ABSTRACT

The concept of illumination vector quantities at a given point in three-dimensional space has been proposed since long time ago, but it is mostly described for scenes with point light sources. In real scenes with area light sources, numerical approximations are required to estimate the illumination vector quantities, which can be done by discretising the area into an array of point sources. Two different approaches are proposed in this study; Approach 1 is applicable in the design phase, where the positions of the source and receiver point are exactly known. Approach 2 is applicable during field measurement, based on the obtained cubic illuminances. This study aims to determine the required number of point source elements in the computation and to investigate the difference between both calculation approaches. The proposed concept is demonstrated using a scenario with horizontal, square source and a scenario with vertical, rectangular source, with various luminous intensity distribution patterns, by observing various illumination vector quantities. Grid sensitivity analyses suggest that the largest grid size satisfying the five-to-one approximation rule shall yield quantities that converge within no more than 5% to the final value. For a given size of area source, at a given distance, the differences of illumination vector quantities obtained from both calculation approaches are expected to be approximately the same, regardless the luminous intensity distribution. The estimation of cylindrical illuminance is generally more accurate than that of scalar illuminance.

摘要

很久以前就提出了三维空间中给定点的光照向量的概念，但主要是针对点光源的场景来描述的。在具有区域光源的真实场景中，需要数值近似来估计光照向量，这可以通过将区域离散为点源阵列来完成。本研究提出了两种不同的方法；方法 1 适用于设计阶段，其中源和接收点的位置是完全已知的。方法 2 适用于现场测量，基于获得的立方照度。本研究旨在确定计算中所需的点源元素数量，并研究两种计算方法之间的差异。通过观察各种照明矢量，使用具有水平方形光源的场景和具有垂直矩形光源的场景以及具有各种发光强度分布模式的场景来演示所提出的概念。网格敏感性分析表明，满足五比一近似规则的最大网格尺寸应产生收敛于最终值不超过 5% 的量。对于给定大小的面源，在给定距离处，无论发光强度分布如何，从两种计算方法获得的照明矢量量的差异预计大致相同。圆柱照度的估计通常比标量照度的估计更准确。矩形光源，具有各种发光强度分布图案，通过观察各种光照矢量量。网格敏感性分析表明，满足五比一近似规则的最大网格尺寸应产生收敛于最终值不超过 5% 的量。对于给定大小的面源，在给定距离处，无论发光强度分布如何，从两种计算方法获得的照明矢量量的差异预计大致相同。圆柱照度的估计通常比标量照度的估计更准确。矩形光源，具有各种发光强度分布图案，通过观察各种光照矢量量。网格敏感性分析表明，满足五比一近似规则的最大网格尺寸应产生收敛于最终值不超过 5% 的量。对于给定大小的面源，在给定距离处，无论发光强度分布如何，从两种计算方法获得的照明矢量量的差异预计大致相同。圆柱照度的估计通常比标量照度的估计更准确。网格敏感性分析表明，满足五比一近似规则的最大网格尺寸应产生收敛于最终值不超过 5% 的量。对于给定大小的面源，在给定距离处，无论发光强度分布如何，从两种计算方法获得的照明矢量量的差异预计大致相同。圆柱照度的估计通常比标量照度的估计更准确。网格敏感性分析表明，满足五比一近似规则的最大网格尺寸应产生收敛于最终值不超过 5% 的量。对于给定大小的面源，在给定距离处，无论发光强度分布如何，从两种计算方法获得的照明矢量量的差异预计大致相同。圆柱照度的估计通常比标量照度的估计更准确。