Screen Space Anisotropic Blurred Soft Shadows by Efficient Separable Filtering Method

Abstract

Shadow mapping is an efficient method to generate shadows in real time computer graphics and has broad variations from hard to soft shadow synthesis. Soft shadowing based on shadow mapping is a blurring technique on a shadow map or on screen space. Blurring on screen space can easily combine with a deferred shading pipeline. However, blurring on screen space has a drawback: the generated shadow is not correct when a view direction has a large angle to the normal of the shadowed plane. In this paper, we introduce a new screen space based method for soft shadowing that is faster and generates more accurate soft shadows than the previous screen space soft shadow mapping method. The resultant images show shadows by our method just stand in the same place, while shadows by the previous method change in terms of penumbra while the view moves. Surprisingly, although our method is more complex than the previous method, the measurement of the calculation time shows our method is also faster than the previous method. This is because our method controls the blurring area more accurately and thus successfully reduces multiplications for blurring.