Fig. 1. Light distribution model of a single light source at point O. (a) Luminance distribution model; (b) illuminance distribution model

Fig. 2. Illuminance distribution models under the combined action of point light sources S₁ and S₂ in a dark environment. (a) Illuminance distribution models for S₁ and S₂; (b) dark solid shape illustrates superposed illuminance model distribution due to S₁ and S₂; (c) light circle shows equivalent illuminance distribution of resultant vector component; (d) dark shape illustrates symmetric component of illumination distribution model

Fig. 3. Illustration of spherical harmonic basis components

Fig. 4. Measurement model. (a) A cubic meter inside a spherical light source; (b) a spherical probe with Lambertian surface inside a spherical light source; (c) a cylindrical probe inside a spherical light source

Fig. 5. Four illuminance models changes with luminescent solid angle under spherical light source