Radiometry
$线性相机\Rightarrow {\rm RGB} \propto {\rm Enery [J]}$
$固定曝光时间\Rightarrow {\rm Energy[J]} \propto {\rm Flux[W]}$
$固定传感器大小\Rightarrow {\rm Flux[W]} \propto {\rm Radiosity[W/m^2]}$
$针孔相机模型\Rightarrow {\rm Radiosity[W/m^2]} \propto {\rm Radiance[W/(m^2\cdot sr)]}$
$色块反射\Rightarrow{\rm Radiance[W/(m^2\cdot sr)]} = f_{\rm brdf} \cdot {\rm Irradiance[W/m^2]}$
$色块接收光照\Rightarrow{\rm Irradiance[W/m^2]} = \int{\rm Radiance[W/(m^2\cdot sr)] \cdot d\omega[sr]\cdot cos\beta}=\sum{\rm Radiance[W/(m^2\cdot sr)] \cdot \Delta\omega[sr]\cdot cos\beta}$
$面光源\Rightarrow{\rm Radiance[W/(m^2\cdot sr)]}={\rm Intensity[W/sr]}\cdot{\rm Attenuation[1/m^2]}\cdot {\rm cos\alpha}$
${\rm Factor[1/m^2] = Attenuation[1/m^2]\cdot cos\alpha\cdot cos\beta},f_{\rm brdf}\propto {\rm RGB_{gt}}$
${\rm k_R[m^2\cdot sr/W]}\cdot{\rm Intensity[W/sr]}\cdot{\rm Factor[1/m^2]}\cdot {\rm R_{gt}}={\rm R}$
${\rm k_G[m^2\cdot sr/W]}\cdot{\rm Intensity[W/sr]}\cdot{\rm Factor[1/m^2]}\cdot {\rm G_{gt}}={\rm G}$
${\rm k_B[m^2\cdot sr/W]}\cdot{\rm Intensity[W/sr]}\cdot{\rm Factor[1/m^2]}\cdot {\rm B_{gt}}={\rm B}$