3D print devices and services

[Fonte Boa]

Thanks, Micheus:
according the first link you posted, the minimum wall thickness to a printer that is able to build 4mm walls should be the double: 8mm.
But my doubt is: how does the printer execute the model infill? Is this determined by the software that controls the device or user has to indicate this at the moment he builds the piece? (that is why i asked about Blender support tools for 3d printing?
For example, the Yoda model in the video i posted: why was it being printed that way and not full solid?