Interactive rendering of optical effects in wet hair

Visually, wet hair is easily distinguishable from dry hair because of the increased highlights and intense darkening displayed by them. It is therefore essential for realism to capture these characteristics under certain real world conditions. In this regard we propose a model for rendering wet hair at interactive rates. We start by analyzing the physical aspect behind this special effect in hair and then present a model for incorporating the variations in visual appearance of the hair due to presence of water. For simulating the increased specularity because of the water layer on hair, we present a parameter controlled Gaussian-based model. To simulate darkening in hair, for outer hair we consider total internal reflection at water-hair interface as dominant and propose a probabilistic approach to determine the amount of light absorbed. For inner hair, we consider that increase in opacity due to water results in stronger self-shadow and propose a model that updates the opacities based on water content and accumulates them to calculate the self-shadow term. By preprocessing and optimising our algorithm both for the self-shadow in dry hair and the special effects due to water presence, we can get visually pleasing results at interactive rates. Furthermore, the model is highly versatile and can easily be adaptable to other liquids and hair styling products.