I was just sculpting a rock object in object mode, when all of a sudden, parts of it just turned purple. I don't think I pressed anything I shouldn't have. I don't know if this is normal of not, but does anyone know how to fix this?
In Sculpt mode, Face Sets allows you to create separate areas, a little bit like the Mask except you can create as many face sets as you want and you won't have to mask and unmask to switch from a face set to another, when you'll sculpt on a face set it will only affect this face set until you release the left click and click on another face set.
To paint your face sets you need to press left click. Release and left click again to create a new face set, Ctrl and left click on a face set to extend it, Shift left click to smooth the boundaries. In the Face Sets menu > Init Face Sets you can choose another way to create face sets (for example By UV Seams):
Once you've painted, choose your sculpt brush and enable the Face Sets options:
It looks like once you've painted your face sets you can't enable Dyntopo without deleting the face sets, Dyntopo creates new geometry so it makes sense.
How To Remove Face Sets
To remove/reset all
Face Sets, you can navigate to the top left corner of your viewport and click the
Face Sets button.
From here, click
Face Set From Visible to reset the entire mesh back to the default grey.
Alternatively, you can go to the top left corner and click on
Viewport Overlays. Then at the very bottom, toggle off
Face Set visibility.