So I've been sculpting a model, but I didn't really like the face too much so I duplicated the head geometry and worked on changing it. Afterwards I duplicated a new body and bridged the head edge loops to the body and fixed the area. Both are sculpted with dyntopo. Now after them being merged when I enter sculpt mode I get very bad FPS when navigating the viewport. If I zoom out and back in it is fine. If I use the undo or change my brush it gets low fps until I zoom out again. There are no modifiers on the mesh.
I also attempted loading the model into a new blend file the issue persists.
If I attempt to sculpt on the original body it works fine.
Any idea what is going on?
I wonder what your face count has become? Is it becoming too much for your computer?
Tip for narrowing down the issue (might not solve it):
What happens if you try applying a remiss of the sculpt (ctrl+r hotkey or look at the remesh tool in the header on the sculpt workspace in blender 2.8)? I would make a copy of your file and give that a go. You can turn the remesh resolution to something really high.
I heard a comment about sculpt mode bogging down under certain scenarios in theFundamentals of Sculpting video and I believe @theluthier mentioned that the remesh simplifies the sculpt in a way and does a kind-of "reset" when it gets cumbersome.
Shawn is right, you can use the remesh operation (CTRL + R in sculpt mode) as a means to "reset" the mesh to a desired, uniform geometry. The only problem with remesh is that it can blur your details. Whenever I use dyntopo for sculpting, I like to use the Decimate modifier to decrease my sculpt's polycount while maintaining the detail. Here's an example of that technique.