Update: this bug has been fixed – see here for details.
For X-Plane users with an AMD graphics* card on Windows or Linux: there appears to be a bug in the 13.11 drivers** that cause corruption in HDR mode; the symptoms are square artifacts of missing clouds and missing windshield in aircraft.
If you can run the 13.9 drivers, stick with those; if you have one of the new Rx 290 cards and you must use newer drivers, turn HDR off for now.
These bugs are Win/Lin only – the Mac AMD drivers don’t have this problem.
* AMD seems to have fully rebranded ATI’s GPUs at this point, so I guess I should get used to writing ‘AMD Radeon’.
** The bug could very well be in our code, but since the code worked on old ATI drivers and a number of other driver stacks, it may very well be a regression in the driver itself. We won’t know until it’s fixed. And even then, maybe we won’t know.