quote:

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Original post by Sander
A very good article. I've been struggling with rotating vectors with quaternions a bit. I finally understands now. Thanks!

Now for the nitty gritty: I found two code bugs in your article. It's the same bug twice and their in the first two sample codes (the conjungate and normalize functions)

Both functions should be " void FunctionName" and not " quaternion FunctionName". Maybe it's just an error on the page and the "::" between them got eaten by IE, maybe not. Sorry if I sound picky.

Oh, and please do that 3rd person camera :-)

Sander Maréchal
[Lone Wolves Game Development][RoboBlast][Articles][GD Emporium][Webdesign][E-mail]

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void camera::RotateCamera(double Angle, double x, double y, double z)
{
  quaternion temp, quat_view, result;

  temp.x = x * sin(Angle/2);
  temp.y = y * sin(Angle/2);
  temp.z = z * sin(Angle/2);
  temp.w = cos(Angle/2);

  quat_view.x = look.x;
  quat_view.y = look.y;
  quat_view.z = look.z;
  quat_view.w = 0;

  result = mult(mult(temp, quat_view), conjugate(temp));

  look.x = result.x;
  look.y = result.y;
  look.z = result.z;
}

void camera::control()
{    
     vect MouseDirection;
     //middle
     int midx = screensize.x/2;
     int midy = screensize.y/2;
     
     static double xrot = 0.0;
     double maxAngle = 1;
     
     quaternion dlp;
     dlp.x = look.x - pos.x;
     dlp.y = look.y - pos.y;
     dlp.z = look.z - pos.z;
     
     
     if((pt.x == midx) && (pt.y == midy))
    return;
    

      
    MouseDirection.x = (midx - pt.x)/MouseSensitivity; 
    MouseDirection.y = (midy - pt.y)/MouseSensitivity;
    SetCursorPos(midx, midy);
      if(xrot > 1)
  {
    xrot = 1;
    return;
  }
  
     if(xrot < -1)
  {
    xrot = -1;
    return;
  }
  else
  {
    // get the axis to rotate around the x-axis. 
    quaternion Axis = CrossProduct(dlp, up);
    // To be able to use the quaternion conjugate, the axis to
    // rotate around must be normalized.
    Axis = normalize(Axis);

    // Rotate around the y axis
    RotateCamera(MouseDirection.y, Axis.x, Axis.y, Axis.z);
    // Rotate around the x axis
    RotateCamera(MouseDirection.x, 0, 1, 0);
  }
  
  
  gluLookAt(pos.x, pos.y, pos.z, look.x, look.y, look.z, up.x, up.y, up.z);
}