My task is to import a closed mesh into Blender, apply Bisect with the fill option, with the desired result being that the new body would also be a complete mesh.
However, the result I get has the bisect face filled with "grey", but no mesh. And an STL exported from that is similarly missing triangles in that area.
Example: Starting STL, a cylindrical cup, imported into Blender:
After applying the bisect tool along a horizontal line (ie: a horizontal plane):
As can be seen, the face that was cut has no triangles. And if exported to STL, that area is missing, with the overall shape not being closed.
Have I missed some option in bisect that properly fills in the mesh? Is there some subsequent step that's needed?