I see...that's because the getRotation()-method from SimpleVector actually is a lookAt()-implementation. It ensures that you "look at" some point in space but it doesn't make any assumptions about the rotation around the lookAt-axis. If you have two vectors, i.e. a direction vector and an up vector, you could do something like setOrientation in Camera:
public void setOrientation(SimpleVector dir, SimpleVector up )
{
// Code taken from paulcode's thread...only slightly modified.
SimpleVector right = up.calcCross(dir).normalize();
up=up.normalize();
dir=dir.normalize();
Matrix m = this.backMatrix;
m.set( 0, 0, right.x );
m.set( 1, 0, right.y );
m.set( 2, 0, right.z );
m.set( 3, 0, 0.0f );
m.set( 0, 1, up.x );
m.set( 1, 1, up.y );
m.set( 2, 1, up.z );
m.set( 3, 1, 0.0f );
m.set( 0, 2, dir.x );
m.set( 1, 2, dir.y );
m.set( 2, 2, dir.z );
m.set( 3, 2, 0.0f );
m.set( 0, 3, 0.0f );
m.set( 1, 3, 0.0f );
m.set( 2, 3, 0.0f );
m.set( 3, 3, 1.0f );
}
Is that an option in this case?