Using getDirectionCosines

[Moe Curtin]

Could anyone please tell me in what order the values are returned when using getDirectionCosines and what they correspond to. I'm having trouble trying to figure it out, thanks!

[Ayman Habib]

Moe,

SimbodyEngine::getDirectionCosines(state,B,mtx)
Extracts from the state cache the spatial orientation R_GB of body B's body frame x, y, and z axes expressed in the Ground frame, as the Rotation matrix R_GB returned in mtx[3][3].

The sense of this rotation matrix is such that if you have a vector v fixed on body B, represented by the vector v_B expressed in the B frame, then v_G=R_GB*v_B where v_G is the same vector but re-expressed in the Ground frame.

This matrix can be later converted to BodyFixedXYZ Euler angles using the call to SimbodyEngine::convertDirectionCosinesToAngles

Hope this helps,
-Ayman

[Moe Curtin]

Thanks Ayman, that worked great!