Dan's answer is very good, and I want to add one more point:

Accept that on the first pass you will not be able to fully understand the topic. Appreciate that there are decades and sometimes centuries (for the math, at least) of research supporting the topic you're learning. Thinking you can "get to the bottom" of it in a few months, let alone a week or two, is not realistic. Choose a topic and try to understand that as much as possible. Keep notes on other interesting topics along the way, but don't get distracted by them; just accept them as assumptions as this point and move on. You can get back to them later.

This is a common problem. Self-directed learning, with no boundaries or focus, can easily become aimless and unproductive.

To overcome it, try to find some sort of replacement for the structure that would come in a formal education program. This could take various forms, but here are a few examples of things you could try:

• Make a plan for yourself. You could start off by brainstorming all the related topics you are interested in (sort of like you did in your question). Then take this list and start prioritizing. What are the topics you are most interested in? How much time do you realistically have to spend? Whittle it down to a list of a few books or resources that you hope to complete within the next few months.
• Set a concrete goal. This might simply flow from the plan you have made: "I will read these four books this summer". Or it could be a starting point for your learning that sets the direction you choose to take. "I will learn how X works." It could be a project, like "I will create a small working example of software that does Y".
• Use online learning resources. There are many free online courses on computer graphics and related topics. Alternatively, many college professors post their syllabi online, which you could simply use as a reading list.

If you are actually new to a topic then the papers on it are probably out of your reach.

When I want to open a truly new topic I would start with the lowest level textbook I can get. Perhaps I find that a first year undergrad textbook is not challenging enough to be interesting, but its worth checking each chapter to see if there is anything new. If there is new content then it will definitely be possible to understand without any prerequisites. Then I move on to a slightly higher level textbook, etc.

This should bring you smoothly up to the level of papers, and any periphery knowledge (from other subjects) needed will probably be presented at a level that is easy to access.

(full disclosure, I have only ever done this with topics in maths, perhaps it doesn't work well elsewhere)