[ODE] How to Build the Model?

[Roel van Dijk]

> can anybody tell be the center of
> gravit referencs to the local frame or global frame? and about the inertia
> tensor?
I believe that the mass's center of gravity is relative to the local frame. I 
think the inertia tensor is also relative the the local frame, but I'm not 
entirely sure.

>    2.when build the "body" ,there needs to set the "positon",the question
> is the same as ahead. Moreover, is it necessary to set the orientation of
> the body?
The position of the body is relative to the global frame.

>    3.when build the "joint",for example the hingerjoint,
> there needs to set the joint anchor and joint axis vector.do these
> parameter reference to local or global frame?
Global frame.

>    4.when using the function of getRotation(),it returns the R, from the
> forum,i learn that it must be transposed, is it true?
That depends on how you want to use it. Column major or row major? I think you 
can feed the matrix directly to OpenGL but DirectX needs a transposed matrix.

>    I have integrated ode into my project( we are using wtk as our rendering
> tool),but the result of the simulation is wrong.
What is wrong with the result from the simulation? Is it instable or 
inaccurate? Collisions not working?