Quote: "when i add finish with 3d grass becouse it will certanly have many , many poligons..."
That method can be a real bugger to do, what I think would be useful its to get a plane, give it a grass blade texture with black or white space around the grass (two or more grass blade on the texture is more efficient) and then apply the texture and the texture again but as an alpha map, then you should have easier low poly grass, its what they tend to do in games sometimes...
OR
Does your program handle displacement maps? (I might be able to figure out a good grass technique with displacement maps)
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