MAGNET Modeler for Autodesk: Importing Civil 3D data

How to import Civil 3D data into MAGNET Modeler for Autodesk.

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MAGNET Modeler for Autodesk: Importing Civil 3D data

The Civil 3D plugin is used to import native Civil 3D data into a MAGNET Modeler model. This means that Civil 3D objects are recognized, and no additional conversion is required.

The plugin can be accessed via the Civil 3D icon in the MAGNET Modeler for Autodesk user interface. Double-click the icon to start the plugin.

Supported Civil 3D objects

Currently, the following items/Civil 3D objects are supported:

  • Civil 3D surfaces: TIN surfaces, corridor surfaces, and grading surfaces
  • Civil 3D pipe networks: both pipes and structures

This means that to visualize a corridor, corridor surfaces must be created in Civil 3D first. A corridor surface is then added automatically to the Civil 3D surface collection with the Prospector tab (toolspace) as a CORRIDOR TIN SURFACE and will be recognized by the plugin automatically.

How to use the Civil 3D plugin

You can add new Civil 3D objects by double-clicking the Civil 3D icon or by right-clicking it and selecting insert from the contextual menu.

The Civil 3D plugin dialog box is opened, and all supported Civil 3D objects from the current drawing will be listed.

Each Civil 3D object creates its own group.

Only objects that are marked as Selected will be brought into the MAGNET Modeler model.

Material and cut mode

You can select a material and cutting option for each group.

Cut mode has three options:

  • No cut
  • Cut
  • Weld

Cutting only affects how surfaces relate to one another.

If cut is selected for a surface, then this surface cuts holes to all other surfaces that appear before the active surface in the list. You can modify the order with the up and down arrows.

If weld is selected, all other surfaces are welded to this surface.

Checking the Locked box means the surface will not be cut or welded.

Rows can be moved by selecting a row and pressing the up or down arrows.

This dialog box also has a contextual sensitive menu. With it you can check or uncheck a whole column and set the same material or cutting option for multiple rows at once. This is done by setting a value for one row, selecting multiple rows, and from the context sensitive menu selecting Set same material or Set same cut mode.

The Simple manholes check box only affects Civil 3D pipe networks. With this box checked, only simple manholes (cylindrical) are shown in MAGNET Modeler.

Creating PDFs

When you select Create PDF, the program creates PDF documents from profiles. It also creates clickable links as a model attribute (Info).

If you have added Civil 3D objects to the MAGNET Modeler model builder definition, they are shown in the user interface.

You can edit a setting by double-clicking the item or right-clicking it and selecting settings. Items can be removed by pressing delete or selecting remove from the context menu.

Background on Civil 3D surfaces

A Civil 3D drawing can contain different types of surfaces. The two main types are (land) surfaces and corridor surfaces.

The land surfaces are surfaces like an existing ground, a parking lot, etc.

Surfaces are basic building blocks in AutoCAD Civil 3D, which are created from LandXML data, TIN (triangulated irregular network), and DEM (digital elevation model) files. They use points, point files, DEM data, existing AutoCAD objects, contours, breaklines, and boundaries.

Within the group of surfaces, multiple subtypes are possible:

  • TIN surfaces
  • GRID surfaces
  • TIN volume surfaces
  • GRID volume surfaces

Only TIN surfaces are currently supported in the Civil 3D plugin for MAGNET Modeler.

Corridor surfaces are created from a Civil 3D corridor (a 3D design model for something like a road, a railway model, or a pipe network trench).

These corridor surfaces are not created automatically when a corridor is created. The creation of these surfaces is a semi-automated task. These corridor surfaces are an output of a corridor model, which are created manually by extracting data from a set of link codes and corridor feature lines. The surface will remain dynamically linked to the corridor, and any changes to the corridor definition are reflected in the surface definitions within the Prospector tab. However, you can also create a detached surface from a corridor.

Best practices for creating corridor surfaces

Only one material can be applied per Civil 3D surface. This means that for a corridor model, a surface for each different material must be defined. Lanes, curbs, medians, shoulders, ditches, and slopes should all have their own material. This means each needs to be defined as a separate surface. This can be done rather quickly if you have a good understanding on how a corridor model is built.

A corridor model is built out of 3 components: a horizontal alignment, a profile (vertical profile geometry), and an assembly (typical design cross section, road description).

The assembly is built from subassemblies. Subassemblies (structural forming blocks) are elements that compose the geometry and substructure of the corridor model. A subassembly can be a lane, a curb, the pedestrian sidewalk, a shoulder, a ditch, etc.

The geometry of a subassembly is defined around points, links, and/or shapes. Each point, link, or shape element has one or more codes attached.

The defined codes for each element are explained in the Civil 3D subassembly help.

The link L1 has more than 1 code attached. The most upper link (L1) in this subassembly has the code "Top" but also another code “Pave” attached.

These codes can be used when defining corridor surfaces. For example, if one is interested in creating a surface that combines all codes "Top" from the different subassemblies, one could visualize the top layer of the designed model. Similarly, when combining all codes "Datum," one could build the surface needed by the contractor to define the bottom of the road model.

However, to be able to distinguish between the different materials, we could use the other codes attached to the link to be able to distinguish between pavement asphalt, concrete for the curbs, and tiles for the pedestrian sidewalk.

The "Top" code allows you to easily create a surface of the complete model and is by default already attached to all subassemblies. The other codes allow you to create surfaces for each different material.

This is what needs to be used (the codes that define the material) if a corridor model needs to be visualized with MAGNET Explorer.

In the example below, there are 4 different codes: "Pave," "Curb," "Shoulder," and "Slope."

Once the codes to be used are known, the surfaces can be defined.

Select the corridor in the drawing, and navigate to Modify Corridor > Corridor Surfaces.

In the dialog box, click Create a corridor surface (first button).

A new surface is created and listed in the table. Now, the link code(s) to build the surface from need to be added. Therefore, the code must be selected from the Specify code drop-down menu. Once this is done, click the Add surface item button to add the code to the surface.

Once the code is added to the surface, it is a good habit to select the Add as Breakline check box and choose Top Links in the Overhang Correction column. This usually creates more accurate surfaces.

It is also a good habit to rename the corridor surface so that it is more informative than the automatically generated name. It will help you in MAGNET Modeler when you have more complex models built around multiple corridors.

It is recommended to use the corridor name and the link code in the surface name, for example: 

  • [RoadModelName]_Pave 

This makes it easy to assign MAGNET materials later on.

Now that this dynamic surface has been created (it will change automatically when you change the corridor), there is often some manual cleanup actions that must be done. Mostly this will have to do with cleaning up the boundary of each surface. Correct automatic boundary creation is often difficult.

If the subassembly has a constant width, you can use the build options from the surface properties dialog box for this (corridor) surface and define a maximum triangle length.

If there is no constant width for the assembly and/or a lot of curves in the main alignment, the user will need to manually delete the erroneous triangles. This can be done by using the surface edit operations.

Both actions can be started by selecting the surface in the drawing and choosing the appropriate function in the ribbon.

Best practices for working with large and complex Civil 3D project drawings

To optimize working with larger Civil 3D datasets, Civil 3D has the ability to define data shortcuts. In short, these are references to Civil 3D objects that are stored in other drawings, similar to XREF behavior in standard AutoCAD.

This means that you can create your surfaces, corridor, and pipe networks in individual drawings and then create a reference to them in the visualization drawing. This way, only the result of the object is stored in the active drawing, while the definition of the object is stored in another drawing.

The Civil 3D plugin supports this way of working.

If you want to know how to define and work with data shortcuts, please refer to the help in Civil 3D.