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Matlock's avatar
Matlock
Honored Guest
12 years ago

GetPredictedOrientation() causes shear on roll

Quatf hmdOrient = poculussensor->GetPredictedOrientation(); Matrix4f View = Matrix4f(hmdOrient); If you use this matrix to render, yaw, and pitch work as intended, but of you roll(twist) your head...
kojack's avatar
kojack
MVP
12 years ago
Check if the quaternion is unit length. A non unit length quaternion can do all kinds of freaky stuff (skewing and distorting), while a unit length one will be a simple rotation.

Hmm. Looking at the code, the oculus sdk converts a quaternion to a matrix using this code:
       return Matrix4f(float(ww + xx - yy - zz),  float(T(2) * (x*y - w*z)), float(T(2) * (x*z + w*y)),
                        float(T(2) * (x*y + w*z)), float(ww - xx + yy - zz),  float(T(2) * (y*z - w*x)),
                        float(T(2) * (x*z - w*y)), float(T(2) * (y*z + w*x)), float(ww - xx - yy + zz) );

But the standard formula for converting is:
1 - 2*qy2 - 2*qz2 	2*qx*qy - 2*qz*qw 	2*qx*qz + 2*qy*qw
2*qx*qy + 2*qz*qw 	1 - 2*qx2 - 2*qz2 	2*qy*qz - 2*qx*qw
2*qx*qz - 2*qy*qw 	2*qy*qz + 2*qx*qw 	1 - 2*qx2 - 2*qy2

Everything is the same except the main diagonal.