I have a 3 x 4 projection matrix $P$ given that calculates a homogeneous 2-Vector ${\bf i}=(u,v,w)^T$ on some screen (e.g.) from a homogeneous 3-Vector ${\bf x}=(x,y,z,w)^T$ in world space by $P \cdot {\bf x} = {\bf i}$. 


How can I calculate the position of the camera in world space from that? 



Calculate camera position from 3x4 projection matrix
Sorry for answering my own question, but just now a colleague told me the solution and I want to share it - maybe it is of some use for anybody else some day.


1. Separate $P$ into a 3x3 matrix $P'$
(including the first three columns)
and a vector $\bf F'$ (the last
column).
2. Invert $P'$
3. The projection
reference point (i.e., the 'camera')
is then ${\bf F}=P'^{-1} \cdot {\bf F'} $.


