603 - 5885 1250 (4 lines) info@mes100.com

AutoCAD is NOT Civil 3D

Background and Motivation #

It all started when a user came to us with an AutoCAD drawing, he seeked our advice on how to properly model the site design in MiTS software. His task: verify the earthwork quantity results submitted by a consultant.

This is how a keyplan section of the drawing looks like:

At a first glance, this seems like a straightforward design, after all, all the platform levels are properly indicated. PL indicates Platform Level, so PL25.45 means Platform Level 25.45 m, RL means Road Level, so RL24.80 means Road Level 24.80 m. It should be simple to do the modeling and confirm the results, right?

Alas this is not so. Because as we discovered, the drawing in AutoCAD and the actual drawing in Civil 3D looks very different; you can’t properly model Civil 3D entities if all you have is just an AutoCAD application. 

Civil 3D drawings are dangerously misleading, with AutoCAD #

When the user came to us, we opened the drawing in Civil 3D ( luckily we have one!). We immediately saw why he was struggling with getting the same results as the consultant did. That’s because all he had was AutoCAD, which is missing a lot of Civil 3D entities like Feature Line, breaklines, and boundaries.

Feature Lines aren’t shown #

The drawing used Feature Line for modeling, but AutoCAD couldn’t show it

The feature line in Civil 3D that is missing in AutoCAD

In AutoCAD the same feature line is missing

Without the feature line, there is no way to construct the Surface properly and the TIN surface he constructed would be different from what he saw in AutoCAD. Which brings us to the next point.

TIN Surface Triangles are not shown #

In Civil 3D, the calculation of cut and fill is dominated by TIN surfaces– surfaces with triangle elements formed together. The first step to calculate cut and fill, is to form two comparing surfaces.

So we have to get the TIN surfaces out first. Despite the fact that you see “flat” platforms in the drawing as shown below, they are not TIN surfaces.

Let’s turn on the Coordinate tracker and hover over the “flat” platform to see the z coordinates. They are different from what is indicated; they are not even flat. 

For Example 

The polyline below show an elevation of 24.5

However, when we use a coordinate tracker along the polyline, the Z value is inconsistent. This demonstrates that the polyline is not flat.

Why? To investigate, one needs to turn on the Triangles component, under the Surface Style->Display tab. This is where you can see how Civil 3D constructs the TIN surface; the flat platform is not a rectangle object, but rather two triangles with uneven z values. As far as cut and fill result is concerned, it’s the triangles that count, not the polylines.

But the triangles, the TIN surface and Surface Style are only available in Civil 3D and not AutoCAD. 

AutoCAD can’t display all the information that Civil 3D has, so no wonder our poor user couldn’t get what he wanted.

What about the Platform Level indication? #

Referring to the above image, the Civil 3D designer “helpfully” labels the Platform Level with a prefix “PL” in front. This actually creates more confusion, because this is not the actual level Civil 3D uses to construct the TIN surface.

Instead, the polylines’ z level that forms the boundary around the indication is used to construct the TIN surface. The polylines are 300 mm lower than the indicated Platform Level in this case. If you think from the point of the earthwork designer this actually makes sense: when we do the earthwork, we often need to excavate an extra 300 mm from the Platform Level ( dubbed the “earthwork level”). Which is why the actual Level is 24.50 instead of 24.80m.

The problem is that the earthwork designer might not have anticipated that people would actually use his drawing for validation, therefore he left the ambiguity in and created all loads of confusion.

Conclusion #

By now, it should be clear as daylight that opening a Civil 3D file in AutoCAD is a no-no, because Autodesk won’t warn you that you are using the wrong application to read the file, so you simply don’t know what you don’t know. The conclusion is inescapable: using Civil 3D files as the information exchange medium and without explicitly telling all parties so, is dangerous and also somewhat irresponsible. As an engineer, it’s your duty to ensure that your communication is clear!

My suggestion to Autodesk: please come out with a separate file extension for Civil 3D files, to avoid confusion.

UI Cluttering and other issues in Civil 3D #

But besides the file exchange problem above, we also notice there are further problems with using Civil 3D for engineering design purposes. The fact that it is sold under the brand name “Autodesk” has no resemblance to the quality of the software.

Civil 3D is not built for Civil Engineers #

Despite the name, Civil 3D is not natively built for civil engineers, it’s just a plugin for AutoCAD; so Civil 3D is more of a drafting software than an engineering software. This means that the whole architecture is severely constrained by the AutoCAD architecture. AutoCAD nomenclature and concepts also heavily dominate the Civil 3D interface, to the detriment of the Civil 3D usability. 

Just take a look at the interface from the viewpoint of an engineer:

What do Insert, Annotate, Modify, Analyze… and all even mean? Maybe they make sense to draftsmen, but they are not making sense to civil engineers. I just want to do my Civil design, and I expect to see Road, Earthwork and drainage related modules indication, but the Civil 3D UI components are aliens speak to me. 

An engineer can still get the civil job done in Civil 3D, but not before he internalizes all the draftsperson nomenclatures, and overcomes the CAD-Civil impedance mismatch.

TIN Surface doesn’t work great with manmade terrain. #

For Earthwork, the Civil 3D design concept revolves around the TIN surface, which works great with natural terrain representation, but doesn’t work too well with manmade terrain that involves drops, walls and slopes

To cater for this need, Civil 3D came out with tools like breaklines, grading, boundaries and feature lines. But all these are just unintuitive hacks to “hack” away the TIN surface so that it represents man made terrain. It doesn’t map directly to how we would design our platforms, roads and ponds.

Furthermore, they all look the same with polylines and other CAD entities. You always have to be additionally vigilant and ensure that you are working with Civil entities like Surface and not some random entities that look like Surface entities. The integration with AutoCAD brings a lot of benefits to Civil 3D, not least because you can fully leverage the AutoCAD codebase and features, but the tradeoff is that you inherit the baggage of AutoCAD.

The great decoupling of entities #

Another sign that Civil 3D is just a plugin for AutoCAD is that for Civil entities like Surface, it has a Style property to manage the appearance, as opposed to layers. In a perfectly designed software, civil entities don’t really need layers, a Style is all that you need because it subsumes the layers. 

But because Civil 3D inherits from AutoCAD, it also inherits the properties it doesn’t need, and hence causing confusion, even ( or especially) to the AutoCAD veterans: Why are the layer settings no longer controlling the appearance of my Surface? The answer is that you have to click on the “Edit Surface Style” instead of “layers” in order to change the appearance. But you will need to do some unlearning and relearning to fully grok this point.

For example:

The selected surface is under C-TOPO based on the table properties

Edit the polyline layers

FeatureLayersEdit Surface Style
Right click at the surface selected
Even though we already change the layers color at the layers properties, the color of the polyline is not changed at the display.

However if user using this feature it will change the properties and the display of the surface

Not only that, the Civil 3D entities are generally decoupled from CAD entities. Take for an example, the Mesh/3D Face/polyline entities that you use to generate Surface are decoupled from each other. So if you change the polyline entity’s elevation level, you will have to somehow regenerate the Surface by re-adding the polylines as the source of Points. This is just another constraint imposed by the plugin architecture that is unfixable. 

Biggest gotchas: Autodesk doesn’t care about you #

Those who are working day in and day out with Autodesk products will concur with my assessment: Autodesk doesn’t care about the users. Since switching to the subscription model, AutoCAD has been without fail increasing the price, with absolutely no increase in product quality. Autodesk “rent seeking” behavior infuriated people so much that it has led to calls for an EU action. 

But here we are not here talking about their rent seeking behavior. The issue that concerns us most is the way they treat their users and plugin developers– the ones who pay their salary– by simply failing to support us properly when we need help.

There is no dedicated Autodesk support, only community forums. There you can find unpaid volunteers who are doing an excellent job in supporting users who use Autodesk products. But since they are not being paid, there is no guarantee that they will give correct answers or even give any answer at all. 

If you want to report bugs or get Autodesk to respond to you, tough luck. You need to go through the following procedure: 

  1. File an issue on the community forum
  2. File a private ticket to the Autodesk internal team to point to the issue
  3. Get your account manager to look into those issues
  4. Wait. Maybe after a few weeks they would get back to you. Maybe.

None of the engineers that I’ve spoken with ever use the Autodesk support system. My experience as a plugin developer who depends on Autodesk to clear up unclear documentations and fix bugs and to provide workaround is a story of grit, persistence and endless cajoling. I just have to say it’s no fun, and I wish no one has to go through the same ordeal as I did ( and still do!)

So how do we move on from here? #

Completely detaching yourself from Autodesk products or from DWG files may not be feasible. But to communicate our intent clearly and to protect ourselves, we need to be extra vigilant when we are churning out Civil 3D files, especially with regards to the Earthwork drawings.

First and foremost rule, you need to insist your receivers have a Civil 3D application so that the drawings can be interpreted correctly. Remember that Civil 3D and AutoCAD files are very different despite having the same extension!

Second, due to a lack of integration between the CAD entities and also Civil entities like surface, you as a design engineer have to ensure that all details are properly updated when you change your design. Remember to regenerate your TIN surface as you change your polyline, and remember to update your platform mark when you change the polyline level. And so on, and so on. You have to remember that you don’t just do the design, you have to maintain it and have the responsibility to ensure that those who get the drawing can understand it correctly.

Or you can switch to us, MiTS application. We do provide synchronization with Civil 3D in the form of MCIntegrator. 

We are not Autodesk #

MiTS is built with engineering workflow in mind #

MiTS has an Earthwork module, and unlike Civil 3D, it is not a plugin of anything. In fact, MiTS is built entirely around the civil engineer workflow, with the Earthwork module at its core. 

This means that the concept of platform is naturally supported– you can easily model different platforms and with drops in between them, you can generate slopes at just one click , you can design roads together with other types of platforms seamlessly.

The software will not fail silently when you do the wrong design or use the wrong application to open the file; we have verification checks in place to prevent you from shooting yourself in the foot. We also provide extensive reporting so that you can check the results in detail.

We also withstand the test of fire, people did challenge us, but we prevailed in the end

In short, our software fulfills the definition of “user friendly software”: it doesn’t lie to the engineers, it warns them when they are likely entering into pitfalls, and it provides outputs that allow for fast validation and verification

Our software is not dangerous to use. Yes, you can trust our output drawings– they are unadulterated DWG files, they read the same regardless of whether you are using Civil 3D or AutoCAD to open them. You can just use the output files ( even in 3D format) and recreate the designs in another earthwork software and you will get the same result. No catch, no hidden objects and no surprise.

We do provide support #

Phone support, email support, whatsapp support You name it. We take delight in talking to our users because they are the source of our inspiration.

A day may come when we fail you, but no, we will not fail you by ghosting on you, like Autodesk.

Powered by BetterDocs

× WhatsApp Help