Visible volume buffer for efficient hair expression and shadow generation

Much research has been conducted on hair modeling and hair rendering with considerable success. However, the immense number of hair strands means that memory and CPU time requirements are very severe. To reduce the memory and the time needed for hair modeling and rendering, a visible volume buffer is proposed. Instead of using thousands of thin hairs, the memory usage and hair modeling time can be reduced by using coarse background hairs and fine surface hairs. The background hairs can be constructed by using thick hairs. To improve the look of the hair model, the background hair near the surface is broken down into numerous thin hairs and rendered. The visible volume buffer is used to determine the surface hairs. The rendering time of the background and surface hairs is found to be faster than the conventional hair model by a factor of more than four with little lost in image quality. The visible volume buffer is also used to produce shadows for the hair model.