When using OptiFine 1.12.2, panorama backgrounds will not load and instead will be replaced with the tiled dirt background texture. Interestingly the overlay.png texture will still be present overtop.

To Reproduce
Steps to reproduce the behavior:
using forge 1.12.2

1. Install only FM and required mods
2. Install OptiFine
3. Open a layout which uses a panorama background
4. See error

Expected behavior
Panorama background displays normally

Basic Informations (please complete the following information):

• OS: Ubuntu 21.10
• FancyMenu 2.3.5
• Forge 14.23.5.2855
• Minecraft 1.12.2
• Active Mods: Optifine, FancyMenu, JustEnoughIDs, konkrete

Added it to the incompatibility list, thank you! :)

Update: this only happens when fast render is turned on. Probably not a bug, but worth mentioning on the incompatibilities page as other types of panorama work with fast render so it's unexpected.

But does it work without OF?
Because this can also happen if you're using wrong values in the panorama properties (FOV and angle). Please try to exactly replicate what you did, but without OF, and see if it works. Window size could be an important factor here.

Uh might have to reopen this one chief

It would appear the dirt background is some sort of eldritch rotating mask that applies over top of the panorama, but underneath the overlay. I found this out by going into windowed mode, which exposed the sides of the screen to be showing the pano animation:

These slanted areas rotate in and out of view, but the dirt texture stays static.

So I think this actually is a bug.

It starts getting weirder the more you squish it, too. These patches rotate in sync but in opposite directions.

Yes, it works perfectly without OF or if fast render is disabled in OF settings. The reason I say it's a bug is that my initial assumption was that fast render disables the panorama for speed, but it's obviously still rendering it so that can't be right.

Well, but disabling fast rendering fixes it, so it's a compatibility issue with OF, caused by fast rendering :D Disabling is a good workaround. I don't think that I will ever be able to fix this on my end. OF is just weird in too many cases and reverse-engineering the 2000 changes they do to the vanilla code is simply impossible. I'm really sorry, but if it really works without any issues when fast rendering is disabled, then I will close this for now. Thank you very much for the report and the great info about disabling fast rendering, will help me a lot in the future :)

Cool, you're welcome :3