Failed my BEng dissertation in a computer/electronics related field twice, how do I move forward?
Your first and main source for help and advice on this should be your supervisor.
Working in industry I went through a high stress phase when I tended to cry during meetings with my boss. He was a very courteous person, and ignored my crying except for moving a box of tissues next to where I was sitting. Depending on your supervisor, you may need to bring your own tissues, but that is no reason to cut yourself off from essential help and advice.
Your supervisor knows what is expected for your dissertation. It is not something you should go off and study by yourself. Your supervisor should also be able to help you with where to go from here in terms of getting an extension and modifying your project if that is the best thing to do.
As for not having anything to say to him, &quot;I am stuck, and will not be able to hand anything in on the current schedule&quot; is something you should tell him as soon as possible - a few weeks ago would have been better than today, but today is much better than tomorrow.
In addition to a PhD in computer science I have over 30 years computer industry experience. I would plan and expect to spend a week or so learning my way round OpenGL if I needed it. Needing a few days to understand a tutorial, especially as you probably have less experience learning programming languages and libraries, does not seem like a very serious problem to me.
If you are using a current version of OpenGL with a ten-year-old tutorial that may be part of the problem. The tutorial and the OpenGL version you are using may not be compatible. In general, if a tutorial or book is not working for you, try a different one - there are plenty to choose from. Also, once the tutorial tells you what features you need to use, read the reference documentation on those features.
Given that you have medication for panic attacks, you may be able to use that issue to get extra time and help from your university's disability services. If you have not already done so, discuss your project difficulties with whoever is treating you for the panic attacks.