一种基于图像的非均匀单散射参与介质建模方法  

Image-based modeling of inhomogeneous single-scattering participating media

作　　者：胡勇[1] 齐越[1] 童欣[2] 

机构地区：[1]北京航空航天大学虚拟现实技术弓系统国家重点实验室,北京100191 [2]微软亚洲研究院,北京100080

出　　处：《中国科学：信息科学》2011年第1期12-22,共11页Scientia Sinica(Informationis)

基　　金：国家自然科学基金(批准号:60773153);国家高技术研究发展计划(批准号:2009AA012102);北京市自然科学基金(批准号:4102037)资助项目

摘　　要：针对非均匀单散射参与介质建模问题,提出一种能够保持密度场空间变化细节的建模方法.使用体数据、吸收和散射系数之比分别描述参与介质空间变化的密度分布及光线在其内部的传输特性,通过构建采集图像像素值与它们之间的表达式,将建模问题转化为非线性数值优化问题,求最优解.为了解决高分辨率体数据下大量体素密度值同时求解带来的时间开销大及数值不稳定问题,提出一种符合采集图像像素值明暗分布规律的密度场体数据初始化算法和一种多分辨率体数据逐步求精优化算法;为了快速计算大量体素密度值梯度,提出一种基于GPU的多体素并行梯度计算算法.实验结果表明,提出的方法能够根据采集图像重构烟模型,并保持其细节信息.We propose a method to reconstruct inhomogeneous single-scattering participating media,whichcould preserve fine high-frequency details of density field.Volumetric data and the ratio of absorption coeffcient to scattering coeffcient are used to describe the spatial-varying density distribution and optical properties of certain participating media,and a function between the above parameters and captured pixel values is built.Thus the problem of how to find solutions to these parameters is formulated into a nonlinear numerical optimization problem.In order to reduce large time overheads and numerical instability brought by simultaneously solving large numbers of voxels,we propose an initialization algorithm for enabling the assigned density values to satisfy the regularity of brightness distribution in captured images approximately as well as a progressive refinement algorithm for multi-resolution volumetric data.Besides,we propose a parallel multi-voxel gradient computation algorithm of utilizing hardware acceleration to reduce time overheads in gradient computation for large numbers of voxels.Experiment results indicate that our method is well suited for reconstructing thin smoke,retaining high-frequency details from images captured from multiple viewpoints.

关 键 词：单散射参与介质 烟建模 体数据建模 基于图像的建模 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]