The Research And Implementation Of Real-time Shadow Algorithms In 3D Scene

As key technology of real-time rendering, real-time lighting and shading can add realism to the virtual scene, so this technology is widely used in 3D games, virtual training systems, and 3D GIS systems. A lot of algorithms about generating realistic soft shadow have been presented in recent years. Unfortunately, these algorithms have many disadvantages, such as unable to generating self-shadowing, restrictions of the type of occluding and shadow receiving shapes, disregarding shape and size of an area light and neglecting inner penumbra rendering or outer penumbra rendering. In order to solve these problems, we did a solid and systemic research on real-time lighting and shading technology based on the latest programmable graphics process unit (GPU) in this dissertation. The follows are main works of this dissertation:(1) By using the programmable feature of programmable graphics pipeline, we implemented per-vertex lighting model based on Gouraud shading model, and per-pixel lighting model based on Phong shading model. Compared with lighting model implemented on fixed functions pipelines, these two lighting models have more flexibility and realism.(2) We analyzed and compared current hard shadow generating algorithms, and in order to solve the bias problem about shadow maps algorithm, we present a novelty Adaptive Depth Bias Algorithm,which can set the depth bias according the 3D scenes easily. Compared with the traditional algorithms, our algorithm can analyses the characteristic of the 3D scenes and set a suitable depth bias.(3) Based on the analysis of the existing soft shadow algorithms, we presented a novelty inner-outer penumbra fins algorithm. This method developed Chan's smoothie soft shadow algorithm by building inner and outer penumbra fins in the silhouette of the objects and using the second depth shadow maps to control the generation of the inner penumbra. The algorithm inherits the features of shadow maps and shadow volume, and it could modify the size of the penumbra automatically according to the size of light source. The algorithm is implemented in the programmable graphics hardware and we accelerate it using the features of modern graphics hardware so we can offer a real-time performance on soft shadow.(4) Finally, this dissertation compared the inner-outer penumbra fins soft shadow algorithm with several traditional soft shadow algorithms in three aspects, the rendering...