Alright here we go SDK scene viewer and previews are now gamma corrected · jMonkeyEngine/sdk@20b208b · GitHub
So basically, once you add gamma correction to JME, ALL frame buffers are in linear mode except the last one (the main frameBuffer, the one that writes to screen) that is in srgb mode. The thing is here the last framebuffer is the one written to the panel and idk how it’s done in your editor, but in th AwtPanel there is a parameter to set the frameBuffer to srgb.
Whatever you use for javaFX, there must be something similar, since you most certainly use a frameBuffer to write to an image.
You have to cal frameBuffer.setSrgb(true), and you’ll have a correct gamma corrected pipeline.