摘要
针对全局光照下的物理正确软影绘制较难满足交互性的难题,提出体现遮挡对象空间位置远近关系的可变半影近似绘制算法。首先,以光源中心点为参照通过基于光线跟踪的遮挡测试方法生成二值光源可见性图;并提出每个可视场景点对应自适应可见性空间平滑滤波器宽度的确定方法;然后执行带掩模计算的自适应可见性滤波来获得从可见区到非可见区平滑过渡的可见性因子;最后在光线跟踪流程中使用可见性因子动态调制相应可视场景点不考虑遮挡的直接光照值,再加上间接光照得到高真实感软影。实验结果表明:该算法效果与物理正确阴影在柔和度方面非常接近,容易绘制镜面反射间接光照,且测试场景的帧率在30帧/秒以上,满足交互性要求。
Focusing on the difficulty in interactively rendering physically correct soft shadows existing in global illumination effects,this study proposes an algorithm for producing approximate soft shadows,which can generate alterable penumbra reflecting spatial positions of occluders.Firstly,a binary light-visibility map is generated by using occluding detection method based on ray tracing and taking the center of light source as a reference point.Secondly,a way that adaptively determines the kernel size of spatial smoothing filter is proposed.Then,visibility factors that change smoothly from visible region to non-visible region are obtained by a method of adaptive visibility filtering.The filtering method can solve the problem of visibility infiltration by using mask.Finally,the visibility factors are used to dynamically modulate the direct illumination of the associated visible points in the process of ray tracing.The highly realistic soft shadow effects are produced by adding the modulated direct illumination and ordinary indirect illumination together.Experimental results show that the algorithm is fully compatible with ray tracing and hence is easy to compute indirect illumination including mirrored visual effects.The soft shadows in images generated by our method look like physically-correct soft shadows.The rendering speed of our method is beyond 30 frames per second for all test scenes featuring specular reflections,hence satisfying the requirements of interactive applications.
作者
杨超智
陈纯毅
曲福恒
陈胜
邢琦玮
YANG Chao-zhi;CHEN Chun-yi;QU Fu-heng;CHEN Sheng;XING Qi-wei(School of Computer Science and Technology,Changchun University of Science and Technology,Changchun Jilin 130022,China)
出处
《图学学报》
CSCD
北大核心
2019年第1期165-172,共8页
Journal of Graphics
基金
吉林省科技发展计划项目(20170101005JC
20180519012JH)
吉林省省级产业创新专项资金项目(2016C091)
吉林省教育厅"十三五"科学技术项目(JJKH20170629KJ
JJKH20181136KJ)
关键词
软影
可变半影
光源可见性
光线跟踪
自适应滤波
soft shadows
variable penumbra
light-source visibility
ray tracing
adaptive filtering
