how to fix a scan

Some tools :

Meshlab

http://www.meshlab.net/

 Smooth/Reconstruct                           Filter     → point set → surface reconstruction: poisson

→ Octree depth (start at 10)

                                                                 Layer     → Select Poisson mesh

→ Export selected layer as .obj

This will fill the holes in a nice way

Another usefull filter to emphasis simple geometry

Filters -> Remeshing, Simplification and Reconstrucion -> Quadratic Edge Collapse Decimation

Put a low number of faces

Meshmixer

http://www.meshmixer.com/

                                                           Import   → .obj does better than .stl

For a flat base                                       Edit      → Plane Cut (shadow part will be discarded)

To repair holes                                     Edit      → Close Cracks

To make solid                                       Edit      → Make Solid

Smooth/Highlight                                Tools     → brush (hold down shift to smooth, change size with cursor) → play with brush size, strength, etc.

Scale                                                 Analysis    → Units/Scale