Validation of a Single-Image Inverse Rendering Setup for Optical Property Estimation in Turbid Materials

This work presents an experimental validation of a physics-based inverse rendering method for determining the reduced scattering and absorption coefficients of turbid materials in arbitrary shape from a single image per wavelength. Based on our previously published theoretical inverse rendering framework, we constructed and experimentally characterised a wavelength-selective measurement setup to realise and validate the method under real acquisition conditions. By accurately modelling the spectral behaviour and angle-dependent transmission of the employed bandpass filters, we ensured a close correspondence between captured and simulated reflectance. The method was evaluated on three silicone materials, beginning with simple cube geometries and later extending to a complex Einstein bust. Relative to integrating-sphere reference data, the recovered optical properties exhibit maximum absolute errors of approximately 4–10% for reduced scattering and 5–10% for absorption for the cubes, and 16–19% and 16–22%, respectively, for the bust. Forward renderings based on the recovered coefficients achieve CIE ΔE2000 values below 1 for the cube and below 2 for the complex geometry when compared with photographs. Additionally, we demonstrated that the approach can be applied using a common commercially available RGB camera, recovering optical parameters from each RGB channel, albeit with increased errors due to the camera’s broad spectral channels. Overall, our method enables the recovery of optical properties and the creation of accurate digital twins for objects of arbitrary shape using comparatively simple hardware, including common commercially available RGB cameras. This broadens its applicability to practical scenarios such as process monitoring and digital twinning when appearance, rather than precise material parameters, is the primary focus.