Research On The Color Simulation And Storage In The Virtual Painting

Virtual clay modeling(virtual clay modeling, VCM) is a new CAD technology, virtual clay modeling system based on force feedback technology enables designers to complete the appearance innovative design of the product in a virtual environment, but lack of product surface decoration, so it is necessary to put virtual painting into the system, based on virtual clay modeling technology to further realize the function of surface decoration.The virtual painting is the combination of computer and art, simulating the effects of an work of art naturally and realisticly is one of the important target of virtual painting, and simulation of color is the key to simulating effects. So studying on how to realize the rich color changing art effects of mixture and superposition for multiple pigments is significant.This subject comes from National Natural Science Fund "The Study of Virtual Product Surface3D Painting Method based on Real-Time Force Feedback Technology" project(51175058), studies the color simulation and storage in virtual painting. According to the requirements of color simulation of the virtual painting system, analyzing the characteristics and usage of common pigment in the actual painting, elaborated the Pigment coloring mechanism which based on optics, studied Kubelka-Munk (K-M) theory which described pigment’s properties using the scattering coefficient (S) and absorption coefficient (K)and solved color changing of mixture, In the virtual painting, a new method of color simulation based on the Kubelka-Munk color optical theory is presented firstly. The primary idea includes: the absorption and scattering coefficients (K and S) for a pigment at R/G/B three color channels are calculated by giving the hiding power (c) of the pigment and the reflectance of "unit thickness" of the pigment over a black background (Rb) both at three color channels. Given K, S and effective thickness (d) for a pigment and the reflectance of substrate, the reflectance (R) of the pigment over the substrate are calculated. Then they can be transformed into color intensities (R, G, B), and the mixing color (RGB) of the several pigmented layers over rice paper background is determined. Secondly, a color storage method is introduced to access and display painting results in real time by storing the color (RGB) over rice paper background.Finally, the proposed methods are applied to the virtual painting system based on the force feedback technology,The different characteristics of vegetal pigments and mineral pigments in mixing process are simulated.