3D Mesh & Geometry Glossary
Standardized engineering definitions for 3D printing defects, mesh topology errors, slicer warnings (Bambu Studio, Cura, PrusaSlicer), and repair mechanisms.
Non-manifold edge
A non-manifold edge is an edge in a 3D mesh that is not shared by exactly two faces. It either borders a hole (one face), joins three or more faces (a T-junction or internal wall), or sits on top of another edge. Because the mesh no longer encloses a clear inside and outside, slicers can't compute solid walls — so they warn you, auto-repair, or refuse the file.
Watertight mesh
A watertight mesh (also known as a closed 2-manifold surface) is a 3D digital model whose outer polygonal surface completely encloses a continuous, solid volume without any holes, open seams, self-intersecting faces, or inverted normals. If you poured water inside the model, none would leak out. Slicers require a watertight mesh to distinguish solid interior infill from empty outside space.
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