Light scattering in translucent layers: angular distribution and internal reflections at flat interfaces

Optical characterization and appearance prediction of translucent materials is needed in several fields engineering such as computer graphics, dental restorations or 3D printing technologies. In the case strongly diffusing materials, flux transfer models like Kubelka-Munk model (2-flux) 4-flux have been successfully used to this aim for decades. However, they lead inaccurate color variations objects different thicknesses. Indeed, assume Lambertian fluxes at any depth within material particular bordering interfaces, fail internal reflectance penalizing accuracy optical parameter extraction. The paper investigate impact translucency on light angular distribution corresponding reflectances, by mean radiative equation, which describes more rigorously scattering propagation. It turns out that assumed be flat, far from being Lambertian, may vary a lot according layer’s thickness, refractive index, absorption coefficients. This work not only enables better understand layer but also invites revisit well-known Saunderson correction 2- 4- models.