Adding and Removing Surface Boundaries and Other Data To Takeoff Surfaces

This one comes up a lot. When we do a Takeoff, we categorize layers as Design or Original or Other etc. and those categories are used to group 3D objects that are on those layers so that we can build surface models for the Takeoff process. Most users believe that the only way to create a Takeoff surface is to place the required objects on layers that are categorized as Design or Original, but that is not the case.

You can Add / Remove surface members to / from a Takeoff Surface and you can also Add / Remove Surface Boundaries to / from a Takeoff surface, just like you can do in other surface models and corridor surface models.

When we create a Takeoff Surface we look in what TBC calls containers of data. Those Takeoff Surface containers are built from the 3D objects that reside on the layers that you categorized, but they are supplemented by other objects that you add / remove from the Takeoff Surface.

In the example in the video, the user created a surface model for a Road Project that they created from flipped CAD Cross Sections. At the North end of the project there is a Bridge that they did not want computed in the surface TIN. so they created two 2D boundary lines on a layer and then categorized the layer as Design. When they built the Takeoff Surfaces, the boundaries did not act as boundaries as they had hoped (hence the call and the help video below).

The reason that they did not work as Boundaries as hoped are as follows

  1. The Categorize function creates the object data for the Takeoff Surface, but it only selects and uses 3D data
  2. The Categorize function provides no means of saying that the lines on a layer will act as Takeoff Surface Boundaries and so even if they were 3D they would still only be used as breaklines and not as boundaries.

The answer here is to not categorize this layer at all, and just use the Add / Remove Surface Boundaries function, and add the two boundaries to the Finished surface (A Takeoff Surface). The surface will rebuild and the boundary is applied as desired, and the model is good for the Takeoff Calculations to be processed.

Thanks Frank for raising the question - all great learning points.

Note that you can use Add / Remove Surface Members to add Point Clouds or objects on other layers not categorized in the Takeoff process to surfaces computed by the Takeoff process.