 In this video, we'll be discussing geometric theory and how it applies to 3D models. So first of all, let's discuss what a 3D model actually is. A 3D model is a mathematical representation of a shape in 3D space. Cubes, spheres and cylinders are all examples of basic 3D models, but they can also be very complex, as you can see in these examples. There are two main types of 3D models in use in the films and games industries. These are NURBS surfaces and polygonal models. We're mostly going to focus on polygonal models, but I'll also give a quick explanation of NURBS surface modeling. So a NURBS, or non-uniform rational B-spline surface, is a model created through the use of bezier curves, like the ones used to create vector graphics. To form a NURBS surface, the software interpolates between two or more curves and creates a smooth face to fill the space. Models constructed using NURBS are very mathematically accurate and commonly used for modeling for engineering and automotive design. Polygonal models. These types of models are more common in the film, animation and games industries, and it's these that we'll focus on for the rest of the video. Polygonal models are made up of vertices, edges, and faces. Vertices. These are points in 3D space. Each of these points is known as a vertex. Each vertex has its own coordinate information, so x, y, z values. And moving these vertices is a common method of shaping models. In this example, you can see vertices highlighted in a mesh. Edges. Edges are used to join vertices together. This creates a wireframe like the one you can see here. Faces. The thing that defines polygonal modeling is that the meshes are faceted. This means that they are made up of faces. Faces are used to fill the space between the vertices and edges. In efficient modeling, these faces are three or four-sided, known as modeling in trizoquads. The faces that make up a 3D model is known as a mesh. The number of faces in a mesh is known as the polycount, and the polygon density is referred to as the resolution. 3D coordinate space and axes. The three-dimensional space that gains an application such as Maya Relayon is based on the Cartesian coordinate system. This is like a map for defining the position of points in 3D space. The system was developed by French brain box René Descartes. Using this system, space is defined using three axes, known as x, y, and z. These represent the width, height, and depth, respectively. The coordinates for a point are written numerically in the order of x, y, and z, and look something like this. The zero point of the axes is called the origin, or 0, 0, 0. This is where each of the three axes intersect. Here is an example of how this coordinate system looks and works. Okay, so that wraps up the anatomy of 3D models. And how they're created. Hopefully this has been useful. Don't forget to give this video a thumbs up and subscribe to the channel for more fantastic videos like this. And I'll see you in the next one. Bye.