Capture and Simulation of Fluorescence in Fabrics Estimating and simulating fluorescent appearance in fabrics using LEDs and an RGB camera.

Abstract

In textiles, fluorophores (fluorescent molecules) are mixed with dyes to help achieve exceptionally vivid colours. Fluorophores help achieve such bright colours by absorbing light with a short wavelength (such as hard to see ultra-violet) and re-emit light with a longer wavelength (such as a blue, orange or red). The challenge when simulating fluorescence is that it places demands on the rendering-system (the system that simulates light interactions with the materials). An additional challenge is that methods to capture this fluorescent behaviour require specialised laboratory equipment. In this thesis, experiments are presented that aim to study if the multiple levels of structure in fabrics introduce any angular dependence of the fluorescence. The results suggest that in fluorescent yarns and fabrics there is no significant angular dependence. This result indicates that fluorescence can be captured from a flat sample from any distance, and that yarn-level resolution is not required in this regard. Using those conclusions a practical capture setup for fluorescence in fabrics is proposed. The method uses nine narrow-band LEDs, a consumer camera and an image analysis procedure that estimates the wavelengths of the detected light through numerical optimisation to give a re-radiance matrix. This matrix describes the fluorescent material’s spectral response to wavelengths of incomming light. The results using this capture setup are compared against raw data measured with a spectrometer. The results show agreement. Finally, matrices acquired from the capture setup are used to generate computer generated images of the materials under different illuminations. These images are compared to photographs of the same scenes.