# 3.1 - Introduction - Describing Virtual Worlds¶

To create a rendering of a virtual world we need to be able to describe the
world. We assume that a world is composed of objects. We need to *model* the
following properties of each object:

- its location - where is an object in reference to the scene?
- its orientation - which way is the object turned or facing?
- its volume - what 3-dimensional space does the object take up?
- its surface properties - what color is the object? Is the object smooth or rough?

Our description of the world must be in mathematical values, symbols and operations that a computer is capable of manipulating. This means you need to understand some math! But don’t let the math scare you. The math will be introduced slowly with plenty of explanations and examples. Just make sure you fully understand one topic before proceeding to the next. The math is more easily understood in 2-dimensions, so we will introduce the ideas in 2-dimensional space and then extend them to 3-dimensional space.

So let’s start with the basics of location and build from there...

## Glossary¶

- virtual
- Something that does not physically exist but is created by software to appear real. A virtual world is a simulated, artificial, imitation of the real world – or a make-believe world that exists only in your mind.
- object
- A single entity in a virtual world that has a location, takes up some volume of space, and can be moved, scaled, and rotated.
- model
- A mathematical description of an object.
- scene
- A collection of objects that make up a virtual world. A scene contains objects that we want to visualize.
- rendering
- The process of creating an image from a collection of virtual objects. The image is a representation of what is visible from a virtual camera. The objects are only visible if there is virtual lighting in the scene.