Initial quaternion from basis.

2014-03-01T01:50:34+00:00

Hi all,
A bit novice question, please excuse me if this is covered some place, did not find it.
I have an oriented bounding box that I am trying to derive a rigid body from. I know its center and its three axis. I followed bullet API/demos but seems to have problems with the initial quaternion orientation. What I do is setup the rotation matrix with the three ortho-normal vectors. Take transpose to get the inverse of rotation. Then call getRotation() to get back the quaternion representing the rotation matrix. However the quaternion is not what i expect. Using the first of the matrix basis vectors, and rotating it by the quaternion, I would expect to end up in (1,0,0) yet, thats not the case. Anything I am doing completely wrong? Thank you!

Here is an example:

Code:

v1.setValue(0.94085854,-0.21149139,0.26468223);v2.setValue(-0.28753003,-0.085231327,0.95397180);v3.setValue(0.17919759,0.97365654,0.14100073);btMatrix3x3 mtx(v1.getX(),v1.getY(), v1.getZ(),v2.getX(),v2.getY(), v2.getZ(),v3.getX(),v3.getY(), v3.getZ());mtx = mtx.transpose();btQuaternion rot;mtx.getRotation(rot);rot.normalize();btQuaternion invrot;invrot = rot.inverse();btQuaternion point(v1.getX(),v1.getY(),v1.getZ(),0);point = rot*point*invrot; //Result is point = (0.92, -0.13, 0.34)

Statistics: Posted by nipo — Sat Mar 01, 2014 1:50 am

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Initial quaternion from basis.