Relighting Photographs of Tree Canopies
Relighting Photographs of Tree Canopies
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DOI：
10.1109/tvcg.2010.236
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发表时间：
2011-10-01
影响因子：
5.2
通讯作者：
Drettakis, George
中科院分区：
文献类型：
--
作者：
Cabral, Marcio;Bonneel, Nicolas;Drettakis, George
我们提出了一种基于图像的方法来重新照亮树冠的照片。我们的目标是最大限度地减少捕获开销；因此，唯一需要的输入是在一天中的某个时间拍摄的一组树木照片，同时允许在任何其他时间重新照明。我们首先从理论上和使用模拟来分析树冠中的照明。从这个分析中，我们观察到树冠照明与体积照明相似。我们假设树冠采用单散射体积照明模型，并采用漫叶反射率；我们通过合成效果图验证了我们的假设。我们根据一天中某个时间拍摄的 10-12 张图像创建树的体积表示，并使用单散射参与媒体照明模型。分析太阳和天空照明模型为捕获的输入和未知目标时间提供一致的照明表示。我们通过应用目标和输入时间照明表示的比率来重新照亮输入图像。我们通过以球谐函数同时编码从天空到眼睛的透射率来有效地计算这种表示。我们通过重新照亮合成树的图像并与路径追踪解决方案进行比较来验证我们的方法。我们还提供照片结果，并用延时地面实况序列进行验证。
We present an image-based approach to relighting photographs of tree canopies. Our goal is to minimize capture overhead; thus the only input required is a set of photographs of the tree taken at a single time of day, while allowing relighting at any other time. We first analyze lighting in a tree canopy both theoretically and using simulations. From this analysis, we observe that tree canopy lighting is similar to volumetric illumination. We assume a single-scattering volumetric lighting model for tree canopies, and diffuse leaf reflectance; we validate our assumptions with synthetic renderings. We create a volumetric representation of the tree from 10-12 images taken at a single time of day and use a single-scattering participating media lighting model. An analytical sun and sky illumination model provides consistent representation of lighting for the captured input and unknown target times. We relight the input image by applying a ratio of the target and input time lighting representations. We compute this representation efficiently by simultaneously coding transmittance from the sky and to the eye in spherical harmonics. We validate our method by relighting images of synthetic trees and comparing to path-traced solutions. We also present results for photographs, validating with time-lapse ground truth sequences.