[ODE] [Documentation] Pictures for friction

[Kévin Drapel]

Hello all,

While reading the ODE documentation, I have seen it was missing some good pics
to explain the friction concept. I rendered two of them which hopefully should
clarify these physical properties. I tried to reproduce a rendering similar to
the pics already present in the documentation : 

http://dake.calodox.org/ode_sliding.png
http://dake.calodox.org/ode_nosliding.png

Regards,

Kévin Drapel
kevin.drapel at epfl.ch
http://in1www.epfl.ch/~drapel