I believe what happened was 'they' filmed this movie, watched it, scratched their heads and acknowledged that what they had created was, by all accounts, awful and cliche. However, the director/ producers, being the optimists they undoubtedly are, instead of admitting defeat, had the fantastic idea to add a nude chase scene, make the carnage gorily brutal and put it all in 3D.
My advice to you is this: Think of it as a comedy, as the plot is utterly hilarious, get into the moments that make you jump (and there are a good few), and walk out about 10 minutes before it's over. The end is disappointing and the monster is much more interesting before you find out how lame he really is.