Research Of Luminance-based Lighting Environment Characterization Method

With the continuous improvement of people's requirements for the quality of light environment,the purpose of light environment design is not only to illuminate space,but to pay more attention to the relationship between people and light.At present,the design of light environment is based on illuminance.Illuminance only represents the amount of light received by the illuminated surface,it is unable to establish the relationship between the light environment and human eye directly,such as human eye perception of glare,so the characterization of light environment based on illuminance can not meet the needs of light environment design.Luminance can represent the intensity of light perceived by the human eye and directly reflect the perception of brightness of the light environment.Therefore,the characterization of light environment based on luminance has gradually attracted people's attention.At present,the problem of the characterization of light environment based on luminance is that the calculation and measurement of luminance are complex.To this end,this paper mainly carries out the following research:(1)Based on the spectral radiance,the bi-directional scattering distribution function(BSDF)of the material and the observation direction,the luminance calculation equation is deduced.In order to calculate the luminance data of the visual plane,this paper studies the physical process of light from the light source to the human eye through multiple reflections and refractions on the surface of the object.Combining with the luminance calculation equation,a luminance-based characterization method of the light environment is established.(2)The luminance-based lighting environment characterization method is programed in this paper.The main work includes the programming of light source,ray,object,material and camera,and the realization and optimization of ray tracing algorithm.The light environment scene is modeled by creating objects with material and light source and then adding them to the scene.When luminance calculation is completed,the storage unit in the camera stores the luminance data of the camera shooting direction.(3)Two ray tracing algorithms are proposed in this paper.One is full-space sampling and tracking algorithm.For achieving accurate brightness calculation,this algorithm must emit enough sampled light,which results in slow calculation speed of software.Based on this,According to Monte Carlo importance sampling,a separate importance sampling and tracking algorithm is proposed,which greatly improves the speed of software calculation reasonably by reduces the number of ray samples.In order to verify the error of software calculation,this paper designs a contrast experiment using standard light source lamp-box.By comparing the luminance data taken by plane luminance meter with the luminance data calculated by software simulation,theexperimental result shows that the mean error is less than 20%,and with the increase of sampling recursive depth,the error further decreases?(4)Taking lighting design of classroom as an example,this paper further analyses the application of plane luminance data by creating classroom lighting scenes and calculating plane luminance data through software,and shows the application prospects of luminance-based lighting environment characterization method.