Light Sources

• Emittance Spectrum (color)
• Geometry (position and direction)
• Directional Attenuation

Surface Properties

• Reflectance Spectrum (color)
• Geometry (position, orientation, and micro-structure)
• Absorption

Simplifications used by most computer graphics systems:

• Only the direct illumination from the emitters to the reflectors of the scene
• Ignore the geometry of light emitters, and consider only the geometry of reflectors