don't attempt to normalize the rotation vector
indeed, by construction of the rotation matrix, it is
guaranteed to have a length of 1.
moreover, the normalization code was missing a square-root,
fortunatelly, since the length is 1, this didn't cause any
damage (since sqrt(1) = 1).
Change-Id: I9facd668caaf5bb3bfccb139ab872f2bb2066365
diff --git a/services/sensorservice/RotationVectorSensor.cpp b/services/sensorservice/RotationVectorSensor.cpp
index 6f4b8be..eecf260 100644
--- a/services/sensorservice/RotationVectorSensor.cpp
+++ b/services/sensorservice/RotationVectorSensor.cpp
@@ -114,10 +114,12 @@
float qx = sqrtf( clamp( Hx - My - Az + 1) * 0.25f );
float qy = sqrtf( clamp(-Hx + My - Az + 1) * 0.25f );
float qz = sqrtf( clamp(-Hx - My + Az + 1) * 0.25f );
- const float n = 1.0f / (qw*qw + qx*qx + qy*qy + qz*qz);
- qx = copysignf(qx, Ay - Mz) * n;
- qy = copysignf(qy, Hz - Ax) * n;
- qz = copysignf(qz, Mx - Hy) * n;
+ qx = copysignf(qx, Ay - Mz);
+ qy = copysignf(qy, Hz - Ax);
+ qz = copysignf(qz, Mx - Hy);
+
+ // this quaternion is guaranteed to be normalized, by construction
+ // of the rotation matrix.
*outEvent = event;
outEvent->data[0] = qx;
