eye and up vectors from view matrix

assuming the following matrix layout:

m₁₁ m₂₁ m₃₁ m₄₁
m₁₂ m₂₂ m₃₂ m₄₂
m₁₃ m₂₃ m₃₃ m₄₃
m₁₄ m₂₄ m₃₄ m₄₄

You get the up vector from the view matrix like this:

up = (m₁₂, m₂₂, m₃₂)

For the position/eye vector you need the inverse view matrix and then it's
eye = (m₄₁, m₄₂, m₄₃)

mh but position != eye vector, isn't it? in my matrix class, translation is stored in m14, m24, m34. if the camera looks along the negative z-axis, then the up vector should be (0, 1, 0) and the view vector (0, 0, -1), right? with your suggestion, however, the view vector is (0, 0, 0).. any idea what's wrong?
thanks!


[Edited by - Vexator on June 15, 2008 3:06:32 PM]

No, eye = position of camera. What you talk of is the lookAt vector or the looking direction. The eye-vector (0,0,0) is the default camera position.

ok sry, so what i need then is the lookAt-vector.. how would i get that? m13, m23, m33?

[Edited by - Vexator on June 15, 2008 5:08:33 PM]

Using the layout I described earlier, yes!

Only problem is that most people say look-at and mean a point (position + view_direction). Getting just the direction from the matrix is simple (as above).