# Camera rotation using quaternions

How do I specify the rotation of a camera using quaternions about an axis at a specified angle. I know how to rotate about individual axis, but what if I wanted the camera to rotate about all three i:e: u,v and n axis about the eye.
I am programming in C++ using OpenGL.

Thanks.
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Commented:
Hi,

I wish I could claim that I completely understood quaternions. What I had to do was keep up with the values (in degrees) of the heading (u), pitch (v), and roll (n) of the camera.  Then I created a quaternion from each of these angles and used them to figure out the view and driection of the camera:

//quaternions that represent rotation
m_qPitch.CreateFromAxisAngle(1.0f, 0.0f, 0.0f, m_PitchDegrees);
m_qRoll.CreateFromAxisAngle(0.0f, 0.0f, 1.0f, m_RollDegrees);

//combine pitch and heading and roll and put into quaternion q
q = m_qPitch * m_qHeading * m_qRoll;
q.CreateMatrix(Matrix);

// set our new perspective
glMultMatrixf(Matrix);

//get the y coord for our direction from the pitch quaternion
m_qPitch.CreateMatrix(Matrix);
m_qDirection.y = Matrix[9];
ypitch = Matrix[9];

//combine heading and pitch rotations to get the x and z coords for our direction
q = m_qHeading * m_qPitch;
q.CreateMatrix(Matrix);
m_qDirection.x = Matrix[8];
m_qDirection.z = Matrix[10];

For a better explanation than I can offer check this link: http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=Quaternion_Camera_Class

I hope that helps you more than hinders you:-)
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Commented:
deol_bhaji - Did jadecc answer your question? Do you need more or different information?

-bcl
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Author Commented:
Thank you Jadecc. The link you sent was quite helpful. I guess I need to study a bit more on quaternions first.
deol_bhaji.
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