While I cannot speak for why you were downvoted, I can give my own opinion on the quality of the posts, and what I would do to make them better.
For the initial shadow mapping topic post, embedding it in code blocks would have helped readability. I tend to do that at about 3 lines, usually. You can either use the angle bracket button that looks like <> or you can use the board tag [code]code goes here[/code] if you are using bbcode markup.
For your followup #4 you revised your original question rather than adding new information. While it was good that you pointed out it was an edit to the original question, it would have been better if you just added new information on a new post. Usually editing is for something you notice immediately after posting such as spelling or grammar errors, not for changes after others have replied. It is bad form to modify questions after others have written some answers or otherwise followed up. You also wrote down assumptions that changes had no effect, which sometimes is not true; you may not notice the effect of a change, but it can mask other issues.
For the original most efficient method post, that's the kind of factual question Google will readily answer, and generally you aren't looking for "most efficient" for that sort of thing, but "easiest to use". Not enough to downvote for, but something I'd recommend searching for yourself (and learning the answer) rather than asking to be spoon-fed answers.
And finally... you've only got 3 posts outside of this thread. That is WAY too early to be worrying about reputation. Reputation is a general gauge. Perhaps after ten or twenty posts you'll see a pattern of +1 or -1 on various posts. Usually providing answers is what gets the upvotes. When you've had a few hundred posts and start ANSWERING rather than ASKING questions, reputations skyrocket.