Step into the Present
In the past I’ve been a bit hard on AutoCAD® Civil 3D® and its lack of BIM features. If you are using an older civil software product you might want look past those critiques and see the benefits Civil 3D does offer. There are a whole bunch of improvements in the software to make the step forward worthwhile.
One of the biggest improvements is in how surfaces perform. No more of continually rebuilding a surface through a dialog box that asks you the same confusing questions each time. Civil 3D obscures many of the options in the surface properties dialog box, which you may choose to also ignore. Instead, the ability to right- click and rebuild the surface at will is available. While I haven’t had much luck in the actual use of rebuild automatic, it is available if you don’t mind waiting a second or two after each modification you make to the objects that make up the surface.
Another benefit of surfaces is the ability to add points along tangents and curves of polylines, 3DPolylines, and Feature Lines. This means you can keep the geometry of the objects whole without adding supplementing points before adding breaklines to a surface, which was an often used step in Land Desktop to provide better looking surfaces.
Speaking of Feature Lines, they provide a vast improvement of the use of 3DPolylines in Land Desktop. It’s now possible to have curves without tessellating the geometry before adding it to a surface. The tessellations are handled by the surface when the feature line is added to the surface as a breakline. It is possible to specify the tessellation distance when the feature line is added to the surface. The editing tools of modifying the feature lines are great. The tools encompass many of the calculations you’d want to perform. Need to figure out the high point along the feature based on an incoming and outgoing grade specification? Well, it’s in Civil 3D.
Figure 1: An unremarkable surface picture.
In Land Desktop I was never able to figure out how to modify an alignment. I’m sure there had to be a better way than deleting and recreating the alignment from a polyline. With Civil 3D those modifications are fairly painless. Need to add a PI point? Simply open the Alignment Geometry Toolbar, press the Add PI tool, and select the location of the new PI point (some rules and restrictions may apply; see product documentation for further information).
Station labeling updates after modifications to the geometry are complete. No more deleting and recreating the labeling—Civil 3D handles it for you. Of course, there are times when you have constraints in the alignment creation and Civil 3D can assist in maintaining those restrictions. With the use of fixed-type alignment segments (such as tangents and curves) it is possible to place the fixed segments and then tie into them using float and free type segments.
Don’t worry if you don’t understand the terms of free, fixed, and float—you can still use Civil 3D without using those terms and create alignments with PI points only with curves. There is even a command to facilitate this type of alignment creation. Note, though, that the power of Civil 3D alignments increases exponentially with an understanding of those terms.
Similar to alignments, profiles also have moved into the world of free, fixed, and float terms. There is still the ability to work old school with PVIs and vertical curves. If you do happen to create a profile with PVIs, you’ll want to add the vertical curves as float type vertical curves. Similar to older software products, the proposed type profiles are typically independent of a location in plan space. This means if you change the geometry of the alignment, the profile will not update accordingly. It still retains the original station elevation values; the station of the profile PVI does not adjust to be at the same location in plan view.
The last statement is important to recognize. I know when I was first introduced to the product, it was often stated that when the alignment changes the profiles change. Little did I recognize the difference between sampled from a surface profile and profiles created as a design. The profiles sampled from a surface do update when the geometry of the alignment changes. Despite this drawback, the advantages of this updating on the profiles is worth upgrading from Land Desktop to Civil 3D.
With points, you either love them or hate them. I happen to love them, mainly because I usually don’t have to contort point labels to be visible and non-overlapping in a drawing. Civil 3D has a wonderful way of grouping similar points together in Point Groups. Filters are applied to the points located in a drawing and they are then grouped together in the point group. The point groups may then control their appearance and label style. Don’t worry, there is the ability to override the appearance and label if you want the point to be different than what is specified in the point group.
The point group may then be added to a surface definition. Any additional points imported into a drawing, say from a later survey, will automagically be inserted into the point group. Then when the surface is rebuilt the additional points will show up in the surface.
If you design a surface by using points you’d love the above mentioned capability. This feature will save you numerous steps by not having to manually rebuild the surface after creating new points.
When designing a project that utilizes a linear type approach, such as some roadways, levees, and bike trails, then corridors are the way to go. Corridors make it easy to utilize a section-based design workflow. The geometry required for the sections are most easily created by the use of assemblies and subassemblies. Assemblies are the container for the section geometry. The subassembly objects are the individual components that make up the geometry. Subassemblies represent curbs, pavement, landscaping, or other geometric shapes. These shapes may have targets for both the horizontal and vertical changes in geometry, providing greater flexibility.
Often there are designs that demand greater design requirements than can be performed with the out-of-the-box subassemblies. That is where Subassembly Composer comes to the rescue (at least for Civil 3D 2012 and 2013).
Subassembly Composer allows you to build complex designs that would be difficult otherwise. I’ve used Subassembly Composer to consolidate curb and gutter types for agencies. This way I don’t have to replace subassemblies if they change; I change the property of the subassembly to reflect the new curb type.
In this article I’ve shared some of the features I do like about Civil 3D and why I use the product in production. I’ve been a long-time user and blogger, since Civil 3D 2007.
Figure 3: Assembly in Civil 3D.