武装直升机红外辐射计算中多重遮挡处理

针对武装直升机红外辐射计算中任意方向上可视净面积求取问题,提出了一种基于随机模拟的遮挡处理方法.该方法利用曲面造型方法建立直升机的三维模型,并将其离散为四边形面元,采用翼边拓扑结构描述直升机外形的数学模型.在此基础上,基于可见性测试、深度测试和遮挡测试原理对空间多边形面元进行遮挡判断,求出其遮挡面元集,再利用随机变量的统计方法对该多边形进行遮挡计算,求得净面积.对某型武装直升机和简单形体的计算表明,通过合理划分面元数和选取随机点数, 简单目标计算误差可以控制在5%以内,复杂目标可以控制在工程精度要求内.该方法已应用于武装直升机红外辐射特性计算软件中,应用表明该方法稳定、可靠,适于工程分析. 

New algorithm of processing multi occultation and its application in infrared radiation calculation of military helicopter

To solve the problem of calculating visible net area under any direction in infrared radiation calculation for military helicopter,a new algorithm based on stochastic simulation was proposed.By using surface modeling method, the helicopter's three-dimensional model was constructed and discretilized into quad surface elements.The mathematic model for helicopter was represented with the winged-edge structure.Visibility test,depth test and shelter test were applied to find out all the other polygons that have occultation relationship with the researched spatial polygon,then put them into a set.The statistics method of random variable was introduced subsequently to calculate the net area of this polygon.The calculation results of certain military helicopter and simple object show that the percentage error for simple object can be controlled within 5%,and for complex object can meet the engineering requirement by controlling the total polygons and random points reasonably.The algorithm has been used successfully in the calculation software of military helicopter 's infrared radiation. Applications show that the algorithm is stable,reliable and suitable for engineering analyses.