3D Modeling Fundamentals

3D Modeling Fundamentals

3D modeling is the process of creating a mathematical representation of a three dimensional object using specialized software. Every object you see in a CG movie or video game started as a 3D model. The model defines the shape of the object, and everything else, the texture, the material, the animation, is built on top of that foundation. A good model is the starting point for everything in 3D.

The most common way to build 3D models is with polygons. A polygon is a flat shape with three or more sides, usually triangles or quads. Thousands or millions of these tiny polygons are connected edge to edge to form a mesh that approximates a surface. More polygons mean more detail, but also more processing power needed. A model for a movie might have millions of polygons, while a game model might use only thousands.

Vertices are the corner points where polygon edges meet. Edges are the lines between vertices. Faces are the flat surfaces enclosed by edges. When you move a vertex, you change the shape of all the faces connected to it. This is the fundamental operation of polygonal modeling. You push and pull vertices, create new edges, and extrude faces to build up the shape you want.

NURBS, or Non Uniform Rational B Splines, are an alternative to polygons. Instead of flat faces, NURBS use mathematical curves to define smooth surfaces. They are great for organic shapes and industrial design because they are mathematically precise and smooth by definition. However, they are harder to work with for complex models and are less common in VFX pipelines today, having been largely replaced by subdivision surfaces.

Subdivision surfaces combine the best of both worlds. You model with a low polygon cage that is easy to manipulate, and the software automatically subdivides it into a smooth surface. This gives you the control of polygonal modeling with the smoothness of NURBS. Most modern VFX modeling is done with subdivision surfaces. You can always increase or decrease the subdivision level depending on how much detail you need.