when I’ve tested and finished them. We usually do have to bake and cool the cake before we decorate it. Don’t we?

A simple Stripping Assembly is easier to deal with and to QAQC this way.
When we need to construct them, the staged earthwork surfaces or intermediate surfaces are only a new Corridor Baseline and Region away.

Presentation Matters so Preparation Matters

We do need better choices of Civil 3D Style tools to be able to visualize this sort of detail.
Just how many Code Set Styles, Alignment, Profile Styles, etc. are you going to want to have available to do this sort of work?
Maybe a standardized approach to Civil 3D Style and some user-friendly management of all of that is something to consider? 

Frankly, very few people have the time, money, and experience to build this sort of integrated detail from scratch. That is what we do. You don’t have to reinvent the hamburger and the chicken sandwich.

The Jump Kit product includes the largest collection of fully integrated and tested Civil 3D Styles you can get anywhere – Jump Kit is all about production performance, better design optionality, and more robust and adaptive standards for Civil 3D.

Feast and Enjoy!

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Book of Alignments Posts

Updates, additions, and fixes to the posts in this series are on-going.