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Dual quadric

Similarly, the dual concept exists for planes. A dual quadric is the locus of all planes ${\tt\Pi }$ satisfying a homogeneous quadratic equation:
{\tt\Pi}^\top {\bf Q}^* {\tt\Pi} = 0
\end{displaymath} (B17)

where ${\bf Q}^*$ is a $3 \times 3$ symmetric matrix only defined up to scale and thus also depends on nine independent parameters.

Marc Pollefeys 2002-11-22