Lighting Theory: Radiometry and Photometry
Recent games have been heading towards Physically Based Rendering and this requires a solid understanding on lighting theory more than ever before. This time, I'm posting my note on Radiometry and Photometry . Radiometry Radiometry is basically ideas + mathematical tools to describe light propagation + reflection. Radiative Transfer is a study of transfer of radiant energy (which operates on geometric optics level - macroscopic properties of light suffice to describe how light interacts with objects much larger than light's wavelength). Four Radiometric Quantities : 1. Flux (Radiant Flux/Power) - total amount of energy passing through a surface or region of space per unit time (J/s or Watt). Total emission from light sources is generally described in terms of flux. 2. Irradiance (E) - area density of flux arriving at a surface (Watt/m2) Radiant Exitance (M) - area density of flux leaving a surface (Watt/m2) 3. Radiant Intensity (I) - flux density per solid an