Over the past year or so, 3D modeling has become the “in” thing. A recent industry survey polled civil engineers as to which technology they think will have the greatest impact on their profession in the next five to 10 years--and 3D modeling was No. 1 at 31%.[1] I also noticed that the January issue of Site Prep had at least nine advertisements for data prep services, and another half dozen ads offered data prep and modeling software.

In my role at Carlson College, the training division of Carlson Software, I have observed that, of the more than 30 courses we offer to the engineering and construction industry, the most requested course in the past year has been our CAD-based 3D modeling course. Over the years, we have transformed our 3D grading course into a 3D modeling and data prep course. Our customers’ demand for this class has coincided with the maturing of GPS machine control offerings on the market. We have altered the curriculum and data sets used in the course so that they are more applicable to contractors who interpret designs into 3D models or elevate 2D drawings into 3D. As a result of these alterations, we have had a preponderance of contractors in these classes during the past seven years, mainly because they realized that engineering firms are not readily producing the models required for GPS machine control equipment.

A couple of years ago, I noticed that my classes were filled mostly with contractors but that there were often a few attendees from progressive engineering firms. And in the last six to 12 months, engineering firms have increased their attendance in these classes. They are beginning to ask how they can replace the revenue they have lost from the decline of traditional stakeout. Now engineering firms are increasingly finding that they need to prepare 3D models, take liability for them (in some states, they don’t have a choice) and service the construction contractor better.

Establishing the Business Model

In many of these sessions where contractors were the majority of the attendees, I have asked if they would prefer that the engineering firm provide 3D modeling data. The answer was resoundingly yes, though, often qualified with “if the developer will pay for it.” That makes sense since the developer is the one who will gain the most when the design moves directly into the field. And the fewer people who interpret the design, the fewer hands that are involved in the 3D model preparation. The contractors can then spend their time pushing dirt and material while the engineer takes responsibility for the design. Of course, in order for the engineers to take responsibility for the data, they need to charge a fee to cover their liability.

To move into 3D modeling, a firm must establish a business model that encompasses the actual technical task and covers the following aspects:

• Contracts and agreements should be modified and updated to reflect this new type of work and include the delivery mechanism and vehicle for handing over the data, certifying it, and logging to whom it went, how and in what condition and formats. Additional consideration should include items with regard to intellectual property rights, commonly known as IP.

• The marketing department should be fully aware of this new resource and trained to speak intelligently about it to customers.

• Project managers should be attuned to the new challenges that will accompany this task, including using software that allows for easy 3D input and rapid modifications to the data based on change orders; finding and/or training staff to work naturally in 3D; and providing a turnaround response time to the client when an issue arises. If a change occurs on a project that affects the 3D modeling data, the engineering firm will have to effect that change and turn it around very rapidly for the customer. Project managers must also realize that dozers may be on the jobsite burning gas while waiting for a solution.

Once a design firm establishes its business model for offering this service, work can begin and revenues can be generated. I recommend that engineering firms build a relationship with one or more local contractors and work with them to hone precisely what is needed for machine control data prep. Such a partnership will pay dividends.

Another aspect that requires attention is the use of 3D in the design department. 3D projects should be pegged up front. If the design staff works in 3D to accomplish its own tasks, everyone else down the line of the project lifecycle will benefit, as well. In addition to machine control projects, other projects slated for 3D might include contentious projects where many reviews and modifications are anticipated, or when renderings and animations are expected for public or other communications.

Performing 3D Layout Functions

Enlarge this picture Figure 1. Entering a 3D breakline

Certain functions are invariably used in 3D layout work; the following brief overview of six common functions and how they work should be useful.

These six functions can usually be accomplished in all of the major civil engineering software applications currently on the market. The software tracks the user’s progress while simultaneously providing feedback as to what result occurred. I have heard many engineering design managers say they don’t want their staff designing in 3D because it is too hard or takes too much time. To prove that this isn’t necessarily true, managers can track this audit trail to see that these are not difficult functions to perform. The following examples include the output of the AutoCAD command line so both the prompt and user response can be seen. The user’s input is shown in bold typeface; comments are shown in italics.

Function 1: The ability to generate three-dimensional line work that is both linear and curvilinear. Figure 1 shows an access road edge that is designed from the existing ground elevation indicated at 456.00 and extends in a northeast direction. The first linear leg of the edge of pavement rises at +2%. When it comes to the point of curvature of the road, the slope slows to +1% and then comes out of the curve and extends again, also at +1%. This type of command allows for the layout of any object in 3D where the elevation is governed by slope, elevation or other vertical specifications. Note that, except for initiating the command, the user types six characters to indicate this 3D breakline--not a difficult task.

Command: 3dp

Continue/Extend/Follow/Options/ ]: _nea to [the user snaps to a contour where the road begins]

Interpolate/Object/ <456.00>: <enter>[accepted by the user as correct]

Z: 456.00

[Arc/Close/Distance/Follow/Undo/ ]:

Percent/Ratio/Interpolate/Degree/Object/ <456.00>: P [indicates that a percentage will be used to indicate desired slope]

Ratio/Interpolate/Elevation/Degree/Object/ <0.00>: 2 [A 2% slope is desired and the software responds with visual feedback so the user can see if he or she is on track for a satisfactory result, shown below.]

Z: 460.46, Hz dist: 223.04, Slope dist: 223.09, Slope: 2.0% Ratio: 50.0:1 [feedback]

[Arc/Close/Distance/Extend/Follow/Line/Undo/ ]: a [denotes that an arc is about to be placed into the road]

Radius pt/radius Length/Arc length/Chord/Second pt/Undo/
number>]: s [indicates that a point on curve will be used to define the curve’s geometry]

Second point or point number: [the second and third point is indicated by the user]

Endpoint or point number:

Ratio/Interpolate/Elevation/Degree/Object/ <2.00>: 1 [changing to a 1% slope]

Z: 462.23, Hz dist: 2.97, Slope dist: 2.97, Slope: 1.0% Ratio: 103.1:1 [feedback]

[Arc/Close/Distance/Extend/Follow/Line/Undo/ ]: L [switching back to the linear entity type]

Enter or pick distance [a point is picked by the user to indicate distance]

Ratio/Interpolate/Elevation/Degree/Object/ <0.00>: 1 [maintaining a 1% slope]

Z: 467.10, Hz dist: 486.79, Slope dist: 486.82, Slope: 1.0% Ratio: 100.0:1 [feedback]

[Arc/Close/Distance/Extend/Follow/Line/Undo/ ]: <Enter>[terminates]

Enlarge this picture Figure 2. Draping an object.

Function 2: The ability to drape objects onto a surface. In Figure 2, a building is placed into the drawing at the correct elevation using the pline command and setting the building to the desired elevation by snapping to a contour or by using AutoCAD to move it to the correct Z value. A retaining wall is required on the east and north sides of the building. A pline is also drawn at the location for the retaining wall; without worrying about the elevation, a default of zero is used. The goal is that the linework should be draped onto the existing ground such that the bottom of the wall is clearly on the ground. Another use of this is to ensure tie-out to existing ground by draping a polyline within a certain buffer distance from the property line. This will guarantee that no proposed activity will occur outside the draped object. The TIN algorithm will tie other proposed objects to this draped object thereby assuring that the project ties out to natural ground at a satisfactory location. The following information tracks how to drape the object onto natural ground thereby setting the wall at ground level. Again, this is very easy to perform. Note that the “grips” shown in the example indicate the places on the pline where the ground was sampled and where it elevated the retaining wall to reside directly on the existing ground surface.

Command: 2dto3dpf

Loading edges…

Loaded 2564 points and 7490 edges

Created 4927 triangles

Select polylines to convert. [user selects the original pline at elevation 0.0]

Select objects: 1 found

Select objects: <Enter>

Use current polyline elevations as vertical offset from surface [Yes/]? <Enter>

Keep existing polylines [Yes/]? <Enter>

Set layer name for converted polylines [Yes/]? <Enter>

Converting polylines…

Elevated 1 polylines.

Enlarge this picture Figure 3. Projecting side slopes.

Function 3: The ability to project side slopes of objects to various targets, which include other surfaces and elevations of interest. In Figure 3, the building is tied out such that it creates sideslopes around the building at a 3:1 slope until it hits daylight. Very minor editing was done to erase the tie-out on the sides where the retaining wall exists.

Command: pad

Pick the pad polyline:

Loading edges…

Loaded 2564 points and 7490 edges

Created 4927 triangles

Enter the fill outslope ratio <2.00>: 3

Enter the cut outslope ratio <3.00>:

Range of existing elevations along pad: 455.80 to 460.98

Enter the pad elevation <456.00>:

Calculate earthwork volumes [/No]? n

Adjust parameters and redesign pad [Yes/]? n

Trim existing contours inside pad perimeter [Yes/]n?

Function 4: The ability to offset 3D objects based on a variety of parameters. In this case, we want a 3' high retaining wall that is 1' wide and then comes back to natural ground. The side of the wall is almost--but not quite--vertical, hence the 0.05 offset value. Once the last pline is located correctly, another draping occurs to project the object back to existing ground.

Command: offset3d

Enter the offset method [Interval/Constant//Surface]: i

Vertical/: .05

Percent/Ratio/Vertical offset amount <0>: 3

Select side to offset: [User picks a side to indicate which way the offset should occur. This command is repeated to create the 1' offset with no elevation change, because the top of wall is flat.]

Select a polyline to offset (Enter to end): [terminates]

Command: OFFSET3D

Enter the offset method [/Constant/Variable/Surface]:

Vertical/Horizontal offset amount <0.100>: .9

Percent/Ratio/Vertical offset amount <3.000>: 0

Select a polyline to offset: [user picks the pline in question]

Select side to offset:

Select a polyline to offset (Enter to end):



Command: OFFSET3D

Enter the offset method [/Constant/Variable/Surface]:

Vertical/Horizontal offset amount <0.800>: .1

Percent/Ratio/Vertical offset amount <0.000>: 0

Select a polyline to offset: [user picks the pline in question]

Select side to offset:

Select a polyline to offset (Enter to end):

Command: 2dto3dpf

Loading edges…

Loaded 2564 points and 7490 edges

Created 4927 triangles

Select polylines to convert. [user picks the pline in question]

Select objects: 1 found

Select objects:

Use current polyline elevations as vertical offset from surface [Yes/]? n

Keep existing polylines [Yes/]? n

Set layer name for converted polylines [Yes/]? n

Converting polylines …

Elevated 1 polylines

Enlarge this picture Figure 4. Merging a surface.

Function 5: The ability to merge surfaces cleanly and predictably. As shown in Figure 4, a surface is created from the work done to this point and then it is merged into the existing ground surface and renamed as a merged surface. This function is performed by selecting the existing surface and merging the finished ground of the building and retaining wall into it. Most software packages offer this type of functionality as a standard command. Note the building foundation, the tie-out and the retaining wall shown in Figure 4.

Function 6: The ability to simplify surface data because many of the control boxes within the equipment have memory limitations. This is a comment that typically assists contractors with fitting more of the site onto their controllers to avoid continually downloading pieces of the project as they move to different parts of the site. Of course, this must be accomplished in such a way that the accuracies are not diminished.

In summary, these 3D layout functions can be performed with only meager input from the user. The result is the construction of an accurate model of the desired design intent. These functions are not hard to perform by any stretch of the imagination--and stretching a firm’s offerings to provide these 3D modeling services can lead to new revenue sources and improved relationships with contractors and developers.


Reference

1. Fauerbach, Shanon. “Special Report: Civil Engineering Technology, The state of practice,” CE News, November 2007.