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Cut with Voids When Loaded

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If you've started to experiment with making your own custom components using Revit's Family Editor, you may have seen that the Model-based (as opposed to the Annotation-based) Family Template files contain a parameter called "Cut with Voids When Loaded"
 
 
In this short article we are going to take a look at exactly what this parameter does; and when it would be appropriate to utilise it. 
 
First of all I create a section of floor in the Project Environment. It really doesn't  matter what Floor Type we use, I just want to have something in the Project that will be cut by our Family, once we load it and place an instance. So here is our floor....
 
 
And that's all we need to do in the Project Environment, for now. So it's now time to switch to the Family Editor and create a simple family that will contain a void, that cuts our floor when loaded. For this example, I am going to use the "Metric Generic Model" template....
 
 
I am going to keep this family really simple- because it's just the concept that I want to focus on. My Family is only going to have 2 elements in it- a solid extrusion (going upwards above the Reference Plane) and a void extrusion (going downwards, below the Reference Plane). It is this void that will cut through the floor element, once we use the Family in the Project Environment. So here is the solid extrusion....
 
 
And no I am going to create the void extrusion next to it......
 
 
Notice how I have made the top face of the void extrusion slightly higher (50mm) than the Reference Level (which is the same height as the base of the solid extrusion). This is to ensure that the void cuts "entirely" through the Floor element when loaded. I don't want the top face of the void to be coincident with the upper surface of the floor element- better to be on the safe side!
 
Now the only thing left to do in the Family Editor is to ensure that the void we have just created actually cuts through solids when it is used in the Project Environment. To do this we simply check the "Cut with Voids When Loaded" parameter in the Properties panel (Properties for the entire model, that is).....
 
 
I can now "Save" my Family and then "Load" it into the Project Environment, where it will be ready to use. In the following image you will see that I have now loaded the family into the Project Environment and placed an instance of it into the (very sparse!) model......
 
 
But STOP! What's happened? Where is the cut in the floor, made by the void? Panic Not! The cutting of the element by the void is not automatic. You need to use the "Cut Geometry" tool....
 
 
 
Simply select the "Cut Geometry" tool- then select the Floor element (first) and then select the Family (second).
 
 
That's more like it! Please note that this cutting of the geometry was only possible because we checked the parameter "Cut with Void When Loaded". With a little imagination I am sure that you will come up with many situations in which this parameter is very useful. A typical example is where you have created a custom family that sits on a worktop (ie a sink) but needs to also penetrate through it. This will save you having to "manually" form the aperture in your work to by editing the in-place extrusion. I'm sure you'll find many other situations in which to use this.
 
And finally before we end. You must note that NOT all Revit Categories are capable of being cut by voids. The only ones that can are: Ceilings, Floors, Generic Models, Roofs, Structural Columns, Structural Foundations, Structural Framing and Walls.

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