I’m trying to cut surfaces around my sub tool using dynamesh and (subtraction) insert sphere brush. When I remesh, I get the cuts I want but it closes the main barrel hole right in the center. Any ideas why? And how should I approach doing this?
Sometimes performing many cuts at a time can produce odd results. There’s a limit to the complexity of the subtraction operations. We could try to troubleshoot your process step by step, or see if you have anything odd about your geometry, but the easiest thing to do at this point would just be to re-cut the barrel hole after the sides have been done.
There are options in Preferences> Geometry for controlling how Dynamesh will close holes on open meshes, but that doesn’t appear to be your problem here.