# how to calculate the whole body's rotation angle,use what joints

• ### Question

• i can calculate the rotations of hands,legs and neck very well ,but where i use left hip and right hip to calculate the whole body's rotation ,the result is not not good.

transform skeleton coordinates to the player space coordinates,then
vector3 v = lefthip - righthip
vector3 vRefer(1,0,0)
vRefer --rot-->v
the result rot is not good ,i output v find out that the y and z component of v are not zeros ,that's the problem,then how can i get the whole body's rotation?

Monday, December 5, 2011 6:26 AM

### All replies

• Hi Justin!

Try to calculate the rotation angle just using shoulders information.

You should find a vector with 0 degrees between shoulders ( vec_0_shoulders ), that's set by a vector defined from one shoulder ( left ) to the other ( right ) but this other one with same Z value as left one.So this will be the zero degree vector between shoulders.

Then the angle calculation will have sense because "real" (from left to right vector shoulder) and "vec_0_shoulders" vectors are in touch and are defining a right coordinate system to find such angle.

hope this help
• Proposed as answer by Tuesday, April 24, 2012 11:55 AM
Sunday, December 11, 2011 11:32 AM