I've encountered recurring (recursive?) frustration in the process of retopologizing one of my meshes (very new to retopo, new to modelling & blender).
After eliminating several artifacts caused by mirror modifier I'm left with what appears to be a cleaner mesh:
However, the moment I subdivide this mesh these strange warped faces appear surrounding two problem vertices. [This is the same area where invisible faces and duplicated edges were caused by a mirror modifier. I believe this was the cause based on research, not knowledge.]
I've eliminated the earlier problems while maintaining the form through deleting the mirrored mesh, and careful replacement of edges and faces. I'm going to try fixing these two with cursor snapping but I'm having problems with the knife tool not agreeing to cut every new face that I'm attempting to cover them with in the way that it usually works for me. I'm not sure if this is related.
I put in a new face (8-gon) that covers all four problem faces with the problem vertex at the centre.
Delete problem topo by deleting vertex
Knife Cut to rebuild the interrupted loop via vert to its opposite neighbour vert across the square 8-gon to make 2 rectangular 6-gons.
Knife Cut to rebuild the second interrupted loop to make 4 quads but...
Issue: The moment I confirm to bisect the successful first cut with the second cut the result becomes a chaotic hole with folded faces (similar to the subdivided holes) that actually extends beyond the boundary of the new face into surrounding faces.
-eliminated loose topo and merged all the verts (by distance and at centre--making sure I was x-raying to select all of them--if dupes even existed)
-looked at the mesh in X-ray in Object mode and eliminated/replaced the highlighted dupe edges and faces in Edit Mode (what I thought was the mirror issue)
-retopology was exported to Cozy Blanket (tablet app) and reimported into blender for final clean up
-100% quads otherwise
Note: Before I replacing the dupe edges, I wasn't able to select the entire edge when double clicking. I assumed this would cause an obstacle to subdivision by an interrupted edge flow. But that's just me trying to put together what I know about topology. In the current mesh, I can double click and select the entire edge in both directions across the surface through these problem verts. Because of all of this, I believe the problem is (now, at least) in these two vertices
Very frustrated with this so I apologize for the length. This is probably my fifth or sixth full retopo attempt at this mesh (learning something new every time). I honestly thought I saw the checkered flag on this lap...
I will try deleting and cursor snapping new verts to the old one's location to fix this, but the length of time I've devoted to troubleshooting this so far leads me to believe that I've overlooked something and made rookie mistakes with knock-on effects that are showing up now in later workflow.
Does anyone know what mistake I've made here causing issue with these vertices and folding faces?
I appreciate you taking the time to consider this.