Hello !! I’m currently studying the fish anatomy ( zebra fish) and blender too ^^ and I was wondering how to replicate this clean cut in a mesh ? with the knife tool ? and I guess the proportional editing / and move tool ?
This is the betta fish model from Nenghuo
There are several ways to get that cut. Assuming you started by modeling the basic fish shape as a closed mesh including the fish head, you can get such an open seam with the “rip” tool, but it would also be possible with an extrude and deleting some faces where the cut should be.
Btw it looks like the topology here isnt without flaws, eg in the area I marked, so be careful not to replicate them.
