## 2 Glare Definition and Spatial Characteristics  
The glare calculation method recommended by the International Commission on Illumination (CIE) was used to combine the Einhorn and Hopkinson formulas and the Guth position parameter. The calculated uniform glare index was used to predict the visual impact on the environment from the glare of a light source based on human factors. According to CIE 55-1983 and CIE 119-1995, the CIE Glare Index (CGI) of indoor lighting fixtures is defined as follows [18; 19]  
\[CGI=8 log\left[2\frac{1+\frac{E_{d}}{500}}{E_{d}+E_{i}},\sum\frac{L_{a}{}^{2} \omega_{a}}{P_{a}{}^{2}}\right] \tag{1}\]  
where \(E_{d}\) is the direct vertical illumination of human eyes (direct vertical illuminance, lux), \(E_{i}\) is the indirect illumination on human eyes (indirect illuminance, lux), \(L_{a}\) is the brightness value of a single lamp in the line of sight of the human eye (luminance, nit), \(\omega_{a}\) is the solid angle formed by a single lamp on human eyes (steradian, sr), and \(P_{a}\) is the Guth Position Index of a single luminaire. The Guth position refers to the position of the lamp and the human eye, and it is defined as follows  
\[\frac{1}{P_{a}}=\frac{d^{2}EXP}{d^{2}+1.5d+4.6}+0.12(1-EXP) \tag{2}\]  
where \(EXP\) is defined as follows  
\[EXP=e^{(\frac{-0.185^{2}}{d}+\frac{0.011}{d}^{53})} \tag{3}\]  
where \(d\) is the horizontal distance between the luminaire and the human eye divided by the vertical height between the luminaire and the human eye (forward distance of source/height), and \(S\) is the horizontal distance between the luminaire and the vertical line of sight divided by the vertical height between the luminaire and the human eye (sideways distance of source/height).  
CIE 117-1995 also defines another uncomfortable glare index called the UGR that considers the effect of background brightness on glare. Therefore, the parameters of the background luminance of the environment \(L_{b}\) are added as follows [20]  
\[UGR=8\log\left[\frac{0.25}{L_{b}}\sum\left(\frac{L^{2}\omega_{i}}{p^{2}}\right)\right] \tag{4}\]  
where 8 gives \(UGR\) numbers that optimize and range from approximately 5 to 40, the logarithm (log) is used because human eyes react logarithmically to light, and \(\Sigma\) shows that the equation includes all the fittings located within the area, where \(L_{b}\) is defined as follows:  
\[L_{b}=\frac{E_{ind}}{\pi} \tag{5}\]  
Here, \(L_{b}\) is the value of the background luminance in cd/m\({}^{2}\), \(E_{ind}\) is the vertical indirect illuminance of the viewer's eye, and \(L\) is defined as follows:  
\[L=\frac{I}{A_{p}} \tag{6}\]  
Here, \(L\) is the luminance value of the luminous parts of each luminaire in the direction of the viewer's eye in cd/m\({}^{2}\), \(I\) is the luminaire's luminance, \(A_{p}\) is the project area, and \(\omega_{i}\) is defined as follows:  
\[\omega_{i}=\frac{A_{p}}{r^{2}} \tag{7}\]  
Here, \(\omega_{i}\) is the solid angle of the luminous parts of each luminaire on the viewer's eye in steradian (sr), \(r\) is the distance from the light source to the viewer's eyes, and p is the Guth position index for each individual luminaire that corresponds to its displacement from the line of sight and is related to the horizontal and tangent function of the observer to the light source.  
Uniformity is calculated as follows [21]:  
\[Uniformity=\frac{\text{\emph{minimum illuminance} }(lux)}{\text{\emph{average illuminance} }(lux)} \tag{8}\]