The Industry Foundation Classes IFC specification is a neutral data format to describe, exchange and share information typically used within the building and facility management industry sector. IFC is the international standard for openBIM
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Exports to the IFC format can be done in an AutoCAD version that supports conversion (usually AutoCAD Architecture). This article is a step-by-step guide that will cover how the export is done. First, the model must be generated in an empty drawing. Create one under the category 3D in the project browser, as shown below.

Figure 1: New 3D drawing

Open the empty drawing and generate the elements that will be included in the export by using the generate plan command. Configure your selection of elements and be sure to select the AutoCAD solid (IFC) option found under setup. This allows export to the IFC format.

Figure 2: Generate the elements as IFC-compatible solids 

Select Cast-in Materials

Next, a question will show up "Generate cast-in materials Yes/No/Selection"

Yes will include all of them, No will exclude all of them and selection lets the user decide which cast-in materials that should be included. 

The dialog that will show up if Selection is chosen is shown below. Here the user can check/uncheck cast-in materials to be included/excluded when the elements are generated. To help with the selection there is the possibility to filter cast-in materials by group and/or a free text search for the cast-in material name and description.

Note, if the user makes a selection, that selection is stored in the drawing and will be used the next time the user answers "Yes" or "Selection".

Note, all cast-in materials are drawn together with the element, so this can't be used to add/remove any cast-in material from elements already drawn on the drawing.

Figure 3: Select Cast-in Materials

Chose what information about the elements to include in the export. This is done through the "add property set" command found under the "base" tab in AutoCAD Architecture.

Figure 4: Add property set...

Select the options that are interesting to include, and then click ok to close the dialog. It is compelled to actually press "ok" to include entries in the export, even if you do not make any changes to the list.

Figure 5: Select properties to include in the property set

Make the export from the AutoCAD Architecture file menu as shown in the image below. 

Figure 6: AutoCAD export to IFC

Enter a project number and change any other information. Then proceed by pressing export.

Figure 7: AutoCAD export to IFC dialog

Element color

Note: When an IFC-export has been made, the colors that are represented in an IFC-viewer are not connected to this variable or IMPACT as the IFC-export is a pure Autodesk and Bricsys export.

The variable presented below is only affecting elements that are opened in either AutoCAD or BricsCAD.

The elements in the export can be colored in two different ways, both of which depend on how the variable SOLIDCOLORBYMATERIAL is configured. Either, the elements get the color based on AutoCAD's layer 0, which by default is black. Or, the elements will be colored based on their material color. Materials are configured in Standard Admin with an exact color (RGB value).

With the variable value set to 0 (turned off) the model will inherit the color of layer 0 - black.

Figure 8: IFC model colored by layer 0

With the variable value set to 1 (turned on), the elements/components will inherit the color of its material. In the example below the walls have a grey color from the concrete and the CIMs have a slightly darker gray which makes them visible when the model is viewed as somewhat transparent.  

Figure 9: IFC model colored by material color (true color)

Access IMPACT data

In this example, I've opened up an IFC model exported from IMPACT in Solibri Model Viewer. I've included some data in the export according to one of the chapters above and it appears under the IMPACT tabs, as shown in the image below. There is the information I chose to include like geometry, weight, and element mark.

Figure 10: Accessible IMPACT data

Note: 
IFC export is not our own function, we are utilizing existing functions in the designing program and the IFC export can vary from program to program. You should also be aware that different IFC viewers also can give a different outcome of the same model.

We use the IFC viewers BIMvision and Solibi as a reference to see if the models are displayed correctly. This means that if the IFC model is shown correctly in one of the two viewers we consider the IFC export as correct.

Here you can download a free version of these IFC viewers 

BIMvision
Solibri