Alternating Physically Based Renderingin Low-lit Areas

Abstract: Background The increase in screen resolution has increased from HD to Ultra-HDduring the last decade. A modern game today with Ultra-HD resolution has overeight million pixels that need to be shaded, combined with the expensive shadingmethod Physically Based Rendering the equations needed to calculate each pixel arenumerous. Objectives This the study aims to remove complexity from the Physically BasedRendering shading method in the form of roughness in low-lit areas. The low-lit areaswill instead be rendered without the roughness attribute. By removing roughnessless calculations will be performed. Methods To remove roughness from low-lit areas the light had to be approximatedusing a diffuse model. The pixel was later converted via Hue Saturation PerceivedBrightness to calculate the brightness. If the pixel was under the given threshold,the pixel was shaded using a low-complexity Physically Based Rendering implemen-tation without roughness. A user study was conducted using Unity game enginewith eight participants being asked to compare different stimuli all rendered withdifferent thresholds for darkness with a reference picture. The aim of the study wasto ascertain if the stimuli without roughness had any perceivable difference from thereference. Results The results of the study show the majority of the participants noticinga difference when comparing the stimuli with the reference. The areas affected wasnot only the low-lit areas but the whole scene. The energy conversion without theroughness value made the whole scene appear darker. Conclusions The roughness value is an integral part of energy conversion andwithout it, the scene will appear much darker. While the majority of participantsnoticed a difference, the lowest threshold resembled the original the most