Monday, July 2, 2012

Creating Walls That Follow Site Topography Contours in Revit

Using the intersection method to Create Walls That Follow Site Topography Contours

I just got back from RTC USA/NA where I taught 3 classes. The first one was on Adaptive components, the second one was on Game engines, and the third was on modeling complex geometry. I got the most comments and questions from this third class that described the intersection method and how to use it on site topography elements. I was very surprised when the master of all Revit tech support, Harlan Brumm from AUTODESK, commented that he did not know how to perform this task until he sat through my class.... Wow! I was honored to  hear that. Therefore, I felt it was important enough now to post the method on my blog page since not everyone was able to see me demonstrate it  at RTC USA 2012. 
Below describes the method on how to use the intersection method on walls so that they will follow the contours of site topography elements. If you are unfamiliar with the intersection method, I created it in order to allow Revit elements to follow the shapes of other surface elements. More information could be found in a article I wrote for AUGI World. September 2011.

This uses a  modified version of the intersection method to create a planar wall in Revit whose bottom follows the contours of a site topography element as shown in the Figure below. There are many ways to do this; however I found that this method below is the fastest way to create a wall that follows the contours without leaving the Revit program. First I have to state that the site topography modelling tools in Revit are “clunky” compared to other Revit modelling tools. If anyone has worked with site topography in knows that they are not very user friendly in regards to interacting with other elements. With the shortfalls of site topography in mind, take the following steps below to create a wall whose profile will follow the site topography contours.

Even though a wall’s profile is used in this example, this principle could be applied to a number of other elements including, curbs, pipes, etc..

  1. Add a building pad where the edge is at the centerline of wall shown in the Figure below. Make sure that the building pad is lower in elevation than the site topography.
    1. Note that no elements will “join” with the site topography so a modified “intersection” method will have to be used.
    2. Note that a building pad will “cut” a site topography element and therefore a building pad will be used as the “sacrificial” element.
    3. Notice that a new site topography element that just contains the boundary of the cut made from the building pad is created. It is this phenomenon that we will take advantage of.
  2. Simply select the “new topography” element that contains the boundary and export it as a Dwg and save as a new name.
  3. Add an in-place mass and insert the newly exported Dwg as origin to origin level 1 orient to view
    1. This will place the new site topography element as a dwg and will allow its edge to be “pickable”.
  4. Add a wall by picking the edge of original building pad and extend the top limits to any desired height. In the case shown in Figure 15, it is shown stepped.
  5. Edit the wall profile and pick the edge of the inserted Dwg/in place mass and trim the edges as shown in Figure below.

Site Wall following contours of site topography

Cut in site topography and new site topography element

Wall profile and pickable lines