3D folks, I'm trying to find a good formal definition of "manifold" and "watertight" in relation to meshes.
Most definitions say something like "every edge is connected to exactly two faces", but that would imply that an inside-out mesh, a self-intersecting mesh, or a pair of triangles connected back-to-back (with zero volume) would also be manifold.
Is there a definition somewhere that covers these cases? And what is the difference between "watertight" and "manifold", or are they synonyms?
@nicklockwood In 3d printing, they’re usually synonyms. Self-intersecting or overlapping faces would make a model non-manifold.
https://www.instructables.com/Non-manifolds-Your-Worst-3D-Printing-Nightmare/
Non-manifolds: Your Worst 3D Printing Nightmare: Objective: Learn what manifolds are, how they affect 3D printing, and how to recognize what type of non-manifold problem may occur. To learn how to fix non-manifolds see: Manual Methods of Fixing Non-manifolds Automatic Methods of Fixing Non-manif…
Nick Lockwood
Craig Siemens