Paper: http://research.microsoft.com/en-us/um/people/larryz/zitnicksiggraph2013.pdf

I've been trying all day to understand what the authors of the paper do under the heading 3.1. Up to that point I had a fairly clear idea of what they were doing and how they were doing it. Then I reached that point, trying to first understand it by rewriting it in my own words followed by implementing it.

However, I can't even rewrite it in my own words, I simply don't understand what they're doing. How would I go about understanding what they're doing so I can implement this algorithm myself? Do I need to study more math? Should I read other easier papers first? Get specific help with this problem?

Any advice is appreciated.