G3 to G4
Refraction-Reflection

Step limitation

• Geant3
  Boundary between two optical media (specified by refractive index
  (dielectric/dielectric, dielectric/metal, dielectric/black medium)
  

• Geant4
  Adapted from Geant3
  

Final state

• Geant3
  Classical Maxwell formulae for reflection,refraction and total internal reflection depending on photon's wavelength, angle of incidence, polarisation,and refractive indices.
  Surface roughness: GLISUR model.
  

• Geant4
  Adapted from Geant3.
  Improved navigation near media boundaries - concept of logical and physical surface.
  Surface roughness: GLISUR model (alternative: UNIFIED model).