Is it a good idea to join SIGGRAPH without a degree?
Students get a special rate when they join ACM and/or its SIGs (special interest groups). You get the Communications as part ACM membership. You can also join any of several special interest groups such as SIGGRAPH. There is some cost for that even for students. But you get their publications, either electronically (cheap) or in printed form (less cheap). There are, I think, special prices for conference attendance at the annual conference for members.
The special deals don't apply to non-students, of course. Most academics in CS are likely to be ACM members and those interested in graphics are likely SIGGRAPH members.
It probably isn't essential to do this, depending on how connected you want to be to that community over time. But the publications are interesting if you are interested in the topic, and the conference(s) are great for career building. SIGGraph is a huge event.
Some universities, however, have local &quot;chapters&quot; of ACM and they may have additional local activities for members.
ACM and SIG members can also subscribe to the ACM digital library which gives you access to just about everything ACM has published since some early date (and they are digitizing the old stuff). But a local university library can probably get you access to that as well, though they might require some affiliation with the university.