[ODE] unit of masses, sizes - LCP internal error

[Matthias Baas]

Ramona Koch wrote:
> I've got a very simple question. Which mass unit is expected by  
> dBodySetMass? Should I use gramme or kilogram or something else? For 
> the  sizes I use meter, but maybe its better to use centimeter.
> 
> Which units are the best working one?

This has already been asked a lot of times. But surprisingly, it's not 
in the FAQ. I just wanted to add it to the Wiki, but the page is 
read-only (even after I tried to log in)... I wanted to add the 
following item to the "Using ODE" section in the FAQ, can anybody with 
write access please add it?


Q: What mass, length and time units do I have to use?

A: ODE does not make any assumptions about units, it just computes 
solutions to mathematical equations. This means you can choose whatever 
units you like. But be consistent! If you choose meter, kg and seconds 
as units, the units of velocity, force, etc. are also determined (i.e. 
m/s, kg*m/s^2 = N, etc.).
Also check out the section "How To Make Good Simulations" in the ODE 
manual, especially the last point that contains the "keep lengths and 
masses around 1" advice.


- Matthias -