Every 3D application has a collection of shapes very well known named 'primitives'.
These stock shapes, whether polygon or NURBS based, are called primitives.
Although primitives vary a bit from 3D application to application, most include a cube, sphere, cylinder, cone, and sometimes a pyramid.
Now, although these shapes are the most basic of the three-dimensional shapes available, don't underestimate the power of them.
Primitives render quickly and are usually optimized as far as poly-count goes.
If you can relay your design using primitives, that is a good idea.
For instance, some great examples by talented artists of primitive-based shapes that end up creating not-so-primitive models and scenes are a very good example.
Extrusions, Lathing, and Skinning Most 3D modeling takes the form of creating some sort of two-dimensional or quasi-two-dimensional shape and altering it or adding other two-dimensional shapes and then placing a "skin" over the top of it to create a three-dimensional shape.
3D applications usually provide tools for creating the two-dimensional shapes (splines, NURBS or others) that will be used to extrude, lathe, or skin.
However, if you are not comfortable with your application of choice's spline creation tools, or if you just want more control, most all programs will allow you to import paths from other applications such as Adobe Illustrator.
So, when first getting started with the techniques described next, you may want to create your source two-dimensional files in a program you may already be comfortable with.
Think of extrusion like the Playdough spaghetti makers.
Remember how they have some sort of template with holes cut in them that when Playdough is pushed through it, it takes on the shape of the hole? If you use the round-holed template, the Playdough comes out in long, round tubes.
If the star template is the tool of choice, the star-shaped spaghetti emerge.
In a nutshell, extrusion is taking a two-dimensional shape and pulling it into a third dimension.
Notice also that you can add a bevel to extrusions to give them a different sense of depth.
The extrusion profile refers to the path the source two-dimensional shape takes as it extends into three-dimensional space.
Therefore, if the extrusion profile is straight, the shape goes straight back; if it is curved, then the object will be beveled.
Different applications have different ways of referring to these bevels.