Same here. My specs:
macOS High Sierra
Version 10.13.6
MacBook Pro (Retina, 13-inch, Mid 2014)
Processor 3 GHz Intel Core i7
Memory 16 GB 1600 MHz DDR3
Graphics Intel Iris 1536 MB
They rendered properly in the previous version. However, the last snapshot brought this issue.
Related to terrain rendering on a map, I experienced this issue: MC-179858 when the markers rendered properly in the previous version; but since this issue is fixed in the current snapshot the markers stop rendering properly.
I fixed the issue following the steps above. However, I had to (re)explore the area carrying my maps to (re)paint them.
@JellySquid and @gegy1000 patch r3 improved my fps and my experience! You've saved my weekend. Thank you! 🙂
I can totally picture developers at Mojang looking away from this critical issue when it popped up on a Friday evening when they were about to close their computers and go home for the weekend. 😃