Creating a Custom Terrain

When should you use this?

This feature manipulates the topography of the map to improve the accuracy of the terrain.

When creating a project in cmBuilder, terrain is automatically generated for topographic maps. This is done using satellite data, so there may be inaccuracies due to buildings or trees. Also, the accuracy of satellite data may not be enough for what you need.

This feature allows you to update the topography of your map, provided you have some information to give it. The most common sources of topography data of your project are:

  • Survey data (points with elevations)
  • Topographic map data (elevation contour lines)
  • Drone scan data
  • landscape geometry from your imported models

If you have any of these, and are unsatisfied with how your current terrain looks in cmBuilder, then this is the feature for you!

Who can use this?

This is available to all users who can edit a scenario, provided they have the experimental feature enabled.

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Steps

  • Open the Custom Terrain Feature
    • Go to Project Setup, followed by Custom Terrain

  • Create a new terrain using the Create Terrain button in the top left
    • If you have an Imported Model or Imported Mesh, choose Create Terrain (Mesh)
    • If you have a drawing to reference or a point cloud, choose Create Terrain (Points)

Create Terrain (Mesh)

for Create Terrain (Mesh), the terrain will drape to an Imported Mesh that you upload and position within the scene.

  • Select an Imported Mesh to use for your terrain (or upload a new one) and press Load

  • You can now choose your blending method and distance
    • This determines how the surface of the mesh tapers into the remaining part of the map
    • Blending method is the shape of the drape surrounding the mesh
    • Smoothing distance is how far the drape reaches beyond the mesh before it touches the map
  • Once you have chosen your blending settings, you can Generate Preview to see the result
  • Choose if you want to set this as your initial terrain with the checkbox
  • Press Save

Create Terrain (Points)

For Create Terrain (Points), you place control points around your map, and choose an algorithm that will create a new surface for the map that passes through your points. See the Tips & Tricks section further down in the article, for advice on how to position your points. There are two main ways to add points.

  • Adding points manually
    • You can click on the map to place control points - by default they will be on the map surface when added
    • Once the first point is placed, additional options will become available, including:
      • You can toggle on Use last selected point's elevation to maintain the same height while adding new points, instead of on the map surface

  • Import point data
    • Download the template to see the format that is used for importing point data
    • You can import a point-cloud from a CSV file into cmBuilder
      • This can be generated from Excel or similar programs
      • These can be done in coordinates relative to your cmBuilder, or using UTM (a geolocation coordinate system in meters)

  • Edit your points if needed
    • You can choose to Move your existing points in the scene if you want
    • You can also edit point values or delete points from the table
    • Alternatively, you can export your list to a CSV, edit them in Excel, and re-import them into the Custom Terrain
  • Choose your point-blending mode
    • Inverse Distance Weighting
      • A very fast algorithm, but often makes plateaus between points
      • Can be useful for first testing out your terrain, since it will preview faster
      • Good for cases where you have many flat areas in your terrain
      • Good for cases where you have a grid of points
      • Not good for points that are randomly distributed
      • A weighting of 5 will make things more plateau-like, whereas a weighting of 1 will make things steeper at the points
      • Note - it is advised to place a point in each corner of your map for this algorithm, as it will create steep walls in a circle around your set of points
    • Kriging
        • A slower, but much smoother algorithm
        • Kriging Groups splits the work into a grid, which makes it work much faster, but may create a grid of slight valleys in your terrain

Inverse Distance Weighting - 1, 3, 5

Kriging

  • Click Generate Preview to see changes. Note that this may take a while for large numbers of points, and is slower for the Kriging algorithms
  • Choose if you want to set this as your initial terrain with the checkbox
  • Click Confirm to implement change

 

Finalizing your Terrain

  • You will now see the Custom Terrain overview sidesheet again
    • Note that you can choose which Terrain you want to show up in your scenario from here
    • Currently, only one Terrain is usable per scenario

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Tips & Tricks

  • Editing lots of points
    • If you are having trouble editing lots of points using the table on the right, you can export your list to a CSV, edit them in Excel, and re-import them into the Custom Terrain. This lets you use all the tools and flexibility that Excel has to offer.
  • Amount of points to use
    • Due to the geometry of the map in cmBuilder and how the algorithms are applied, it is recommended to not put points closer together than 5m, as it will not increase accuracy, and will slow things down. If points are too close, it may also cause the algorithm to fail, or cause silly-looking results
  • Working with a contour map
    • If you are starting with a contour map, you will want to use the point mode, with the Used Last Elevation applied. Then place points every 10-30m (30-100ft) around an elevation line. It is recommended to not do every elevation line, unless the terrain is mostly flat. However, each application is a little different, and YMMV (your mileage may vary).

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