Owing to its generality and efficiency, Cascaded Shadow Maps （CSMs） has an important role in real-time shadow rendering in large scale and complex virtual environments. However, CSMs suffers from redundant rendering...Owing to its generality and efficiency, Cascaded Shadow Maps （CSMs） has an important role in real-time shadow rendering in large scale and complex virtual environments. However, CSMs suffers from redundant rendering problem -- objects are rendered undesirably to different shadow map textures when view direction and light direction are not perpendicular. In this paper, we present a light space cascaded shadow maps algorithm. The algorithm splits a scene into non-intersecting layers in light space, and generates one shadow map for each layer through irregular frustum clipping and scene organization, ensuring that any shadow sample point never appears in multiple shadow maps. A succinct shadow determination method is given to choose the optimal shadow map when rendering scenes. We also combine the algorithm with stable cascaded shadow maps and soft shadow algorithm to avoid shadow flicking and produce soft shadows. The results show that the algorithm effectively improves the efficiency and shadow quality of CSMs by avoiding redundant rendering, and can produce high-quality shadow rendering in large scale dynamic environments with real-time performance.展开更多
Realism rendering methods of outdoor augmented reality(AR)is an interesting topic.Realism items in outdoor AR need advanced impacts like shadows,sunshine,and relations between unreal items.A few realistic rendering ap...Realism rendering methods of outdoor augmented reality(AR)is an interesting topic.Realism items in outdoor AR need advanced impacts like shadows,sunshine,and relations between unreal items.A few realistic rendering approaches were built to overcome this issue.Several of these approaches are not dealt with real-time rendering.However,the issue remains an active research topic,especially in outdoor rendering.This paper introduces a new approach to accomplish reality real-time outdoor rendering by considering the relation between items in AR regarding shadows in any place during daylight.The proposed method includes three principal stages that cover various outdoor AR rendering challenges.First,real shadow recognition was generated considering the sun’s location and the intensity of the shadow.The second step involves real shadow protection.Finally,we introduced a shadow production algorithm technique and shades through its impacts on unreal items in the AR.The selected approach’s target is providing a fast shadow recognition technique without affecting the system’s accuracy.It achieved an average accuracy of 95.1%and an area under the curve(AUC)of 92.5%.The outputs demonstrated that the proposed approach had enhanced the reality of outside AR rendering.The results of the proposed method outperformed other state-of-the-art rendering shadow techniques’outcomes.展开更多
针对当前无人机航空影像阴影角度校正方法存在校正精度和召回率较低,导致无人机航空影像信息的利用价值降低的问题,本文提出了立体测绘型双翼无人机航空影像阴影角度校正方法。以无人机检测到的影像阴影边缘为基础点,计算航空影像色彩...针对当前无人机航空影像阴影角度校正方法存在校正精度和召回率较低,导致无人机航空影像信息的利用价值降低的问题,本文提出了立体测绘型双翼无人机航空影像阴影角度校正方法。以无人机检测到的影像阴影边缘为基础点,计算航空影像色彩空间的色调差参照值和阴影区域的色调分量,根据阴影区域的纹理特征,去除无人机航空影像的阴影;考虑双翼无人机航行的空间位置,将无人机航空影像的RGB(red green blue)色彩空间转换为HSV(hue saturation value)色彩空间,通过无人机航空影像阴影角度的平滑处理,控制无人机航空影像阴影角度;利用灰度线性变化算法与自适应阈值计算法,对无人机航空影像阴影角度进行校正处理,实现对无人机航空影像阴影角度的精确校正,完成无人机航空影像阴影角度的控制与校正算法设计。结果表明:采用本文方法在Txcet-M数据集和Nfteg-H数据集进行航空影像测试,校正精度最高可达99%,召回率最高为98%;在GIswu-K数据集进行测试,得到的校正精度和召回率均在75%以上。这说明利用本文方法可以较好地优化航空影像阴影角度校正性能。展开更多
在局部阴影条件下,常规的最大功率点跟踪MPPT(maximum power point tracking)算法因含有容易陷入局部极值、跟踪精度低等弊端,使其无法及时、精确地跟踪光伏发电系统的最大功率点,因此,提出了一种基于改进型鲸鱼优化算法的光伏发电系统M...在局部阴影条件下,常规的最大功率点跟踪MPPT(maximum power point tracking)算法因含有容易陷入局部极值、跟踪精度低等弊端,使其无法及时、精确地跟踪光伏发电系统的最大功率点,因此,提出了一种基于改进型鲸鱼优化算法的光伏发电系统MPPT控制策略。首先,采用混沌映射初始化种群,增加种群的多样性。其次,通过引入非线性收敛因子使局部寻优能力和全局搜索能力达到均衡。最后,通过引入非线性时变的自适应权重使系统及时跳出局部最优解,并提高搜索的精度。经仿真验证,与粒子群优化算法、狮群优化算法、传统的鲸鱼优化算法等相比,改进的鲸鱼算法在跟踪速度、精度、稳定性等方面均有更显著的效果。展开更多
基金国家重点基础研究发展规划(973)(the National Grand Fundamental Research 973 Program of China under Grant No．2002CB312103)河南省自然科学基金(the Natural Science Foundation of Henan Province of China under Grant No．0611051900)。
基金supported by the National Natural Science Foundation of China under Grant No.60873159Program for New Century Excellent Talents in University under Grant No.NCET-07-0039+1 种基金the National High-Tech Research & Development 863 Program of China under Grant No.2009AA012103the Beijing Municipal Natural Science Foundation under Grant No.4102030
文摘Owing to its generality and efficiency, Cascaded Shadow Maps （CSMs） has an important role in real-time shadow rendering in large scale and complex virtual environments. However, CSMs suffers from redundant rendering problem -- objects are rendered undesirably to different shadow map textures when view direction and light direction are not perpendicular. In this paper, we present a light space cascaded shadow maps algorithm. The algorithm splits a scene into non-intersecting layers in light space, and generates one shadow map for each layer through irregular frustum clipping and scene organization, ensuring that any shadow sample point never appears in multiple shadow maps. A succinct shadow determination method is given to choose the optimal shadow map when rendering scenes. We also combine the algorithm with stable cascaded shadow maps and soft shadow algorithm to avoid shadow flicking and produce soft shadows. The results show that the algorithm effectively improves the efficiency and shadow quality of CSMs by avoiding redundant rendering, and can produce high-quality shadow rendering in large scale dynamic environments with real-time performance.
文摘Realism rendering methods of outdoor augmented reality(AR)is an interesting topic.Realism items in outdoor AR need advanced impacts like shadows,sunshine,and relations between unreal items.A few realistic rendering approaches were built to overcome this issue.Several of these approaches are not dealt with real-time rendering.However,the issue remains an active research topic,especially in outdoor rendering.This paper introduces a new approach to accomplish reality real-time outdoor rendering by considering the relation between items in AR regarding shadows in any place during daylight.The proposed method includes three principal stages that cover various outdoor AR rendering challenges.First,real shadow recognition was generated considering the sun’s location and the intensity of the shadow.The second step involves real shadow protection.Finally,we introduced a shadow production algorithm technique and shades through its impacts on unreal items in the AR.The selected approach’s target is providing a fast shadow recognition technique without affecting the system’s accuracy.It achieved an average accuracy of 95.1%and an area under the curve(AUC)of 92.5%.The outputs demonstrated that the proposed approach had enhanced the reality of outside AR rendering.The results of the proposed method outperformed other state-of-the-art rendering shadow techniques’outcomes.
文摘针对当前无人机航空影像阴影角度校正方法存在校正精度和召回率较低,导致无人机航空影像信息的利用价值降低的问题,本文提出了立体测绘型双翼无人机航空影像阴影角度校正方法。以无人机检测到的影像阴影边缘为基础点,计算航空影像色彩空间的色调差参照值和阴影区域的色调分量,根据阴影区域的纹理特征,去除无人机航空影像的阴影;考虑双翼无人机航行的空间位置,将无人机航空影像的RGB(red green blue)色彩空间转换为HSV(hue saturation value)色彩空间,通过无人机航空影像阴影角度的平滑处理,控制无人机航空影像阴影角度;利用灰度线性变化算法与自适应阈值计算法,对无人机航空影像阴影角度进行校正处理,实现对无人机航空影像阴影角度的精确校正,完成无人机航空影像阴影角度的控制与校正算法设计。结果表明:采用本文方法在Txcet-M数据集和Nfteg-H数据集进行航空影像测试,校正精度最高可达99%,召回率最高为98%;在GIswu-K数据集进行测试,得到的校正精度和召回率均在75%以上。这说明利用本文方法可以较好地优化航空影像阴影角度校正性能。
文摘在局部阴影条件下,常规的最大功率点跟踪MPPT(maximum power point tracking)算法因含有容易陷入局部极值、跟踪精度低等弊端,使其无法及时、精确地跟踪光伏发电系统的最大功率点,因此,提出了一种基于改进型鲸鱼优化算法的光伏发电系统MPPT控制策略。首先,采用混沌映射初始化种群,增加种群的多样性。其次,通过引入非线性收敛因子使局部寻优能力和全局搜索能力达到均衡。最后,通过引入非线性时变的自适应权重使系统及时跳出局部最优解,并提高搜索的精度。经仿真验证,与粒子群优化算法、狮群优化算法、传统的鲸鱼优化算法等相比,改进的鲸鱼算法在跟踪速度、精度、稳定性等方面均有更显著的效果。
