[ODE] Units confusion

Tanguy Fautre tanguy.fautre at spaceapplications.com
Wed May 18 13:47:02 MST 2005


Zulfiqar Malik wrote:
> The problem is with the units ode uses. Its mentioned in the 
> documentation that acceleration e.g. gravity uses m/s/s units. But other 
> units like mass and forces are not mentioned. Its really confusing me 
> because I cannot get the movement of my player to work correctly. I have 
> a world in which 1 unit ~ 2.089 cm and I need to get the movement of my 
> player and bots working in that world. But even after experimenting a 
> couple of days with different values I cannot get it right. Can someone 
> please explain the conversion from “ODE Units” to the standard “SI Units”.

AFAIK ODE is using the MKS system (Meters - Kilograms - Seconds). But I 
could be wrong.


> Another thing that gets me confused is friction. I am using capped 
> cylinder, as I have heard they are the most stable primitive in ode 
> (correct me if I am wrong). But it seems that the friction model never 
> affects it in anyway because no matter how slowly its moving, it never 
> stops! Am I doing something wrong or is it supposed to behave like this? 

ODE handles surface friction but not rolling friction.
Thus, in ODE, a rolling sphere or a cylinder will never stop because of 
friction.


Tanguy



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