Normals
Most of the time people don't understand what a normal really is. It is more than just the way your model is shaded or smoothed. It's the way your model is put together. Without normals, all you would have is polygons sitting in 3d space. This subject came up to me when I was on the Area's forms. I noticed Longboarder1 had asked a question about normals.
A normal tells Maya the way to fit and set up polygons. A normal can also tell Maya the wrong way to fit together. Hopefully in this tutorial I will help you understand and fix normal related problems. Basicly this is a crash course.
The Basics:
In this example below it shows a model with two different normals. The one on the left has it's normals set to 0. The one on the right has it's normals set to 1.
Image Description: The one on the left has it's normals set to 0. The one on the right has it's normals set 1
They're both the exact same geometry. The only difference is their normals. So why does this happen? Imagine a normal is like a way of rounding off edges of polygons. In the diagram below, it explains how Maya does this.
Normals and how they hold together geometry:
Ever wondered when you just combined two different polygons together and you go to append tool and it doesn't work right? For just about every scenario this will be a normals problem. The image below explains how this works.
I hope this tutorial has helped you improve your modeling experience. These techniques should work in most cases.The best of luck!