首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2篇
  完全免费   4篇
  自动化技术   6篇
  2011年   2篇
  2008年   2篇
  2007年   2篇
排序方式: 共有6条查询结果,搜索用时 62 毫秒
1
1.
空间动态可变材质的交互式全局光照明绘制   总被引:1,自引:1,他引:0       下载免费PDF全文
SUN Xin  周昆  SHI Jiao-Ying 《软件学报》2008,19(7):1783-1793
提出了一种空间动态可变材质的交互式全局光照明绘制算法.如果在绘制过程中允许用户对物体的材质作修改,并且对一个物体的不同部分的材质作不同的修改,则称为空间动态可变材质.由于最终出射的辐射亮度和材质呈非线性关系,因此现有许多交互式全局光照明算法不允许用户修改物体的材质.如果一个物体各部分的材质可以不相同,那么材质对最终的出射的辐射亮度的影响更为复杂,目前没有任何交互式全局光照明绘制算法能够在绘制过程中对一个物体不同部分的材质作不同的修改.将一个空间动态可变材质区域划分成许多子区域来近似模拟,每个子区域内部材质处处相同.光在场景传播过程中可能先后被不同的子区域反射,并以此将最终出射的辐射亮度分为许多部分.用一组基材质来线性表示所有的材质,这组基材质被赋予场景中的所有子区域,从而得到不同的基材质的分布.预计算所有这些基材质分布下的各部分最终出射的辐射亮度.绘制时根据各子区域材质在基材质上的系数组合相应的预计算数据,就能交互式绘制全局光照明效果.  相似文献
2.
提出一种基于蒙特卡洛积分,利用半球谐函数对光滑平面进行的快速全局照明计算方法.该方法通过在光滑平面上的辐亮度进行取样,然后把其放进高速缓存器中,经过计算再对其它点进行插值.为了提高计算速度,物体表面的入射辐亮度被半球谐化,并且物体表面的双向反射率分布函数也被定义成两个半球面上的笛卡儿积.插值时,利用梯度方向插值,并且用了一种简便的方法来计算一个点的梯度.该方法能极大提高了全局照明的计算速度.这对于照明工程、高质量的动画制作及虚拟现实等领域都具有非常广阔的应用前景.  相似文献
3.
孙鑫  周昆  石教英 《软件学报》2008,19(4):1004-1015
现有的基于预计算的全局光照明绘制算法都假设场景中物体的材质固定不变,这样,从入射光照到出射的辐射亮度之间的传输变换就是线性变换.通过对这种线性变换的预计算,可以在动态光源下实现全局光照明的实时绘制.但是,当材质可以改变时,这种线性变换不再成立,因此,现有算法无法直接用于动态材质的场景.提出了一种方法:在修改场景中的物体材质时,可以实时得到场景在直接光照和间接光照下的绘制效果.将最终到达视点的辐射亮度根据其之前经过的反射次数及相应的反射材质分为多个部分,每个部分和先后反射的材质的乘积成正比,从而把该非线性问题转化为线性问题.又将所有可选的材质都表示为一组基的线性组合.将这组基作为材质赋予场景中的物体,就有各种不同的组合方式,预计算每种组合下所有部分的出射辐射亮度.在绘制时,根据各物体材质投影到基上的系数线性组合预计算的数据就能实时得到最终的全局光照明的绘制结果.该方法适用于几何场景、光照和视点都不发生变化的场景.使用双向反射分布函数来表示物体的材质,不考虑折射或者半透明的情况.该实现最多包含两次反射,并可以实时绘制得到一些很有趣的全局光照明效果,比如渗色、焦散等等.  相似文献
4.
顾耀林  朱丽华  王华 《计算机应用》2007,27(7):1626-1628
对虚拟图像场景绘制算法进行研究,提出了一种基于低维线性子空间的球面谐波光照表示算法.从物体模型得到子空间,并抽取其中的低维线性空间,利用球面谐波函数将朗伯反射作为一个卷积处理,来近似表示朗伯反射,同时添加了漫反射阴影交互转移.实验结果表明该算法逼近程度好,绘制质量高,具有一定的实用价值.  相似文献
5.
This paper presents a comprehensive and efficient framework for computer-aided appearance design based on BRDF (bidirectional reflectance distribution function) measurements. It covers all stages of a new product development including acquisition, processing and modeling of reflectance data, interactive rendering and evaluation of material appearance, and manufacturing operations. The proposed method eliminates the need of making a real physical prototype by providing a reliable surface appearance design process in which he/she can faithfully simulate the final surface appearance in the early design stage of a product. In addition, it enables us to manufacture the coating surface the same as the computer simulated surface from the known coating specification. The accuracy test between a real sample and the computer simulated one demonstrates that the proposed method satisfies an acceptable level of accuracy for industrial applications. A case study has been conducted to evaluate the user preference on the surface appearance of a digital handheld device which contains a combination of different coating surfaces. The case study successfully demonstrates that the user preference can be identified using the proposed method while changing the combination of different coating surfaces represented by BRDFs considering factors such as surrounding environments and age groups.  相似文献
6.
In this paper, we investigate the surface-atmosphere radiative interaction in application to the problem of aerosol satellite remote sensing over land. First, we test different models of the Bidirectional Reflectance and Polarization Distribution Function (BRDF and BPDF) for bare soil and vegetation surfaces using multi-angle, multi-spectral photopolarimetric airborne measurements of the Research Scanning Polarimeter (RSP). Then, we investigate the performance of different models of BRDF and BPDF for modeling top-of-atmosphere measurements. We have found that different BRDF models can describe the RSP measurements equally well. However, for soil surfaces, the different BRDF models show a different dependence on illumination geometry (solar zenith and azimuth angles), as well as a different dependence on viewing angle outside the range of RSP measurements. This implies that different models describe the surface-atmosphere interaction differently, leading for soil surfaces to differences in the top-of-atmosphere reflectance up to 4-5%, whereas at surface level the models agree within 2% for RSP illumination and measurement geometry. For vegetation, the different BRDF models show more similar dependence on illumination geometry, meaning that, in general, the differences in top-of-atmosphere reflectances are smaller than the differences in surface total reflectances. For the BPDF, we compare the empirical model of Nadal and Breon (1999) and the model developed by Maignan et al. (2009) with a newly developed model. The latter model compares better with RSP measurements. It was shown that, though all models have essentially different angular profiles at different illumination and viewing geometries, the difference of the top-of-atmosphere degree of linear polarization is less or is of the same order as the degree of linear polarization difference at the surface level taken at RSP illumination and measurement geometry. For the considered models, it can be up to 0.015 but is mostly below 0.005.  相似文献
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号