From the smallest blade of grass to the most life-like characters, everything in CG Animation starts with the modeling process. 3D modeling is the art of creating a representation of a three dimensional object, real or imaginary. It is the basis of the virtual worlds in video games, movies, architecture, TV Commercials and much more. 3D modeling closely resembles sculpting, in the sense that complexity is added bit by bit to the base form until the artist arrives at the desired result. In the world of 3D, different techniques can be used to create a shape and clay is replaced by polygons.
Box or Primitive modeling – This technique is the most simple and straightforward. It consists of utilizing the basic shapes that can be created automatically with Maya, such as cubes, spheres or cylinders, and building objects out of them (For example, a chair might be built out of 4 cylinders for it’s legs and 2 cubes for the base and back). It provides little flexibility and is impractical for detailed models. However it can be valuable as a tool to block out early stages of a model, for establishing proportions or even to create placeholder objects for animation previews.
NURBS (Non-uniform rational basis spline) modeling – With a cryptic name, NURBS modeling is a useful technique that uses complex mathematical algorithms to describe curves and surfaces. It produces perfectly smooth and accurate surfaces that are easily editable. NURBS modeling is generally used when the intended surface does not require localized details and needs to be perfectly aligned and smooth. They are widely used in vehicle modeling and in the creation of objects that require technical precision. In Maya, the NURBS primitives and modeling tools can be found in the Surfaces shelf. The revolve tool uses a NURBS curve to define an object with a radial symmetry. The loft tool uses several different NURBS curves to define a smooth surface between them. More in-depth and advanced tools can be accessed by switching the menu set to Surfaces. This reveals the “Edit Curves” and “Edit Surfaces” menus which contain more options than those available from the shelf.
Polygonal modeling – By far the most widely used and versatile technique, polygonal modeling or polymodeling allows for direct manipulation of the building blocks of a 3D model. This is what you need to get familiar with if you want to learn how to model in maya. Polygons are the smallest visible structure that make up any 3D model, in Maya they are called faces, they are made out of at least 3 vertices (or points) and 3 edges and these structures form what is called a mesh. With polymodeling, the artist has full control over the mesh of a model by moving around vertices and edges and adding polygons to increase the complexity of the model.
Polymodeling can be used in all situations, especially when there is a need for detailed surfaces both organic and inorganic. Everything from characters and their clothing to landscapes and vegetation is typically created using polymodeling. Maya’s polygonal modeling tools can be accessed by switching the menu set to Polygons and via the Polygons shelf. Maya uses selection modes to define which sets of tools are available at any given moment. From a polygonal object’s contextual menu it’s possible to select either the vertices, edges or faces of the object and apply operations to each of them. Useful tools include the extrude face tool, it takes the currently selected face and “pulls” it outward creating a new face along with a connecting set between the original and the new faces. The extrude edge tool is one of the most used tools in 3D modeling, it is similar to the extrude face tool but creates only one polygon between the old and new edge. Another widely used modeling tool in Maya is the split polygon tool, which allows the artist to cut faces at will and refine the model. These tools are used to create the base shape of the model that generally is intended to be smoothed out. Smoothing in 3D modeling is the process of automatically increasing the number of polygons and averaging their positions so that the result is a smooth mesh based on the hand modeled faces. This is because polymodeling, as opposed to NURBS modeling, does not by itself result in a perfectly smooth surface yet smooth surfaces are required for high-resolution models. This means that something like a model of a human face has to be crafted polygon by polygon to the desired level of complexity and then smoothed using Maya’s mesh smooth option. For smoothing to work properly, the artist needs to keep in mind that when using the polymodeling technique, all faces should be quads. A quad is a face that is made of 4 vertices. Quads create clean and smooth geometry. Faces with only 3 vertices result in unwanted artifacts when the smoothing is applied to the model. Faces with more than 4 vertices might result in incompatibility with other applications, especially real-time engines. An important point to consider is that faces with more than 4 vertices, called n-gons (for a polygon with n number of sides) produce very bad animation deformations, this means that something like a character should never have any n-gons in it’s geometry.
The type of work being done and the final result will dictate which technique to use. Ultimately, most models are done with a combination of all techniques. A model of a car for example is created using many different parts, some parts of the body might be easily created using NURBS surfaces while other more detailed areas require the finesse of polygonal modeling. Good judgement on the usage of each technique comes with experience, practice and study of the topology of an object. 3D Modeling might be the start of the process to create amazing CG visuals, but it is a deep and complex field that benefits from the creative use of the available toolset.