Hi All I have spent allot of time trying to resolve my problem but I could not find a solution. I posted my question on game programming forum but no body helped. may be they are scared from quaternions. I am using directx so the coordinate system is left handed where the positive z axis goes into the screen. I am trying to build a simple camera. I am given the up vector, the position of the camera and the target to look at. with this information in hand, it is very easy to build a left handed look at matrix, I already did that but this is not what I want. my scene nodes including cameras have their orientaions stored as quaternions. wheneve I need to animate a node I manipulate the orientaion quaternion then finally it gets converted into a world transform. this is working fine with me but I could not make it work in case of camera. the same way I need to manipulate the camera orientation quaternion and finally convert it to a view transform. sorry for the long explanation but I think it might help. here is what I did : the view transfom is the inverse of the transform needed to move the camera position to the origin and realign the camera look, up and right with the z, u and x axes //Set camera position m_relPos = camPos //up vector m_up.Normalize(); //Calculate look at vector //m_relPos below should be the absolute pos but here //I am assuming the camera has no parent m_look = m_target - m_relPos //Normalize the look vector m_look.Normalize(); //Quaternion to rotate the look to z core::Quaternion look2z; //Quaternion to rotate the up to y core::Quaternion up2y; //calculate look2z look2z = look2z.getRotationTo(m_look, core::Vector3::UNITZ); //calculate up2y up2y = up2y.getRotationTo(m_up, core::Vector3::UNITY); //Update camera orientation m_relOrient = look2z * up2y; so far the camera m_relPos and m_relOrient are there convert the m_relOrient to rotation matrix and set the translation to m_relPos and store it in m_relTransform //Calculate view transform as: m_view = m_relTransform.getInverse(); what is really confusing me is that I guess there is something tricky here. for example: if we look at the origin from the positions: camPos ==== (-10, 0, 0); ok (-10, 10, 0); ok (-10, 0, -10); ok (-10, 10, -10); view is shifted or rotated (0, 0, -10); ok (0, 10, -10); view is shifted or rotated (10, 0, -10); ok (10, 10, -10); view is shifted or rotated (10, 0, 0); ok (10, 10, 0); ok it does not work only in the cases where the y and z of the look vector are both non zero. I can not find an explanation for this. I am suspicious about the fact that direct x is a left handed system while the quaternion math assumes right handed system. sorry for the long message, I entended to do that to make things clear. any help is appreciated thanks again

thanks DrGUI for the code, actually I have no problem with that since I already have the code the finds the quaternion to rotate a vector to a vector. but there is something wrong in the way I rotate the look and up vectors.
regarding the dx quaternion class. thanks for the hint but I doubt it is gonna change something, I have a good quaternion class. I think my problem is in the login I am using. look at this statement: the view transform is basically the inverse of the transform needed to translate the camera position to the origin and re-orient its local coordinates with the world x , y and z. I am trying to implement that. rotate the look to -z and up to y but it does work in some cases and does not wrok in the other cases. there should be something stupid that I am not paying attention to since in the cases where it does not work I can see the objects I am looking to but there are not in the middle of the screen. the camera is like shifted or missoriented.