Research On Rendering Specular Highlight On The Water Surfaces

The scene of light on the water surfaces is increasing widely used in films,simulations and games. The photographic images are generated by ray tracingalgorithm, saving expensive equipment and reducing time. Therefore, it is significantpractice to efficiently produce realistic scene of light on the water surfaces.There are two questions in most researches on realistic rendering of specularhighlight on the water surfaces. Firstly, the local reflection model for renderingspecular highlight on the water surfaces is not based on inherent characteristic.Secondly, computation of intersections between rays and water waves is veryextensive. Recently, a reflection model for the ocean surface is proposed by Ross torender the light on the water surface. Nevertheless, the model is complex forrendering specular highlight, and needed extensive computation for intersectionsbetween rays and water waves.The work in this paper is as follows:First of all, a method is proposed to quickly render realistic scenes of specularhighlights on a water surface, based on the improved sphere-tracing algorithm and thesimplified Ross reflection model. The water surface is pre-processed, by introducing aquadtree structure and boundary box. In the course of tracing rays, boundary box ismodified iteratively, and increasingly fit to the water surface. The intersectionsbetween the rays and the boundary boxes are regarded as inputs of the sphere-tracingalgorithm. The intersections of specular highlights are then determined according tothe law of specular reflection. The visible interaction probability is simplifiedaccording to the visibility of the intersections, and the simplified Ross reflectionmodel is obtained. Then radiance of the specular highlight intersections is computedusing this model.Secondly, the method proposed above is verified with OpenGL on P43.0GHzcomputer, using visual studio c++2005. Two kinds of scenes including specularhighlight on the water surface are considered. One is for different positions of sun,and the other is for different height of water waves. Experimental results indicate thatthe proposed algorithm enhances computation of the intersections between rays andwater waves, yielding realistic specular highlights on the surfaces of water.