𝐗→P𝐱\mathbf{X} \xrightarrow[P]{} \mathbf{x} 𝐱\mathbf{x}: 2D position in camera plane
Image function: ψ(P(𝐗),t)=ψ¯(𝐗,t)\psi(P(\mathbf{X}),t)=\overline{\psi}(\mathbf{X},t) or ψ(𝐱,t)=ψ¯(P−1(𝐱),t)\psi(\mathbf{x},t)=\overline{\psi}(P^{-1}(\mathbf{x}),t)
The projection operator is non-linear – Perspective projection – Orthographic projection – More on this later
ψ¯(𝐗,t)\overline{\psi} (\mathbf{X},t) is Camera absorption function