so im working on a scroll and wanted to a add paper cut to the scroll, i did it by using the knife however when i turn back the subdiviosn modifier (i also have the solidify modifier) back the cut looks weird. is there any way to fix that?
Example of a mesh before Catmull-Clark subdivision:
Subdivision rounds the mesh:
Removing parts of the geometry interferes with the way it is rounded by the subdivision algorithm:
And so you could remove that part with a boolean (easier) or a mask modifier (harder since you need to predict how the modifier will move the vertices) after subdivision modifier...
If you don't like the way some paths get wibbly-wobbly like on the 3rd image, you can retopo your mesh to better represent the flow of the object, and add holding loops to limit the range of the modifier:
You can also do a lot with creases (ShiftE):