# 4.1 - 3D Modeling¶

3D modeling is the process of developing a mathematical representation of
an object. The result is a **3D model** which
can be used for rendering 3D scenes or to prototype newly designed widgets.
Creating 3D models is an art that requires extensive training. In the
movie and game industries people often become experts at 3D modeling and that is
their sole job. The next time you watch a movie that contains special
effects using CGI, notice the number of modelers that are listed in
the credits at the end of the film.

Note these characteristics of 3D models:

- The goal is to represent the form of an object, so an object’s surface is often the only thing that is modeled. There are exceptions, such as a model for simulating the inner workings of an engine.
- A 3D model is a typically a polygonal mesh, which is a set of
connected polygons. Polygons with more than 3 edges are converted to
triangles for rendering. These are called
*triangular meshes*. - The number of polygons used to represent the form of an object determines the accuracy of the model. More polygons means greater accuracy, but at the expense of more memory requirements and slower rendering.
- The total number of triangles in a scene is often the deciding factor
in whether the scene can be rendered in under 1/30
^{th}of a second. It is common to reduce the number of triangles in one model so that another model can have more. - A model is manipulated as a unit. If parts of an object move independently, then those parts must be modeled separately. For example, if you have a box whose lid opens, this would be modeled as two separate objects - a five sided box and a lid.

## Modeling Software¶

There are many software applications designed to help a modeler create 3D models. Here is a partial list. Commercial modeling software can be very expensive. For example, a single license for CATIA is $65,000 with an annual maintenance fee of 18% (1). We will use Blender for these tutorials, which is a free, open source modeling and animation program.

## Glossary¶

- 3D model
- a mathematical representation of an object.
- polygon
- a flat area enclosed by a set of connected edges.
- polygonal mesh
- a group of polygons that define the surfaces of an object.
- triangular mesh
- a group of triangles that define the surfaces of an object.
- modeling software
- a software program that facilitates the creation of 3D models.
- modeler
- a person who creates 3D models.
- Blender
- an open source, free modeling and animation tool.