Open source mechatronics software.
You Can Model in OpenModelica and Render in a Game Engine
Simulations of real machines controlled by a user interface can be simulated. Great way to prototype machines.
See paper - controlling a virtual excavator with an Arduino physical interface.
http://www.ep.liu.se/ecp/132/096/ecp17132879.pdf . FMU stands for Functional Mockup Unit
Imagine a village building video game where virtual builds of machines are actually done, using realistic components so that realistic machine behavior results. See OSE Game