Making a flat base

While inspecting the lion it becomes clear that all it is right now is a thin shell with huge gaps in it which is not very printable. What needs to be done is to clean up the mesh so it is closed, manifold, and has a flat bottom suitable for printing.

Note

A solid, printable mesh is closed, or watertight, and manifold.

Closed or watertight is an easy enough concept to get. In cartoons, the characters can blow bubbles of any size or shape they want, but if that bubble gets a single hole it pops. In the same way, the mesh should be one continuous surface no matter the twists and turns it takes.

Manifold is a mathematical term that in general terms can be confusing, but in specific turns for our purposes means that every edge sits between no more than two faces and no face intersects any other face. (If it's watertight as well, each edge will border exactly two faces.) If an edge is bordering three faces, then there is an unnecessary face in the model. Non-manifold meshes can...