Simulation And Rendering Of Dynamic Hairs

In the process of creating avater, researchers always ignore the element of hair. Realistic hair is an important component that makes characters look real. But the amount of hair is huge, which results in a speed bottleneck. Stiffness, stretched to deform, and dynamic effects are also needed to be taken account during hair simulation. All the problems above bring a big challenge for hair simulation and rendering.This thesis adopts the dynamic follow-the-leader method to achieve the balance between visual effect and speed in hair simulation. Firstly, we present a fast interpolation algorithm based on Gaussian kernel function, which can interpolate smooth hair fast, and increase the density of hair. Then, this thesis proposes a simple curly model. The offset function is used to alter positions along the hair strand and create curliness on the hair. To improve the dynamic effects, we use ArcBall algorithm to achieve the interaction between mouse and head model. Users can rotate the head through the mouse, and the hair follows the head at all times. Finally, this thesis proposes a wind model based on mathematics and physics, which can be used to simulate dynamic hair driven by wind in real time through controlling wind speed adjusted by wind factor. During hair simulation, Aixe Align Bounding Boxes(AABB) and bounding spheres are used to handle the collision between hair and head. Hair-hair interaction is handled with hybrid Eulerian/Lagrangian approach. We render and shade the hair by two shading models, Kajiya-kay and Marschner, in real time,and deep opacity maps algorithm is also used to generate hair self-shadowing. During hair rendering, geometry shader is used to change and subdivide the hair geometry, which can taper the hair fiber. To make the hair smoother, three points are interpolated between each segment of hair with Bezier curve.Through the above methods, we build a dynamic hair simulation system with good interaction based on fixed-function pipeline and programmable pipeline. The final experiments prove that our interpolation algorithm and wind model perform well in the dynamic hair simulation, and have good real time results as well.