The Research Of Real-time Rendering Technology On Character Skin

Nowadays,in movie industry,by using digital techniques to create all kinds of visual special effects, constantly produce many excellent movies;In video game industry,is also using computing graphics rendering techniques to create innumerable classic games. However, these two media each have shortages. Interactive movie, the brand-new media can compensate for their shortages which single storyline for movie and low quality visual effects for game rendering. It provides movie's lifelike effect and game's interactivity, multi narrative and multi ending. And one of the key techniques is real-time rendering.Meanwhile,this technique relate to different objects rendering, Especially emphasizing on real tactile sensation, such as the different materials of metal, brick and water. When deal with this kind of effects, just use textures to distinguish them before, lack of in-depth research on its visual effects.Among them,the character skin effect is the most complex part. This translucent material has always been an advanced topic in pre-render field. Scientists have many experiences and achievements on how to simulate 3S(Sub-Surface Scattering). But it's hard to apply to interactive Medias directly because of shortage: complex shader, large amount of calculation and low efficiency.How to approximate to simulate this kind of effect on characters in activity movies and real-time rendering with high efficient will be a significant job.In view of this, this paper through long term of game industry experiences, making large number of tests, comparisons and modification, simulate the character skin effect which close to movie quality and with acceptable efficiency.In this paper, the research focuses and main achievements of this thesis are as follow: Establish the workflow about the character details producing. Using normal map is the best way to balance the efficiency and final quality. Research how to achieve the optimized models base on 3d software. And achieve perfect normal maps according to reasonable polygon topology.Master some basic concepts of illumination models, and determine the implementation methods of character basic skin. Try and research the working principle of scientific expressions, multi vector expressions, texture sample expressions and texture coordinate expressionsThe paper through composite node expression nets, simulate the diffuse, multi-mask layer normal and specular effects. By comparison of different parameter settings set up a series of correct settings. And then apply to whole material net to get realistic basic skin shader.Discuss about the visual effects of Sub-Surface Scattering objects. Real know the effects of 3S through comparison of a variety of images which rendered by 3S techniques.Draw up 3 sets of scheme to simulate translucent effect of sub surface scatter from simplest to more realistic methods. They are Emissive algorithm, Fresnel algorithm and Transmission algorithm. Compare and modify the transmittance. Point out the shortage for each. The conclusion is: transmission algorithm can produce the effect which is very close to offline 3S rendering.By two reflection techniques (single image based reflection and cube map reflection) to simulate realistic eyeball. Analyzing the difference between eyeball effects and other parts, achieve the conclusion that the reflection effect is key factor.