摘要
针对室外场景的光源方向估计难题,提出一种基于阴影的方法.首先,利用阴影检测方法分离图像中前景的阴影区域,计算只与光照有关而与背景反射属性无关的阴影亮度比(BR),得到阴影区域内具有BR极小值的像素点的拟合直线;其次,根据阴影区域中各点的光照强度与阴影中的位置密切关联的性质,利用BR拟合直线、物体几何高度线和入射光线进行投影建模,并估计光源方向;最后,对已知光源方向真实值的室内场景实验、室外场景实验以及与现有方法进行对比,结果表明,文中方法不需要复杂的图像分割就能够有效地估计出光源方向.
A method is proposed to estimate illumination direction from cast shadows in images of outdoor scenes. First, shadow areas in the foreground are separated using a shadow detection method, and the brightness rate （BR）, which is independent of reflection properties of the material but dependent on illumination intensity onto the material, is computed in shadow areas. A BR line is fitted onto the points that have minimal BR values. Second, based on the property that illumination intensity at the points in a cast shadow area varies depending on their locations, illumination direction is estimated by modeling the height of the object, incident rays from the source of the illumination, and the BR line. Finally, experiments with known illumination direction in indoor scenes, experiments in outdoor scenes, and comparative analyses are carried out. The results show that our method enables illumination direction to be estimated accurately and efficiently, without complicated image segmentation.
出处
《计算机辅助设计与图形学学报》
EI
CSCD
北大核心
2012年第11期1471-1476,1484,共7页
Journal of Computer-Aided Design & Computer Graphics
基金
回国留学人员科研启动基金(20102242358)
回国留学人员科研项目(521294022)
国家"核高基"重大专项(2009ZX01038-001-08)
浙江大学CAD&CG国家重点实验室开放课题(A1011)
关键词
光源方向估计
阴影
阴影亮度比
室外场景
estimating illumination direction
shadow
brightness rate
outdoor scenes
