基于Microfacet理论,当光线照射到粗糙表面时会发生显著的多次镜面反射现象,而传统偏振双向反射分布函数(Polarized Bidirectional Reflectance Distribution Function,pBRDF)未能很好地描述这种现象,为了得到更精确的pBRDF模型,更好地...基于Microfacet理论,当光线照射到粗糙表面时会发生显著的多次镜面反射现象,而传统偏振双向反射分布函数(Polarized Bidirectional Reflectance Distribution Function,pBRDF)未能很好地描述这种现象,为了得到更精确的pBRDF模型,更好地分析材料的偏振特性,本文在包含镜面反射、漫反射和定向漫反射的三分量pBRDF模型基础上,进一步定义了高阶微相位角与一阶相位角的关系。改进后的pBRDF模型不仅考虑了多次镜面反射的几何衰减因子,还引入了微相位角的定义,从而建立了一个更全面的高阶镜面反射pBRDF模型。通过比较不同的pBRDF模型,并结合偏振特性采集装置进行验证,实验结果表明,本文提出的模型优于其他模型,三阶模型效果普遍优于二阶。在偏振图像渲染中,峰值信噪比和结构相似性平均分别提升10.09%和2.97%,呈现更加真实的渲染效果。验证本文提出的高阶镜面反射pBRDF模型能够更准确地描述目标表面的偏振特性。展开更多
Many real-life materials have sparkling appearances.Some small flakes on the surface of an object can make a considerable contribution by reflecting or refracting light at a particular angle,eventually causing a spark...Many real-life materials have sparkling appearances.Some small flakes on the surface of an object can make a considerable contribution by reflecting or refracting light at a particular angle,eventually causing a sparkling appearance.Most existing approaches have focused on the glinty effects on reflective surfaces.However,transparent glint rendering has not been well studied,even though there are many natural phenomena(e.g.,frost)in the real world.Recent studies have proposed the simulation of transparent glints under specific constraints(e.g.,limited to the Beckmann distribution and V-groove shadowing-masking function).In this study,we propose a more general transparent glint model by performing a four-dimensional hierarchical search to count the particles located in the pixel footprint and cone around the refracted ray.Our method can produce transparent glint appearances for arbitrary normal distribution functions(e.g.,GGX or Beckmann)and converge to a smooth microfacet model with a large particle count.展开更多
现有几何光学方法的二向反射分布函数BRDF(bidirectional reflection distribution function)模型在计算阴影遮蔽效应时普遍应用Blinn几何衰减效应假设,其等倾角V形槽近似得出的分段折线形式的几何衰减因子导致BRDF曲线存在较大的误差....现有几何光学方法的二向反射分布函数BRDF(bidirectional reflection distribution function)模型在计算阴影遮蔽效应时普遍应用Blinn几何衰减效应假设,其等倾角V形槽近似得出的分段折线形式的几何衰减因子导致BRDF曲线存在较大的误差.基于倾斜角随机高斯分布的微面元理论提出了一种新的几何衰减模型,得出了积分形式的几何衰减因子表达式,数值模拟比较了Blinn几何衰减因子与修正后的积分型衰减因子以及对应的BRDF模型曲线.结果表明:提出的几何衰减因子在物理合理性以及模拟精度方面都有明显提升,使BRDF模型曲线与已有BRDF数据之间的标准误差由0.0636减小到0.0084.展开更多
This paper proposes a lightweight bidirectional scattering distribution function(BSDF)model for layered materials with anisotropic reflection and refraction properties.In our method,each layer of the materials can be ...This paper proposes a lightweight bidirectional scattering distribution function(BSDF)model for layered materials with anisotropic reflection and refraction properties.In our method,each layer of the materials can be described by a microfacet BSDF using an anisotropic normal distribution function(NDF).Furthermore,the NDFs of layers can be defined on tangent vector fields,which differ from layer to layer.Our method is based on a previous study in which isotropic BSDFs are approximated by projecting them onto base planes.However,the adequateness of this previous work has not been well investigated for anisotropic BSDFs.In this paper,we demonstrate that the projection is also applicable to anisotropic BSDFs and that the BSDFs are approximated by elliptical distributions using covariance matrices.展开更多
文摘基于Microfacet理论,当光线照射到粗糙表面时会发生显著的多次镜面反射现象,而传统偏振双向反射分布函数(Polarized Bidirectional Reflectance Distribution Function,pBRDF)未能很好地描述这种现象,为了得到更精确的pBRDF模型,更好地分析材料的偏振特性,本文在包含镜面反射、漫反射和定向漫反射的三分量pBRDF模型基础上,进一步定义了高阶微相位角与一阶相位角的关系。改进后的pBRDF模型不仅考虑了多次镜面反射的几何衰减因子,还引入了微相位角的定义,从而建立了一个更全面的高阶镜面反射pBRDF模型。通过比较不同的pBRDF模型,并结合偏振特性采集装置进行验证,实验结果表明,本文提出的模型优于其他模型,三阶模型效果普遍优于二阶。在偏振图像渲染中,峰值信噪比和结构相似性平均分别提升10.09%和2.97%,呈现更加真实的渲染效果。验证本文提出的高阶镜面反射pBRDF模型能够更准确地描述目标表面的偏振特性。
基金supported by the National Key R&D Program of China under Grant No.2022ZD0116305the National Natural Science Foundation of China underGrant Nos.62172220 and 62272275.
文摘Many real-life materials have sparkling appearances.Some small flakes on the surface of an object can make a considerable contribution by reflecting or refracting light at a particular angle,eventually causing a sparkling appearance.Most existing approaches have focused on the glinty effects on reflective surfaces.However,transparent glint rendering has not been well studied,even though there are many natural phenomena(e.g.,frost)in the real world.Recent studies have proposed the simulation of transparent glints under specific constraints(e.g.,limited to the Beckmann distribution and V-groove shadowing-masking function).In this study,we propose a more general transparent glint model by performing a four-dimensional hierarchical search to count the particles located in the pixel footprint and cone around the refracted ray.Our method can produce transparent glint appearances for arbitrary normal distribution functions(e.g.,GGX or Beckmann)and converge to a smooth microfacet model with a large particle count.
文摘现有几何光学方法的二向反射分布函数BRDF(bidirectional reflection distribution function)模型在计算阴影遮蔽效应时普遍应用Blinn几何衰减效应假设,其等倾角V形槽近似得出的分段折线形式的几何衰减因子导致BRDF曲线存在较大的误差.基于倾斜角随机高斯分布的微面元理论提出了一种新的几何衰减模型,得出了积分形式的几何衰减因子表达式,数值模拟比较了Blinn几何衰减因子与修正后的积分型衰减因子以及对应的BRDF模型曲线.结果表明:提出的几何衰减因子在物理合理性以及模拟精度方面都有明显提升,使BRDF模型曲线与已有BRDF数据之间的标准误差由0.0636减小到0.0084.
基金supported by the JST ACCEL(JPMJAC1602)JSPS KAKENHI(JP17H06101,18K18075,and JP19H01129).
文摘This paper proposes a lightweight bidirectional scattering distribution function(BSDF)model for layered materials with anisotropic reflection and refraction properties.In our method,each layer of the materials can be described by a microfacet BSDF using an anisotropic normal distribution function(NDF).Furthermore,the NDFs of layers can be defined on tangent vector fields,which differ from layer to layer.Our method is based on a previous study in which isotropic BSDFs are approximated by projecting them onto base planes.However,the adequateness of this previous work has not been well investigated for anisotropic BSDFs.In this paper,we demonstrate that the projection is also applicable to anisotropic BSDFs and that the BSDFs are approximated by elliptical distributions using covariance matrices.
