Alpha mapping is one of the most basic skills you need to know in CG. This tutorial will give you the run down on what alpha mapping is and how it can help your texturing process. The tutorial itself was done with 3dsmax, but alpha mapping is applicable in any application.
So what is alpha mapping you ask? Well alpha mapping breaks down black and white maps to be information rather then color. Basically black is seen as OFF and white is seen as ON. How is that useful you ask? Max can use this with a number of material maps to give you different effects. Say you slap a checkered black and white map in your opacity slot of a standard material, max will leave your black-checkered squares their original color while changing the white-checkered squares transparent.
	Easy enough right, so lets dive in a little deeper. We know that Max sees White as On and Black as Off, but it can also use all those grays in between Black and White. Go back to our opacity slot and change the color to pure gray. The result will give you a 50% transparency. The closer you get to pure black the less transparent it will be, vice versa the closer to white the more transparent it will be.
Pretty simple but max can still do more with it, not only can it see an alpha map as either an on or off it can see a color as a percentage of Height or Depth. When we work with displacement maps max will use the alpha map as a percentage of our set total height or depth. So say we set our displacement map to 400 and apply an alpha map with a black square, a white square and a pure gray square. Each square will take a percentage of your set value so white would be 400(100%), grey would be 200(50%) and black would be 0(0%).
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