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Welcome to the second part in our series on creating custom components. In this particular article we are going to look at the two primary component types to be found within Revit, the differences between them and how and when each would be used.

As stated above there are two primary types of components within Revit. Note the word “types”. There are literally thousands of different components, but only two main “types”. So let’s have a look at these.

3D (model) components

These components have 3D geometry are often termed “model components”- because they appear in your Revit model, in all their 3D glory! Examples of model components are doors, windows, furniture, etc.

These components are either “Hosted” or “Free Standing”. We will be covering this in detail in Part 7 “Independent versus Hosted Components”- but just to say here that Hosted Components require a Host element to relate to. For example Doors can ONLY be placed in (ie hosted by) walls. Once “hosted” the hosted component maintains it’s relationship with it’s Host. Ie You move the wall and the door moves with it- which is quite useful.

3D components can have 2D symbolic representations appear in specific views “instead” of the 3D geometry. For example: If you take a look at our door (in the image above) what you are seeing is the “actual” 3D geometry that makes up the model of the door. But if we switch to a plan view of the door we see….

You have probably ascertained that we are “not” simply looking down on the model geometry. What we are seeing is a completely different representation of the door- displayed in place of the model geometry. The displaying of 2D view-specific representations in lieu of the actual geometry is an important and well-used concept within Revit. Furthermore, we can change the 2D representation depending on the Detail Level we choose for each view. Notice how the image below is different from the one above…..

The main concept that I want you to understand from this is that there are TWO types of representation- there is the actual model geometry and there are 2D symbolic representations. And the two can be completely different. Take an electrical socket for instance. The 3D geometry looks like this….

But in plan we see the following….

Electrical Engineers and designers will know that this “represents” an electrical socket, but in reality it has no inherent similarity to the 3D model geometry. And that is the beauty of how Revit handles custom 3D components. If you wish, you can just define the 3D model geometry and have it appear as such in ANY view- including plan views. OR you can define a number of independent 2D symbolic representations and have Revit display these INSTEAD of the model in any view that you SPECIFY.

Note: That although the 2D symbolic part of the component is not strictly part of the model geometry- it does appear in any model view, in lieu of the 3D geometry. But only when it has been defined (ie you have to draw it out) and the appropriate views specified.

Detail (2D) Components

The other main type of component is the Detail Component. These have NO model geometry. They are purely 2D representations. Just like Detail Lines and Symbols, they are “View Specific”. That is, they ONLY appear on the View in which you place them. They are NOT part of the model and will NOT appear in 3D views.

Here’s an example…

Next to our electrical socket I have placed a Detail Component- in this case a Universal Beam. But if I switch to a 3D view….

There is no sign of a column anywhere. Even the 2D representation of the column that we saw in the plan view is not shown- and there is no way that it can be shown- it’s made of 2D lines. Just like the 2D symbolic representation present in the 3D components, Detail Components are “actual size” and scale accordingly with the model elements around them. For example 

If we measure our beam, we see that it is indeed “actual size” and will remain so, no matter what scale we set the view at.

Symbols

Not strictly Components, but worth briefly mentioning here nonetheless. Symbols share SOME similarities with Detail Components but have one MAJOR difference.

As with Detail Components, Symbols are View-Specific. They are NOT part of the model and consequently do NOT appear in 3D. However, UNLIKE Detail Components, Symbols are sized according to their printed dimensions. If you go right back to our electrical socket example (see 3D Components), the 2D representation is actually created using a “Symbol”. So no matter what scale we view our plan at, the symbol representing the socket will be drawn / printed at the SAME size.

Let’s summarise…..

We have seen that there are 2 main Component types in Revit. 3D Components and 2D Components.

• The 3D components can either be hosted or “free-standing”

• 3D components can consist of pure 3D model geometry OR have 2D symbolic representation (that are View-Specific) included in their definition, They can even include Symbols that represent the component, in plan views.

• Detail Components are 2D representations of building / model elements. They measure and scale as if they are part of the model, but remain View-Specific.

• Symbols have some common traits from each of the above and also some major differences.

3D Components are arguably the most important and interesting aspect of Revit. In the rest of this series of articles we will look in detail at exactly how they are created.

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Proceed to Part 3