An Introduction to 3D: Recreating the World Inside Your Computer, or Not - Blender Foundations: The Essential Guide to Learning Blender 2.6 - page 2

Let's take a look at the different elements of a real scene that we will need to analyze and rebuild in order
to achieve this.
Form
Everything that we see has a form—a physical structure. We know what these forms are: how a lion is
shaped, what it looks like when pudding falls on the floor, the essence of a chair.
The essence of a chair?
Well, what is a chair, anyway? There are thousands of different kinds of chairs, but when we see one, we
know it's a chair. That's because although the details differ, the form generally remains the same: a place
to rest your back side, some means of support (usually legs, but it doesn't have to be), and a back. If there's
no back, it's a stool. And so when we see an overstuffed recliner, a swivel chair attached to a table in a
fast food place, or just a basic dining room Queen Anne-style chair, our brain identifies the form and tells
us “chair.”
It is form that lets us know what things are. In the real world, form is made from matter. Yes, that's
“matter,” as in solid/liquid/gas from science. I know that no one said there would be science here, but
there is, as well as math—get used to it.
A lion's form is made up of organs, bone, muscle, skin, and fur. Pudding is made from milk, gelatin, and,
hopefully, chocolate. A chair's form is constructed of any number of things, including wood, metal, and
plastic. However, none of the insides really matter to our perception of the form. In general, we only see
the outer surface, and that is enough for us to properly identify things.
This is the first place that we decide as 3D artists that we will not simulate the world as it is, but as we
would see it through a lens. With a few exceptions, a camera only sees the outside surfaces of objects, so
that is all that we need to worry about. If we want to create images of forms (“pictures of stuff” for the
layman) we can temporarily forget about what things are made of and just focus on the shape of their
surface.
In 3D, surfaces are built from polygons , specifically triangles and quadrangles in Blender's case ( Figure 1.1 ).
Usually, these polygons are built from vertices, edges, and faces ( Figure 1.2 ).
These polygons are created and linked together in clever (or not-so-clever) ways until the whole surface
of a form is constructed. This construction is called a model . When making models in 3D, it is important
to keep in mind how their form will be shown in the final image. If the image of the object will be very
small, perhaps because it is far in the distance or just a tiny detail like a flea or a grain of sugar, the model
can be very simple ( Figure 1.3 ). There would be no need to create a model of a building in exhaustive
detail if it appeared only one-quarter inch high on a distant hillside in the final image.
We know what the form of such a building is in the real world. It has a roof, a chimney, windows with
trim, maybe a spigot for a hose, and many other details. However, when we look at the 2D image with
a critical eye, we can see that for our purposes, the building is little more than a box with a triangular