Your Erection Direction - A Specific Cause or Totally Random?

I've honestly never noticed if it curves upward or downward at all. It very obviously curves to the left, though, as evidenced in my morning wood pic.
 
It seems to be a slight correlation between a downward curve and a longer cock. You can check the n-curve (downward) gallery versus the u-curve (upward) gallery at www.erectionphotos.com for more information.
 
Upward, curved, and points slightly to the right. I've always assumed it was because as a kid I'd always point my (limp) cock up and to the right in my briefs, long before I could get hard and continued to so into my early teen years. I switched to pointing it down as I hit highscool when I was getting random hard-ons checking out the girls and it was showing. Still I'd point it down and position it on the right side with my balls on the left. I guess it's too late to reverse the configuration I'd put my cock it. The upward curve though I have no idea how I got it.