# Alpha Map

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Hi all, can somebody tell me what exactly Alpha Map is and what is it used for? I came across this word but couldn't find any definition or simple explanation. Thanks in advance. Y.

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Alpha means opacity in graphics, so with an alpha map you control opacity of the rendered primitives/image.

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Well, i know what alpha in graphics terms mean, what i meant was what are "Alpha Maps"? I might not put this question in a correct way. I think it's kind of a technology to produce some "special" effect or something. If I sound too stupid sorry about that, i'm rather new to these topics ;o)
Thanks.

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An "alpha map" is just the same as a texture map. It is a texture applied to the surface of a polygon (or mesh of polygons). The texture is then used to control the opacity of the underlying polygons.

So, say you had a tree model. You might model the leaves by creating a few quads. You could then use a leaf texture over the quad, but you wouldn't be able to see through gaps in the leaves. If you used an alpha map, you could make some parts of the quad invisble (the gaps between the leaves), so it appears as if you are actually using more geometry than you really are.

Hope that explains it well enough for you!

Steve

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A 32-bit Texture (some other formats too) has 4 channels, each channel has 8-bit values so they range from 0-255. The first 8-bits are for the Red component of a pixel, then come the 8-bits for the Green component and then come the 8-bits for the Blue component. The remaining 8-bits (32-24=8, y'know) are mostly used for as an alpha channel or an 'Alpha Map' as some people might call it.

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Thank you guys for your replies, i thought it's some kind of brand-new technology for doing "something". I see the things much clearer now. ;)
Thanks again. :o)

Y.

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