From the course: Maya: Natural Environments

Understanding scene scale - Maya Tutorial

From the course: Maya: Natural Environments

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Understanding scene scale

- [Instructor] The most fundamental consideration when beginning a natural environment project is seen scale. How big are the objects in your scene? You're going to need to work within the requirements and limitations of whatever application you're using. So for example, a game engine may have very hard limitations and very hard requirements of exactly how large things need to be. The same can be said for Maya to an extent. Even though Maya is more of an open framework than a game engine is, Maya still has some limitations that you need to work within. Let's talk about scene scale. So think of Maya as a little mini universe, kind of a little bubble universe in itself. And that universe actually has its own rules, it has its own sort of laws of physics if you will. They're not the same as the laws of physics in the real world. One big difference in the computer realm is that the accuracy of calculations of things like where an object is those calculations are more accurate. They're more precise. The closer you get to the origin or the center of the world. As you move farther and farther away from that origin, the calculations become less and less precise and you may encounter issues called round-off errors in which, for example geometry collapses on itself and crumbles or objects don't render because they're too far away. So this is kind of counter-intuitive it's not the way the real world works but it absolutely is the way the Maya works. Now, those limitations are determined by how Maya was coded, how it was written way, way back at the very beginning in Maya 1.0. At that time, the developers decided that "Maya will have system units," and those system units will be undefined. So a system unit is a unit of measurement within the sort of digital matrix of Maya, the sort of structure of the universe. But those units do not have any correlation to units in the real world. And that's good because it gives you the flexibility for building things at whatever scale is convenient to you. But it's also bad because it doesn't give you any guidance or reference point of how large you should build something. And so beginners in Maya often run against this problem very commonly, they don't know how large to build something. Now, if you come from an engineering or a CAD background, then you're going to think, well, I should build things in my 3D world the same size as they would be in the real world. So a human would be built to be approximately let's say 180 centimeters tall. And that makes sense in a lot of cases. It does not make sense in the case of a Maya natural environment. So if you attempted to build an environment that was at one-to-one scale, that was measured in the working units of Maya, to be the same size it was in the real world, you would get round off errors, you would get problems. You can't actually build something in Maya that's larger than let's say 10,000 or at the very most a hundred thousand centimeters in size. That's really small. So you can't build something that's, let's say actually 10 kilometers off to the distance. You will have major problems. Like I said, geometry will bramble, objects will render, you'll get confused. You'll think that something's not there when it is and it's a major problem. You actually cannot work that way. So how do we deal with this? The solution is to let go of the idea that an environment has to be at one-to-one scale. We need to build an environment at a miniature scale in Maya for it to work properly. Let's take a look at the example here. I've got a scene built at 1, 100th scale and that is the scale convention that I recommend for Maya and natural environments. If I select the terrain object, go over to the channel box and in the inputs, open up the plane primitive which is labeled polyPlane 2 we'll see that it's got a width, the height of 500, of 500 what? Well, in this case it's 500 centimeters. Because those are my working units. So let's investigate that. We'll go into the windows menu, to Settings Preferences, Preferences, and then to Settings. And then we have a field here a pull down list, for the linear working units. And the default is centimeters. It's important to know that the working units have no connection to the system units. The system units are fixed. They're hard coded into Maya. There's nothing you can do to change the system units or their accuracy. You can do that in some programs like 3ds max and then makes it easier to accommodate very very large or very, very small scenes. But in Maya, there's no such mechanism. We can't adjust the inner workings of the system units in order to optimize calculations. All we can do is choose a working unit that represents some real world measurement. We will change the linear working units, but that will not change the size of objects and it will not change the accuracy of calculations. So I can change the linear working units over to meter. Now my polyPlane primitive reads out of width and height of five meters. So that's really all the working units does, is it changes the numeric fields that represents some distance. So we can change that back to centimeter and it goes back to 500 centimeters. Either way the object has an absolute size of five meters or 500 centimeters. So changing this doesn't change the size of objects or how accurate the calculations are. So what I've done here is I've constructed this terrain to be 500 centimeters on a side. And I'm just imagining, I'm just contemplating in my head that this is actually not 500 centimeters, but actually 500 meters. 100 times larger than it really is. So again, I've constructed a scale model at 1, 100 scale and that's really the only way you're going to be able to build a natural environment in Maya. We're going to take a little bit more deep look at this but that's where you need to start. You need to start from the concept of leaving your working units at centimeters, but then just imagining in your head that it's actually in meters. Then if you build your initial primitives according to those scale parameters and everything will come out to be 1, 100 of its original scale.

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