As far as i know , you cant use alpha-testing in XNA 4.0. Am i wrong?
You certainly can, there's an
AlphaTest effect built in for it. Or do the alpha testing in your own shader (it's shader-based in 4.0, like clipping planes).
As for using it, I think the biggest thing you have to worry about is the aliasing. You get a freebie in terms of not having to order it (since the pixels that are rejected are simply rejected, rather than the pixel being kept and blended with whats underneath it), but you may have ugly cut outs. But if you use pre-multiplied alpha you can reduce those artifacts (as described by the links Moe posted).
It seems Shawn is posting a lot about anti-aliasing these days, heh.
