实时绘制中的阴影贴图反走样算法研究

摘要

Shadow is an effective method for enhancing scene’ s realism in real-time rendering, and the shadow mapping is the most widely used dynamic shadows real-time rendering currently, but has the image method-based inherent drawback of aliasing inevitably.In the paper we analyse the types and the causes of aliasing in existing shadow mapping algorithms.According to the influence factors of aliasing, it has to improve the sampling rate of the screen on the depth texture if to weaken the shadow boundary aliasing is expected.Based on this idea, we design and realise a new anti-aliasing method for shadow mapping which is based on spatial parallel-split, propose a new scene division approachby integrating the advantages of logarithmic split and average split, and design the coordinate transformation method for circumscribed sphere.Finally we develop the prototype system for carrying out the experimental analysis on the developed shadow mapping anti-aliasing algorithms.Experimental results show that, under the premise of satisfying the demand of real-time rendering efficiency, the method used in this paper can be an effective solution to the shadow aliasing and can improve the effect of scene rendering.%阴影是实时绘制中增强场景真实感的有效方法，阴影贴图是目前应用最广泛的动态阴影实时绘制方法，但不可避免地具有基于图像方法的固有走样缺点。分析已有阴影贴图算法中走样的种类与成因，根据走样的影响因素，要想减弱阴影边界走样，就必须提高屏幕对深度纹理的采样率。基于此思路，设计并实现一种基于空间平行分割的新的阴影贴图反走样方法，综合对数分割与平均分割的优点提出新的场景划分方法，并设计外接球的坐标变换方法，最后开发了原型系统对所开发的阴影贴图反走样算法进行实验分析。实验结果表明，在满足实时绘制效率需求的前提下，采用的方法可以有效解决阴影走样问题，改进场景的绘制效果。