Getting Started with 3D Printing, 2nd Edition

model is. Think of it this way: all 3D models define a

space that is either “outside” or “inside” the model,

like the outside or inside of a ball. If you were to fill

the inside of a manifold ball with water, no water

would come out. There would be no holes and no

place for the water to leak through.

A non-manifold model is the opposite. Water would

leak out of a non-manifold ball because there

are holes or missing data in the 3D model. Often

non-manifold models have large holes that are easy

to see. Sometimes, though, the 3D model may look

manifold but really is not. The sphere in Figure 13-9

looks manifold upon human visual inspection, bu