Understanding the importance of object hierarchy
Video: Understanding the importance of object hierarchyCINEMA 4D, more than any other application, is entirely dependent on the relationships between objects in order for it to function. It's absolutely crucial that you understand those relationships before moving on with CINEMA 4D. There are three primary relationships in CINEMA 4D between objects and it's parent, peer, and child. And there really is no better example than our own solar system. Now, in this animation you can see we've got a sun, each of the planets lined up in rings outward from the center.
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CINEMA 4D Essentials with Rob Garrott is a graduated introduction to this complex 3D modeling, rendering, and animation program, which breaks down into installments that can be completed within 2 hours. The first course in the series introduces the CINEMA environment and illustrates the importance of the object hierarchy. Discover how to navigate within your projects; how to configure the application preferences; set up a project properly; and create objects and change their parameters. Rob also explains the different object types and the principles behind creating a model with primitive shapes.
Understanding the importance of object hierarchy
CINEMA 4D, more than any other application, is entirely dependent on the relationships between objects in order for it to function. It's absolutely crucial that you understand those relationships before moving on with CINEMA 4D. There are three primary relationships in CINEMA 4D between objects and it's parent, peer, and child. And there really is no better example than our own solar system. Now, in this animation you can see we've got a sun, each of the planets lined up in rings outward from the center.
The sun is the parent of the entire solar system, and each of the planets are children of that sun object. And then each of the planets in turn are peers of one another. Some of the planets have moons. The moons are children of the planets, and the moons are peers of one another underneath each of those planets. That really is a great illustration of how the parenting relationships behave inside of CINEMA 4D. The sun moves around the galaxy, towing along all the planets, but the planets themselves can move independently of the sun as long as they travel with the sun.
The same goes true for the moons surrounding the planets. The planets themselves circle the sun. The moons travel along with them in their own orbits as children of those planets. And yes, I do believe Pluto is a planet, contrary to the scientific community. I have no basis for that. It's simply belief in Pluto. So, let's move over to CINEMA 4D and take a look at this relationship in a little more detail. It's not important how I created these objects right now. What I want you to focus on is the relationship to one another.
Here in the Object Manager, I've got a whole bunch of things listed. Let's twirl close the Camera Parent. And right now we're looking through the camera. If I hit play in the interface right here, you can see the exact same animation with all the text elements that we saw in the movie example. Now, let's zoom in a little bit closer here. You can see, as we pull out, the planets themselves are orbiting around this central figure of the sun. Now, in our hierarchy here, in the Object Manager, we've got some very important lines here that describe the relationship between these objects.
So over here on the left is the object hierarchy line. It goes off the very top of the Object Manager, and this indicates the root level of the hierarchy. Now, below these objects are their children. So for example, if I twirl close the Solar Parent, I've just hidden all the children below it. If I twirl it open again, I've revealed all those children. Now, the sun is a child of the Solar Parent. The Solar Parent is at the very center of the solar system, and the sun is a child at the very center of that Solar Parent.
The Mercury Parent is at the center of the world as well. However, Mercury is offset from that Solar Parent, and it's offset the distance of its orbit. Let's scrub to the point where they're all lined up. And so you can see that the object that is moving Mercury is this Mercury Parent, and it orbits around the center of the sun the same way that Mercury orbits around the center of the sun. So in order to establish this relationship, I had to create a parent-child relationship between Mercury and this null object that is Mercury's parent.
And I did the exact same thing for each of the planets. This object called a Sweep NURBS is what's creating the white line that's surrounding the sun in the orbits of each of the planets. So, let's take a look at the Earth system. If I scroll down here, you can see that I have an Earth Parent. It's at the center of the solar system, right in the middle of the Sun. The Earth local parent is at the center of the Earth, but it's offset relative to its parent. And then the Moon Parent is at the center of the Earth as well, but the moon itself is offset, and so I have the ability to rotate that Moon Parent.
So, I will hit the letter R on the keyboard. I can now grab the Rotate tool, and I can use these things called Axis Bands to rotate the moon around the Earth. So, you can see that the orbit is determined by its relationship to its parent. Let's take a look at one more example. Underneath the Mars Parent, Mars has two moons. I think they're called Phobos and Deimos, I believe. And they are two little potato-shaped moons that are orbiting right around the planet.
Let's uncheck the Active Camera icon. Let's twirl open the Camera Parent and uncheck the Active Camera icon. You get this little swoopy animation. Now we're looking through the editor camera, and I can zoom in on that without messing up my camera animation. Let's zoom in on Mars, which is this little red planet right here. And now I can orbit around. I'm using the 1, 2, and 3 keys to do my navigation. So within the Mars Parent, the Mars Parent is at the center of the world. It's off camera right now. And you can actually see, this little blue indicator tells me that the thing I have selected is off camera in that direction.
Now, the Mars null object is the parent of both the Mars planet and the moons. Now, underneath that Mars planet parent is the moon parents, and the moon parents are at the center of the world as well. And these two moon parents are peers of one another underneath Mars. They're also children of the Mars object. So they're peers of one another, and they're children of Mars. The same thing goes for the Mars planet. It's a peer of these guys. They're at the same level of the hierarchy.
Now, if I twirl them open, each of these Mars moon parents has its own moon--Phobos and Deimos, unless I got that backwards. And as I rotate the Mars moon 1 Parent, I can grab the Rotate tool by hitting R on the keyboard, and I can grab that Y-axis band and I can rotate that around the center of Mars. Why does this all work? This all works because of a very important concept, and that's the concept of relativity. Now, let's make a new document--Command+N or Ctrl+N on the keyboard--and talk about that concept of relativity.
It's very, very important, and directly related to those parent, peer, and child relationships. I'm going to add a new object to the scene. Let's add a cube. Then I'm going to add a second object. Let's add a sphere. So, I click and hold on the cube and drag to the right until I find the sphere, and I let go. Now, when you add objects to CINEMA 4D, they show up in exactly in the center of the world. Now these two objects are right inside of one another. You can see, as I hover around, it's trying to decide which one I want to try and select. I normally select objects inside of the Object Manager so I know exactly which one I'm getting.
So, I'm going to click on the sphere, and let's move the sphere outward away from the cube and just grab the red axis handle for that. This red axis handle allows me to move the sphere along the X axis. In order to parent these objects up, I'm going to take the sphere and drag it on top of the cube. You see how the icon changes. When I let go, the sphere is now a child of the cube, and you can see that it's indented. They are no longer at the same level of the hierarchy. Now, if I select the cube and hit R on the keyboard to bring up the Rotate tool, I can grab that rotate axis band and drag them.
You can see that the sphere now orbits around the center of that cube along with it. And if I grab the sphere, I can still orbit the sphere independently. I can also move the sphere around. I'll undo that: Command+Z or Ctrl+Z. Now, there's a very important concept about relativity. Let's take a look at the properties for the spheres. Let's select the sphere. Let's raise this up just a bit. The Attribute Manager shows me the properties for the sphere itself. We've got Basic, Coordinate, Object, and something called Phong.
Let's look at the Coordinate properties for the sphere. The Coordinate properties of a sphere show me the location of the sphere relative to either the parent or the center of the world. Right now, the parent for the sphere is the cube, and it happens to be at the center of the world. So, the value that I'm seeing here, -432, is exactly where the sphere is. Watch this. I'm going to take the cube and move it on its X axis away from the center of the world.
Now, I can see that the X axis value for the cube is set to -300. Let's make the math easy. Let's make it -300 exactly. Now I just highlighted that text and then typed in the values. On the sphere--let's select that-- you can see it still shows us the exact same value that we had in there before, -432, even though I know that it's moved over. That's because this value is relative to the parent. If I take the sphere out of the hierarchy by clicking on it and dragging down in the Object Manager, now they're at the same level.
Look what happened to the value for the sphere. It inherited that additional 300 units on the X axis, and now its value is -732. That's because it took the 300 distance from the center of the world to the center of the cube, plus the distance from the sphere to the center of the cube. So, it inherited that value. That's really important to understand, that objects inherit values from their parents. Let's see what that means for scale. I'm going to delete these two objects, and then I am going to add a cube again.
And let's add this time a pyramid. So, the pyramid object is right down here. I will add that. And you notice they show up in the center of the world again. Let's take that pyramid, and I'm going to drag it on the positive X axis this time. So now they're side by side. Let's take the pyramid and parent it to the cube. Oops! I missed that time. You can drag it right onto there. Now, you can see that it's indented. Scale is a really important thing to keep in mind when you're working with parents and children. And remember, they inherit their values from the parent. And Scale can be a really tricky thing.
As a general rule, I only ever change the Scale value here in the Coordinate properties when I'm animating. I never use that to model. And the reason is that let's say, for example, I want to make this cube taller. I'm going to take my pyramid out of the hierarchy, and I make the cube taller by changing the Y value here from 1 to 2. Now, my cube got taller, and I can put my pyramid back into the cube hierarchy. Now, when I select the cube and look at it, its value says 1 by 2 by 1. When I select the pyramid and look at its scale value, it's set to 1 by 0.5 by 1.
That's because it is roughly half the size of this pyramid based on the scale relativity. Let's grab the Rotation tool by hitting R on the keyboard. If I rotate this pyramid--I'm going to grab the Y axis band and rotate the pyramid around its Y axis--everything looks normal. Now, watch what happens when I grab the X axis band and rotate the pyramid around the X axis. Whoa! My pyramid has become distorted. That's because it's trying to rotate through the Y value scale that it's inheriting from its parent, and so it's being distorted along the Y axis relative to the parent.
Now, it's very important that you keep that in mind as you're working with your object relationships. Children inherit the Scale value from their parent, and that Scale value gets translated down through the hierarchy and can cause weird distortions in your objects when they animate. Object relationships really drive all of the functionality inside of CINEMA 4D, and it's really important to get a handle on understanding them before you move on.
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