AutoCAD Civil 3D 2008 (Cadalyst Labs Review)

Dynamic modeling transforms civil engineering design, documentation, and delivery.

Civil engineering is and always has been a three-dimensional process; 3D in design, 3D in visualization, and, of course, 3D in the actual construction of civil works on, over, and/or under real-world 3D terrain. Although several generations of modern engineers have mastered a system of 2D representation of 3D designs, the underlying work remains three dimensional.

If Roman engineers could have magically encountered a twentieth-century system of 2D representation, they likely would have been familiar with many of the principles and methods — especially the tedious and error-prone process of revising dozens or hundreds of drawings every time a profile or alignment had to be changed and edited along an entire aqueduct corridor. However, in the twenty-first century, civil engineers no longer need be burdened with the tedious processes of 2D design tools for 2D representation of 3D work. Modern software can manage consistent and coordinated 3D representations in computer form while presenting a 2D interface to design engineers via screen-based graphical input and output, as well as printed/plotted paper drawings (or their digital file equivalents) for project communication across the extended team from the office to the job site.

In building design, this multidimensional process of representation, with associated data or building information, has come to be known as building information modeling (BIM). Because no comparable acronym exists for the civil information modeling counterpart to BIM, Autodesk has wisely chosen the simple and descriptive name Civil 3D for its product. Unlike Revit, Autodesk's BIM model-authoring platform for architects and building engineers, Civil 3D is an Autodesk-developed product built as a native AutoCAD/DWG application. (Revit was developed by another company on a database technology entirely independent of and different from DWG and subsequently acquired by Autodesk.)

AutoCAD Civil 3D 2008

Of Autodesk's prior solutions for civil engineers, Land Desktop remains available as a separate product, but Civil Design and Survey are no longer available for purchase or renewal as separate products. However, "the full functionality of the historical Autodesk Land Desktop, Civil Design, and Survey software is now included in AutoCAD Civil 3D 2008," according to Autodesk. Users of Land Desktop should note Autodesk's use of the word "historical" as a double-edged sword: Civil 3D is and will continue to be backward compatible with Land Desktop using Land XML or project-import features, but I suspect Land Desktop will eventually go away as a standalone product.

Migratory Flocks

Autodesk would prefer to have its current civil engineering, survey, site-design, and land-planning customers migrate to Civil 3D. Such migration is not without challenges, however. Prior to Civil 3D, most land-design–related software mimicked the paper-based 2D workflow of hand drafting — substituting a computer interface of pick-and-click line work for manually drawn lines guided by T-squares and triangles. Many engineers practicing today learned to transpose their manual procedures to software from DCA, which became Softdesk, which was acquired by Autodesk and eventually evolved into Land Desktop.

Figure 1. With rich functionality behind a clean interface, Civil 3D supports creation of intelligent alignments and profiles. (Images courtesy of Autodesk)

The dynamic-model approach of Civil 3D is conceptually different in the design and documentation process, as well as procedurally different regarding the how and why of the program's picks and clicks. Both the conceptual and procedural transitions can be eased with the Eagle Point Task Navigator add-on (see "Eagle Point Task Navigator for Civil 3D" sidebar).

For street and road design, Civil 3D uses assemblies to generate cross-sections, with multiple cross-sections strung together along an alignment (figure 1) and profile to form a corridor. Because all Civil 3D objects are parametric, their parameters can be edited to associate with different alignments. Thus, to add a median along a stretch of road or to modify that median to add, say, a left-turn lane where the median approaches an intersection, a designer doesn't redraw the roadway but instead uses a series of alignments and profiles to control the horizontal and vertical placements of pavement edge, sidewalk, and so forth. Users also can override or make slight changes to designs by editing them in the cross-section view. The software then automatically redraws the roadway to reflect the new design. Like most parametric software, Civil 3D includes constraints, so that a design engineer can specify the stacking space for cars at the left-turn lane (for example), and the program again automat-ically redraws the roadway to accommodate the new design condition.

Figure 2. Complex designs, such as intersection islands or pork chops, can be created using interactive grading features.

The result is an inversion of the old-fashioned — that is, pre-Civil 3D — workflow. Design engineers traditionally drew a road in 2D and cut 2D cross-sections as well as a 2D profile. Those drawings added up to a 3D corridor, but all the dimensional integration was in the engineer's or drafter's head. With Civil 3D, the 3D integration is embedded in the software, which can produce the kind of traditional-looking 2D profile and cross-section drawings that many highway departments still expect to review. The payoff in Civil 3D comes — as it does with most parametric software — when design changes have to be made: change any aspect of the corridor, whether alignment, profile, or any cross-section, and Civil 3D automatically recalculates and redraws everything else affected by that change. Changes literally ripple through the design.

Eagle Point Task Navigator for Civil 3D

A Matter of Style

Treating design elements as software styles means that the style governs more than just the appearance of the finished drawings; it also determines design and production workflow. The same principles that apply in Civil 3D to road design also apply to creating complex features such as islands at intersections (sometimes called pork chops [figure 2]), stormwater detention basins, pipe networks for storm or sanitary sewers, and so on.

Civil 3D styles can be customized to reflect the specific preferences of any user regarding symbols and notations, linetypes, contours, slope arrows, and the like. Styles are collected in templates, which can be customized and varied by client, project, jurisdiction, and so on. Autodesk's Civil 3D Web site includes country kits to localize the program for template requirements suited to 16 countries (such as Japan, Germany, Australia, and the United States) but not yet for individual state departments of transportation (DOTs) within the United States.

Figure 3. Using views extracted from the dynamic model, production of conventional plan sheets can be automated in Civil 3D using intuitive wizards.

Despite its different design approach and workflow, Civil 3D still can produce all the traditional 2D documentation that reviewing agencies and contractors expect. A system of viewframes can extract any desired 2D view from the dynamic model. Views are assembled onto sheets via a create sheets wizard (figure 3). With two-way associativity maintained between sheets and the model, edits in any location or view are reflected in the others.

Change Is Good

As has been the experience of architects and building engineers with BIM, Civil 3D requires civil engineers to rethink and reorganize their processes and workflows — not just internally but also in how they relate to surveyors, geo-technical engineers, landscape architects, and so forth. The style-based design and documentation automation and change-management features of Civil 3D make the process transition worthwhile for any member of the land-design team. In my consulting work with design firms, I see that the more of these disciplines a firm combines under one professional service umbrella, the greater the practice benefit of Civil 3D's integrated, dynamic-modeling approach.

Civil 3D 2009

Overall, for those not presently using Civil 3D, the 2008 version is worth the switch. For engineers who've already switched to Civil 3D, the 2008 version offers some welcome refinements (and the forthcoming 2009 version will offer even more, see "Civil 3D 2009" sidebar). Highly Recommended.