Introduction to Maya 2012

In this lesson, we'll take a look at the process of parenting and grouping objects within Maya. So for this lesson, I'm going to open up the scene file called parenting underscore grouping. So with this selected, let's go ahead and take a look at this situation that we have here. What I have is this hammer that I want to be able to swing down and hit the top of this nail. Now this hammer we can see is made out of two distinct pieces of geometry. If I swing this handle, obviously I want this hammer's head to stay connected to it. What happens if I were to just simply try to grab both of these objects and take my rotate tool and try to rotate them. You'll notice that each object rotates around its own pivot. So these two objects do not behave in any way like they're connected. So this is where parenting, or sometimes grouping, can come in. These are two distinctly different functions, grouping and parenting. So we'll see the difference between these two here in just a moment. But really either of these operations can be used in a situation where we need two or more objects to actually move together. So let's start with parenting. That'll be a little bit easier topic to grasp. With parenting, we have, essentially, one parent object and one child object. When it comes to parenting, the order in which you make your selections is very, very important because we are really telling Maya first what is the parent and what's the child. So when it comes to making a parent relationship, the first thing that we need to do is select the child object. What I want is a situation where the entire hammer rotates around this center that I've defined on this handle. I want the handle to be the parent, so when I swing the handle the hammer head will move along with it. Now keeping in mind that I wanted the handle to be the parent, I need to keep in mind that the handle will now be the last thing that gets selected. So start by selecting the child, shift-select whatever you want to be the parent. We can actually have multiple children connected this parent. So select all your children, make sure your parent's the last one selected, go to Edit, and then all the way down to parent. We can also just use the keyboard shortcut, which is P. So now you'll notice the hammer head is by itself. But now whenever I grab this handle, you'll notice that the head gets selected with it. Now this has not actually combined these two pieces of geometry. It's now just whatever I grab one it will now also control the other as well. Now if I grab this handle and move it, you can see the head moves together. OK? Here's the thing about a parent-child relationship, which is what we just set up. The child can still move on its own. As we can see here, I can grab the child and do whatever we want. Whenever we move the parent, the child goes along with it. So really think of a real life parent and any children that that parent may have. In the real world, you see a child following its parent. The child can still run around and do whatever he wants, really without the parent having to go along with him. Now if the parent moves somewhere, if the parent goes somewhere, the child has to follow. So really a nice set up that we can get here where we can still have independent control over both of these. OK. So again, that is parenting. Now let me try and undo a few steps here. We could actually see this hierarchy in a little bit more clarity if we were to actually open up what's called the outliner. To get to this outliner, just go to Window and down to outliner. That will pull open this little window, and we can actually see this hammer grip selected here. What's nice about this is we can expand this and actually see any children. So we have this hammer grip. Below this we have the hammer head. So what this is basically saying is whatever is at the top of this hierarchy is the parent, and underneath we have any children. Visually this might be a little bit confusing for you to look at because we have what appears to be two children underneath this hammer grip, and that's really not the case. What we have right here is really just the shape node for this piece of geometry. And this is the actual piece of geometry itself. As far as getting into the shape node, this is really not something that we're going to discuss in too much detail at this point. But for the sake of visual clarity, what we might do is just go into this outliner, right-click, and disable this option to show shapes. There we go. And now we can see these two pieces of geometry without any more interference from the shape nodes that they are also a part of. That's actually the shape nodes that we can see here in the channel box as well. What's really neat is the fact that we can break and make parental connections directly within this outliner. So let's say I no longer wanted this hammer head to be connected to this hammer grip. Well, all I would have to do is middle-click and drag this outside of this hierarchy. And now these are no longer connected together. You can see that there is no longer that parental relationship that links those together. And I could actually make that connection again. So if I wanted to, again-- and let's say we paired this the other way I'll take this and actually make this a child of the head-- I can take this hammer grip, middle-click, and drop it directly on top of this hammer head. OK. Now you can see whenever I select this hammer head that we have to now expand it. And we can now see that the hammer grip is a child. Again, if we take a look at this little link, anytime we see this, that means that there is a parent, or a hierarchical, link between these two objects. But now you can see we have a situation that is, basically, reversed. So now the head is the parent. Now if I rotate around the head, the handle follows. So that's a look at parenting. What I'll do is go ahead and take this piece of geometry and duplicate this. So I'll just grab this entire hammer head, control-D to duplicate, and move this over to the side. You can see that even a duplicated object still maintains whatever hierarchy we have contained within. Now on this duplicate object, I'll show you what grouping does. All right? And that way, we can actually see the difference between grouping and parenting. Before we actually do this group, let me go ahead and take this duplicate set here, and I'll take this duplicate hammer grip, middle-click, and drop this somewhere up above this hammer head. There we are. Now we have these two objects that are now separated. You can see there's no hierarchical link between those anymore. Now what grouping will do is take both of our selected objects and then put them inside of a child relationship, or actually put them as children underneath a new node. So I'll select both of these, go up to Edit and Group. You could also use the keyword shortcut, which is control-G. Now you can see both of these objects have been placed underneath this new group. So if I expand that, you can see the group is the parent. And these two have both been placed as children underneath it. So now we have the same parent-child relationship, essentially, where, in this case, we can grab the head, and you can see it moves completely independent of the handle. And the handle right now moves completely independent of the head because they are both children. If I were to come and grab the group that is the parent of both of these, you can see now if I rotate this group that now they move together. What you'll notice is that any time we make a group, it will put its center right down here at the origin, right where all of these different axes meet up. So any time you use a group, you'll probably have to come in and modify your pivot. So if I just press and hold D key on my keyboard, I can now come in, grab my pivot, again press and hold the D key, get that back to where I want it, and now I can rotate from here. So parenting, again, can be good if you find yourself in a situation where you have one object or more objects that you want to stay explicitly linked to another object no matter what. Grouping, on the other hand, can be useful if you have a situation to where you really just want the objects to be able to move together. It really doesn't matter which one is the parent and which one is the child. If we want to actually get to this group node, you'll notice at the moment, no matter which one I select, I can't actually get to the group. So if you have some kind of a situation like this, a quick and easy way of getting to the group node without actually having to go into the outliner to get it is to simply select an object that is part of a group, and then press the up arrow key on your keyboard. You can see now that will step us up through the hierarchy and grab whatever groups might be connecting both of these together. So as we start to get a little bit further through this course, and we start to get into topics like modeling and animation, you'll start to see where parenting and grouping become very, very important for situations where you need parts of your mesh to be able to move all together as though they are one piece. But maybe you still need to have independent control over these so that they can still move independently of each other if they ever need to. So for now, that's a quick look at parenting and grouping within Maya.