• Polarisation. Fresnel losses are averaged over polarisation at each surface. No polarisation state is carried between bounces.
• Birefringence and pleochroism. Every stone is traced with a single index. Birefringence is listed, not rendered, so moissanite’s doubling does not appear.
• Full spectral dispersion. The simulator uses three wavelengths and the census two, both at the exit facet only. The Brightness & Tilt Analysis and the Cut Grading Tool’s brilliance use none.
• Partial internal reflection in every measure except the simulator. Internal total reflection is lossless everywhere.
• Scattering and surface roughness. Facets are perfectly flat and polished; the simulator’s polish grades act on the finished image.
• The observer. Apart from a head-shadow cone, no body, camera or setting blocks the light. The analytical measures view from infinitely far away.
• Real stones. Every figure describes the design. A cut stone’s figures will differ with its make, its material and its setting.