Man, I'm sorry for necroing this, but this problem is still happening, even after doing all the steps you have told me. I even tried on other Macs, newer and older, 2k to 5k, and my FPS never goes higher than 20.
EDIT : Snapshots will load now, but are still capped at 15 FPS.
Well, the mod still has the same problem. I'm going to try everything I can to fix this. It's worth noting that Powder Game uses 117 percent of my CPU. I'll post again if I find a solution.
HAPPY EDIT : Wow. I did it. I fixed it. And I fixed it by doing one of the weirdest things possible.
I have a video of what I did, and I might post it here later.
Here's a rundown.
I opened my Application Support file in my library and found a few things. I found an autorun.lua that attempted to set my FPS cap to a massive number. I deleted it, and the problem persisted. So, I did something that the app even explicitly asked me not to do. I went into the powder.pref and saw a little box at the top that was named "History" and it contained the autorun.lua files. It also had something that set my max FPS to 2. I don't think this is what caused my issue, but it's possible since I removed the commands and replaced them with setting my max FPS to 60, then 120, then 240. Afterward, I went down into my user settings and saw that my average FPS was 16. I changed it to 60, started my game, and, while the resolution was extremely bad, (low-resolution mode) I was getting 60 FPS! I disabled low-resolution mode, and, poof! 60 Frames per second. Strange. I don't know how changing something in the console history had such a big effect on my game, but I'm so happy that I stuck with trying to fix it and persevered until I did. I wonder why I made that autorun.lua to begin with, though.
Thank all of you moderators and admins for your support!
EDIT 2 : In addition to what I did above, I also disabled Large Screen mode, which helped A LOT. Fullscreen will work for my Mac, I suppose. There might be some problem with the scaling in Large Screen mode, too, but whatever I did definitely worked.
Wow! So why is my sugar-rocket not launching to Mars? Could u fix plz?? :D