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Welcome to part 12 of this 17 part series on creating your own custom model components using the Family Editor. If you have just stumbled across this article without reading the previous parts of the series, you may want to start here.

In part 5 we touched on the use of solid extrusions in forming your 3D geometry. In this article we’re going to go over this again and in a little more detail. 

Solid extrusions are at the very heart of the process of creating 3D geometry. I would go as far as to say that in creating your own custom 3D model components, you will be forming solid extrusions over 90 per cent of the time. So it’s really worth getting to grips with how this important tool works.

Before we get into a specific example, let’s go over some of the fundamental key concepts of solid extrusions.

• Extrusions consist of two elements: A Profile and a Path.

• The Profile is the outline of the shape that you wish to extrude.

• The Profile will always be as 90 degrees to the direction of the path.

• The Path is always a straight line and is perpendicular to the plane in which the Profile was drawn in.

• The Profile must include at least ONE closed loop.

So let’s look at both the Profile and the Path in more detail….

Profiles

Profiles are drawn in Sketch Mode using all the standard drawing tools. You can use lines, arcs, rectangles, etc. You can use the Offset, Trim, Split, Align commands, etc. Here is a view of the Options Bar when in Sketch Mode, ready to draw a profile…

Here is a Profile that I‘ve sketched out as an example- just to show you the complexity of extrusion that you can form…

Notice that the Sketch is a CLOSED Loop and at NO point along it’s length does it cross it’s own path.

An important thing to note is that if we add other closed loops INSIDE of this primary loop, we will form a profile that will go on to form voids in the extrusion. Let’s add some voids to our profile….

Note the 3 smaller closed loops that I’ve draw within the main loop. Let’s see what type of extrusion this forms…..

I’m not sure what you would use this for, but you get the idea! So now you know how to draw your profile, let’s take a look at Paths.

Paths

Profiles are no good without a path. If you don’t have a path, you’ll just end up with your 2D profile! As we have said above, Paths are always perpendicular to the plane in which the profile was drawn in. Unless you tell Revit otherwise it will start the path exactly on the reference plane that the Profile was sketched in. ie the Path will have a Start Point of 0. That is it is 0 units away from the plane of the Profile.

We can see this by clicking on “Extrusion Properties” and taking a look at the Control Panel…

The default length of the Path is 250mm (NOTE: your units will vary depending on the standard units of your country). You can see the default “250” in the “Extrusion End” box, in the image above. So again, 250 refers to the distance away from the plane of the Profile. You will notice that the Work Plane to which these figures refer, is shown greyed out in the same dialogue box.

Please Note: You are not restricted to absolute numerical values for the Start and End of your Extrusion. If you look carefully at the end of each line (for Extrusion Start and Extrusion End) you will notice a little grey square….

If you click on either of these you will see that you have the opportunity to add a Parameter to control this value.

This is VERY powerful as you can make you Extrusions really flexible- ie they can be modified in real time by end users, just by changing their Parameters in the Element Properties control panel. If you’re going to do this, just make sure you think about whether you need Instance or Type Parameters in these situations.

Note that you can have negative values for Extrusion Start and Extrusion End. These are just distances away from the “other” side of the Work Plane that the Profile was drawn on. For example, if you set the Extrusion Start at -100 and the Extrusion End at 100, then the Path has a length of 200.

Proceed to Part 2 of this article