Hi,

I believe like mastone said it's down to filter size and map size. With depth map shadows the light basically projects a texture into the scene and creates a shadow map based on it. If the texture is too small then you will get stepped edges, unless you use a larger filter size (which will blur the stepped edges together, simulating soft shadows). If you want sharp shadows you need to use a larger map size but with a lower filter.

So small map + high filter = soft shadow edges.

Large maps = sharper shadows.

Hope that helps,

cheers

gubar