The site traces light in four ways. They answer different questions, so their numbers are not interchangeable. The T73 round brilliant in diamond, for example, reads 93 for brilliance on the Cut Performance Wheel and 54% in the Cut Grading Tool: the first counts the share of near-vertical light returned, the second the energy returned from an evenly lit dome, head shadow included.
| Simulator | Brightness & Tilt | Cut Grading Tool brilliance | Performance Wheel | |
|---|---|---|---|---|
| Rays | Per pixel, perspective, up to 64 samples | 132 × 132 grid, orthographic | 84 × 84 grid, orthographic | 3,200 seeded rays |
| Lighting | A lit room, ten scenes | Dome: ISO, COS or SC2 | ISO dome | Near-vertical beam, 6.9° cone |
| Head shadow | 6° to 10.5°, soft edge | 0° to 30°, default 10° | 23° | None |
| Fresnel | Full, unpolarised | Schlick, crown and exit | Schlick, crown and exit | None |
| Dispersion | Three wavelengths at exit | None | None | Two indices at exit |
| Internal bounces | 14 | 12 | 12 | 12 |
| Tilt | Any view you turn to | −30° to 30° | Mean of −30° to 30° | 0° and 20° |
All four treat total internal reflection as lossless, and none carries polarisation from one bounce to the next.