/ic/ - Artwork/Critique

So, I already have a basic understanding of perspective(pic is mine). I understand the concept of vanishing points, horizon line, boxes etc but i'm wondering in order to draw really good environments with character in it, just how much perspective knowledge do I need? Marshall vandruff's course is 7 hours while erik olson is 90 hours, what exactly am I missing in those other 80 hours? I'm also interested in making comics with sweet backgrounds like this http://www.mangahere.co/manga/kindred/c001/7.html

I heard ctrl paint had some good perspective info, thoughts on that?