Moving towards Smart Manufacturing is a key challenge for the 4.0 Industry. This involves using digitized processes and technologies to enable significant adaptability and optimize the performance of processes and products. In this context, the control of the functional properties of surfaces, and particularly of the surface appearance, constitutes an important lever of added value. Many scientific and technological challenges are associated with this issue. The objective is, by quantifying the visual properties of manufactured surfaces at a roughness scale, to objectify a subjective, unconscious and complex process of sensory perception that integrates a wide range of previous representations. The approach proposed in the RTI4.0 project consists in implementing a measurement of the angular and spectral component of the re?ectance of surfaces according to the principle of the RTI technique (Reflectance transformation Imaging). The information obtained is multidimensional, allowing to estimate both apperance descriptors associated with the distribution of measured local luminances, but also geometric descriptors (altitudes, slopes and directional curvatures) through the estimation of stereo-photometric models. The challenges associated with this approach are numerous and multifactorial. The research actions envisaged mainly concern, on the instrumental level, the development of new RTI acquisition approaches (multimodal, adaptive, multiscale), and on the methodological level, the development of methods for the analysis of the properties of surface states allowing the implementation of a functional control of the appearance of manufactured surfaces.