[vtkusers] vtkAssembly : restore postion and rotation stored in quaterion ?

[David Gobbi]

Hi Umanga,

The RotateWXYZ() method expects an angle in degrees, rather than
radians.  Also  try calling SetPosition() after RotateWXYZ() instead
of before (I'm not 100% sure if that will work, but you should try it
both ways).

 - David


On Thu, Jan 12, 2012 at 7:45 PM, Ashika Umanga Umagiliya
<aumanga at biggjapan.com> wrote:
> Greetings all,
>
> In my application ,I want to store status of my actor (vtkAssembly
> consisting several vtkActors).
> I need to store the rotation as a quaternion.
>
> Here is the code snippet how I store the status :
>
> void captureAssemblyStatus()
> {
>
>  CaptureInfo capinfo;  //struct to keep the status
>  double m[3][3];
>  double quat[4];
>  double pos[3];
>
>  //get the rotation matrix in a 3x3 matrix
>  vtkMatrix4x4 *mat=assembly->GetMatrix(); //assembly is a vtkAssembly
>  for (int i=0; i<=2; i++)
>   for (int j=0; j<=2; j++)
>     m[j][i] = mat->GetElement(j,i);
>
>  //store the rotation in a quaterion
>  vtkMath::Matrix3x3ToQuaternion(m, quat);
>   assembly->GetPosition(pos);
>
>   capinfo.qw=quat[0]; //quaternion w
>   capinfo.qx=quat[1];; //quaternion x
>   capinfo.qy=quat[2];; //quaternion y
>   capinfo.qz=quat[3];; //quaternion z
>   capinfo.x=pos[0]; //postion x
>   capinfo.y=pos[1]; //postion y
>   capinfo.z=pos[2]; //postion z
>
> }
>
>
> And here's how  I am trying to restore the status :
>
> void restoreStatus(CaptureInfo &cap)
> {
>  double qw=cap.qw;
>  double qx=cap.qx;
>  double qy=cap.qy;
>  double qz=cap.qz;
>
>  //Restore the postion
>  assembly->SetPosition(cap.x,cap.y,cap.z);
>
>  //Restore the rotation
>  double scale=sqrt(qx*qx + qy*qy + qz*qz);
>  double angle=2*acos(qw);
>  double ax=qx/scale;
>  double ay=qy/scale;
>  double az=qz/scale;
>
>  assembly->RotateWXYZ(angle,ax,ay,az);
>
> this->qtWidget->update();
>
> }
>
>
> But this does work correct.
> Even when I commentout the rotation part,the position restore doesnt work well.
>
> What am I doing wrong here ?
>
> Thanks in advance