HumanCentric Light Sensing and Estimation From RGBD Images: The Invisible Light Switch Lighting design in indoor environments is of primary importance for at least two reasons: 1) people should perceive an adequate light; 2) an effective lighting design means consistent energy saving. We present the Invisible Light Switch (ILS) to address both aspects. ILS dynamically adjusts the room illumination level to save energy while maintaining constant the light level perception of the users. So the energy saving is invisible to them. Our proposed ILS leverages a radiosity model to estimate the light level which is perceived by a person within an indoor environment, taking into account the person position and herhis viewing frustum (head pose). ILS may therefore dim those luminaires, which are not seen by the user, resulting in an effective energy saving, especially in large open offices (where light may otherwise be ON everywhere for a single person). To quantify the system performance, we have collected a new dataset where people wear luxmeter devices while working in office rooms. The luxmeters measure the amount of light (in Lux) reaching the people gaze, which we consider a proxy to their illumination level perception. Our initial results are promising: in a room with 8 LED luminaires, the energy consumption in a day may be reduced from 18585 to 6206 watts with ILS (currently needing 1560 watts for operations). While doing so, the drop in perceived lighting decreases by just 200 lux, a value considered negligible when the original illumination level is above 1200 lux, as is normally the case in offices.

Simplified Light Probe using Minimal Number of Photodiodes Many display system users have strongly desired that a superimposed virtual object of computer graphics (CG) have optical consistency with a real object at a scene. For this study, we model a realworld light environment as one point light source at infinite distance and an environmental light, which has only three parameters: the point light direction and intensity ratios of the two light sources. We propose a simplified light probe sensor that has five photo IC diodes on each surface of a square pillar, except at its bottom, to estimate the three parameters. The five outputs of the photo IC diode under specific model parameters are obtainable analytically because the directivity characteristics of photo IC diode are approximated as a cosine of the incident angle. The three parameters are then derived from the five outputs. The parameter estimation entails very low computational cost. Experimental results demonstrate sufficient estimation accuracy to render a CG object without a feeling of strangeness.