Incorporating Dynamic Blocks to Generate More Accurate Civil 3D Models

Figure 1: Exaggerated fence layout

In order for us to fully embrace the 3D environment, we need to completely change our way of thinking and designing. We continue to rely on custom linetypes to represent a lot of our site features being displaying on our plans.

By creating 3D elements in AutoCAD and converting to dynamic blocks, we can begin to remove at least some of the 2D linetype representations we so heavily relied on in the past to display various site components. The following example will go over the process of creating a dynamic block to replace a simple Civil Site 2D linetype.

Figure 2 is a picture of a typical chain-link fence in 2D view.

Figure 2: Typical 2D chain-link fence linetype

With the use of the 3D Solid Modeling built into AutoCAD (and available in C3D by switching your workspace to 3D Modeling), we can create an accurate 3D representation of what this fence should really look like. You would want to start off with a standard fence based on a detail from your local municipality. Keep in mind this block can be modified later on to accommodate any special requirements needed for different clients/owners or site constraints. Once completed, your new appearance will look like this in 2D and Isometric views:

Figure 3: New 3D chain-link fence linetype shows pole and foundation

Figure 4: Isometric view of new chain-link fence

Once you have your 3D representation set up the way you want it to look, we would then convert it to a block. In Block editor, we can add Parameters to define distances, points, visibility settings, etc. to better define how your block is, and should be, represented in 3D views. We can further manipulate it to apply Actions to each of the Parameters to define how you want the block to act as you lay out your site features in your Civil 3D models. In this instance, I have applied stretches to a few of my distances to give me the ability to extend poles and fencing along alignments as necessary. I have also added an array to my horizontal distance so that as I stretch my chain-link fence block, the poles will copy in an array along the alignment as well. In this situation, I have set my array to 10’ intervals/spacing.

Figure 5: Chain-link fence definition in block editor – 2D wireframe view style

Finally, if you switch your view display setting to realistic, you can apply the chain-link fence appearance to your block through the Rendering Materials Browser. You may also need to adjust the material mapping interval such that it looks like a true 3D chain-link fence with correct mesh spacing.

Figure 6: Chain-link fence definition in block editor – realistic view style

After you’ve set all your parameters and actions, save and close out of block editor. If you switch to your isometric view and select your new block, you will also see grips in places where you have defined your actions.

Figure 7: View of block as inserted into your working model

Figure 8: View after using one of the grips to stretch the chain-link fence block in your working model

Your block is now ready to be incorporated into your Civil 3D model.

Figure 9: Realistic view of chain-link fence

Figure 10: Realistic view of chain-link fence

Figure 11: Realistic view of chain-link fence

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