Towards realistic lighted virtual environments in head-mounted displays: transfer functions effects on luminance representation

Immersive virtual reality can be considered one of the most promising technologic for developing lighting design to satisfy the standard requirements and users’ satisfaction. In this process, the deep knowledge of the relation between the digital input values to the frame buffer that controls the software, and the head-mounted displays output is crucial in affecting the users' perception. This paper presents the preliminary results of a comparison between the luminance values in the Unreal Engine 4.27 and an HTC Vive Pro head-mounted display. A simple physical environment was modelled to find the relationship between the luminance values calculated by the software and those shown by the head-mounted display. The absolute luminance values and the luminance ratios were explored by varying the number of luminaires turned on and the luminous flux. In addition, the effect of the tone mapping operator on the luminance values shown by the head-mounted display was also investigated. Results highlight that: i) tone mapping does not influence luminance values obtained in the game engine, and ii) disabling tone mapping allows showing virtual scenes in the head-mounted display whose luminance values and luminance ratios are linearly correlated with those obtained in the Unreal Engine.