The family creation process - Revit Tutorial

- [Narrator] In this chapter, I want to begin looking at parametric, or what we sometimes refer to as flexible families. So, parametric or flexible families are families that have built-in behaviors or constraints or rules or other characteristics that we want to be able to control in a flexible way, thus the name. When you're contemplating creating a flexible family, this may be a family that has different sizes, or it might have different kinds of visibility that are turned on and off under various circumstances, or it could contain both of those kinds of behaviors, or several more. When you're contemplating creating such a family, you want to approach building it very carefully. So, let me outline for you some of the basic steps that are involved in creating a parametric family. And the first thing is really just deciding what you need and planning it out carefully. So, this could be just jotting down some notes on a notepad, it could be doing some sketches, maybe detailing out which parts of the family need to be flexible, which parts can remain static or fixed. Just kind of having a plan of attack so that when you start working, you're not just guessing, you're actually building it with some strategy in mind. The first thing you'll have to do when you start this new family, is actually choose a template. Now, we've seen some examples of this previously, already, here in the course. When we were creating annotation families, it was pretty simple because the only real question that the annotation templates were determining is what category the tag or other piece of annotation was. But, when you're working with model components, which is what we're going to be shifting over to now, we're going to be creating parametric model elements, things you actually place in your model that would represent physical, real-life stuff, there's going to be a couple things that you'll be determining from the family template that you choose. Now, you're still going to be choosing the category, but a really important aspect of what you'll be choosing is the hosting behavior. So, does this family require a host? So, we have all different types of hosting behaviors. We have wall-based families, and ceiling-based families, and roof-based families. So, if you want one of those behaviors, if you want to require the family you're creating to be associated with one of those types of elements, then you choose a hosted template. If you don't want that behavior, then you chose a non-hosted template. If you're not sure, it's always safer to choose a non-hosted template because unlike most things in Revit, you can't change your mind on this decision later. So, once you choose your hosting behavior, it's permanently a part of that family. So, choose carefully. And if you're not sure if you need a hosting behavior, it's a little bit safer to create a free-standing or non-hosting family. Now, once you're in that family, one of the first things you do, is set up the overall structure of that family. Maybe define the extents, define the limits, some of the overall behaviors. And we do this by laying down reference planes. Now, we've already discussed references planes a little bit in some of the previous videos, but they will be an important first step in almost any parametric model family that you create. Once you've established those reference planes, you want to next establish how they're going to behave. And we have two essential ways that we do this in family editor, we either apply constraints to those reference planes, or parameters. So, think of a constraint as a rule that's build in to the family, that the end-user can't change in any way. And think of a parameter as a flexible rule that the end-user can modify. So, if you wanted something to always stay centered, that would be an example of a constraint. But if you wanted the length of some dimension to be flexible, and the user could type in different values for that length, that would be an example of a parameter. And we'll certainly look at both of these. After all of that setup, you're ready to build geometry. Now, if you watched the previous chapter, we jumped right in and started building a lot of geometry. And you may be tempted to do that when you build a model family. But, if you don't carefully plan things out and establish that armature, that form-work, those constraints and rules first, then building your geometry can actually get in the way and it won't behave as expected, and it can cause a lot of errors and problems. So, if you carefully approach it in the way that I'm outlining here, you usually get much more satisfying results and avoid a lot of unnecessary frustration. So, finally, after you've built all of that, it's important to test your family. Now, we typically call this flexing the model, in Revit terminology, so when we say you want to flex your family, what we're simply saying is put it to the test. We want to try out all of those parametric relationships that we've established, flex all those parameters, and make sure that the family doesn't break, or that if it breaks, it's breaking within limits that we can live with, and that we can easily correct if necessary. So, you want to flex early, and you want to flex often, and that's the best way to tell that everything is working correctly. So, what are we actually going to build, here, over the next several videos? Well, I was trying to think of a good example, and I was walking through our recording facility, here, and I noticed this small table. And I thought, well, that's a good candidate. It's got a lot of really interesting features, but it's also very simple. So we can do it fairly quickly and easily. And then, I was in my hotel room, and there was another table that was almost exactly the same as the one that I saw in our break room. And I thought well, this table is speaking to me, so a cantilever side table, it is. So, over the next few videos, we're going to begin approaching the creation of this cantilever side table, and we're going to make it parametric so that it can flex between a few different sizes.