>>404
DirectXSDKのヘルプみろよ
あれが最も丁寧でわかりやすい。
http://www.microsoft.com/japan/msdn/library/default.asp?url=/japan/msdn/library/ja/directx9_c/directx/graphics/programmingguide/fixedfunction/transforms/projectiontransformation/whatisprojectiontransformation.asp