Underwater shadow generation based on GPU

Common shadow techniques fail to render the distorted shadow underwater caused by water refraction. We introduce an efficient shadow algorithm for generating underwater shadow, which is implemented on GPU by taking the advantage of its parallelism. By the algorithm, first a shadow map is generated by common shadow techniques. Then the refracted shadow rays from each shadow pixels on the shadow map are determined by a simplified refraction formula that can be evaluated quickly. Finally the underwater shadow map is rendered by approximating the intersection points between shadow rays and underwater terrain based on the continuity of the underwater geometry. Experimental result shows that the algorithm can generate visually plausible underwater shadow in high frame rate, and is suitable for the applications such as 3D games where critical real time performance is demanded.