Working With IFC Files

What Are IFC files?

IFC files are a useful medium to transfer 3d Design data between BIM and other software such as n4ce.  They contain not only 3d geometry but can also contain a vast array of attribute information as well.  So whereas DXF files can also contain 3d faces, IFC files also allow for almost any information imaginable to be included with the design data.

Getting Started.

To start the import process, simply drag and drop an IFC file from any file explorer into the 3d Viewer.  Then click on any element in the 3d view and the explorer will expand to locate that object in the tree view.

IFC data is nested, so a branch can contain a single object, or it can contain multiple objects or multiple sub nodes.  It all depends on how the data is arranged.  To visually turn something off, just untick its tree node.  Then all the geometry below it will be hidden. So to turn off all data pertaining to the roof of a building, for example, you just need to find the parent node for all the roof data.  By clicking on any roof entity in the 3d view the tree view will expand to show that element.  Just track up till you can see the node that contains all the roof elements, and untick it.

Using the IFC Explorer.

The explorer is split into three basic sections.  The Tree on the Left, the Actions in the middle and the Properties on the right.  The tree as already discussed lets the various nodes of the IFC be explored and investigated.

In the middle, the Actions section allows you to drill down and find just what you are after.  Without needing to manually hunt for the data in the tree view.  The following are a few situations that demonstrate how to use the searching functionality to home in on just what is needed.

• Scenario 1: Locate and make visible JUST the walls.

  Click on one wall and note its TYPE in the top right of the explorer. 
  
  Then from the Element box in the middle of the explorer, select that Element type and then click on "Add to Selection".  All objects of that type will now be selected.  Now click on the "Invert Selection" button below that.  As a result, all the data that is NOT needed is now selected, so just uncheck the Enabled box at the top, and they will all disappear leaving just the walls.
  
  
  

• Scenario 2: Locate and make visible JUST the GROUND FLOOR EXTERNAL walls.

  The previous situation located the necessary elements by their type.  This time we are going to use the fact that the IFC file contains useful attributes. 
  
  In this case, we will be looking for External Walls, so we can use the "Find Similar" button to find similar walls to any we pre-select. So by holding shift and clicking on two ground floor external walls, then clicking "Find Similar", only walls that match that criteria are selected.
  
  So now all we need to do is invert the selection, and uncheck the Enabled button.  To leave just what we need behind.
  
  
  

• Scenario 3: Locate JUST the major Steel Members.

  Here we have been provided detailed structural steel drawings and need to conduct an as-built survey. However, the IFC also contains every nut, bolt, flange and plate that is also part of the build.  For our purposes, we only want to work with the major columns and beams.  
  
  So to do that we will again turn to the Properties.  In this example, there is a "Length" property associated with each element.
  
  It can be argued that the major elements will be over a meter long.  So what we can do is filter by this attribute and enter it into the Property Evaluation box, and setup the inequality thus... I.e. Select all elements with a length less than 1m.  Once they are selected then they can be turned off as before.
  

Extracting Triangles

Having filtered every element out that is not needed so that the 3d view contains only those elements that are required, if needed, those triangles can be extracted and pushed into a normal n4ce Model.  From there they can be further manipulated or exported to various systems depending on the use case.  To transfer the faces in the 3d view to a model click the "Commit Triangles" button. If this button is not active, then no elements are selected. You will then be prompted to enter a name for the new model that will be created in order to hold the necessary triangles.

Extracting Line Work.

Instead of extracting triangles, linework can also be extracted from IFC data.  The process is a little different to the above though as usually only 3d faces are available in IFC files.  To get any linework, we need to use n4ce to make it for us.

Depending on your version of n4ce there are two ways to extract the linework.

• Designer: With the Designer version simply place a section through the data at the desired location and when it's in the correct place, click the button in the IFC Explorer labelled "Lines From Section". The tool settings will appear in the top right of the screen.  Here you can set the code of the points that will be generated and if needed click "Live Update" so that you can move the plane into a better place or allow multiple slices to be taken.  When "Digitise Lines" is clicked in the tool settings, the linework from the section will be added to the current model, using the current code.

• Lite & Pro: Lite and Pro do not have the Section tools in the 3d view.  However, if the triangles are committed to a model first, using the process above.  Then view the model, and go to the Adjacencies option under the DTM Menu\Tab.  This ensures that each triangle now knows which triangle is next to it.  Normally this info is added during a DTM calculation.  But as these triangles came from a different source, they will need their adjacencies reset first.  Having done that, select the DTM Boundary Import option and provide a suitable code.  n4ce will then generate a string of points around the external edges of the triangles in the model.